Landscapes of the Anthropocene with Google Earth 3031453840, 9783031453847

Citation preview

Andrew Goudie

Landscapes of the Anthropocene with Google Earth

Landscapes of the Anthropocene with Google Earth

Andrew Goudie

Landscapes of the Anthropocene with Google Earth

Andrew Goudie School of Geography and the Environment Oxford University Oxford, UK

ISBN 978-3-031-45384-7 ISBN 978-3-031-45385-4  (eBook) https://doi.org/10.1007/978-3-031-45385-4 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland Paper in this product is recyclable.

Preface

Since I was a boy I have had a fascination for landforms and landscapes and this is why I became a geomorphologist. This fascination has grown by the new view of Earth that one gets from space. Google Earth, in particular, provides images of great beauty. I owe a huge debt of gratitude to Google Earth for all the satellite images used in this book and to Dr. Robert Doe of Springer for encouraging me to write it. Oxford, UK 2023

Andrew Goudie

v

Contents

1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Google Earth and Landscapes—Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 1.2 The Anthropocene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 The Palaeoanthropocene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 The Great Acceleration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 1 1 3 6 9

2

Driving Forces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Demographical Developments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Farming. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Fires. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Deforestation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 Urbanisation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 Mining. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 Energy Sources and the Landscape. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9 Tourism. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.10 Climate Change. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13 13 13 15 22 24 28 32 42 49 50 51

3

Humanly-Made Landforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Tells and Other Mounds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Tumuli. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Causewayed Enclosures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 Hillforts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 Defensive Walls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7 Moated Settlements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 Qanat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.9 Terraces and Lynchets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.10 Mine Spoil Heaps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.11 Craters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.12 Ponds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.13 Conclusion: Earth Moving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

53 53 53 55 57 57 59 60 60 61 63 63 66 66 69

4 Rivers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Dams and Barriers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Interbasin Water Transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Channelisation and Straightening. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Levees and Dykes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Flood Relief Channels or Bypasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

73 73 73 75 77 78 79 vii

viii

Contents

4.7 Canals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8 Changes in River Channels as a Result of Land Use Changes. . . . . . . . . . . . 4.8.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8.2 Diversity of Causes: Some Examples . . . . . . . . . . . . . . . . . . . . . . . 4.8.3 Role of Soil Conservation Measures. . . . . . . . . . . . . . . . . . . . . . . . 4.8.4 Role of Invasive Plants and of Animals. . . . . . . . . . . . . . . . . . . . . . 4.8.5 The Role of Mining. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8.6 Water Mills. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8.7 Effects of Urbanisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8.8 Effects of Transport Corridors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9 Holocene and Anthropocene Floodplain Sedimentation. . . . . . . . . . . . . . . . . 4.10 Recent Changes in Sediment Loads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.11 Fluvial Wetland Drainage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.12 River Deltas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13 Flooding and Runoff Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13.1 Groundwater Depletion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13.2 Forest Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13.3 Afforestation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13.4 Riparian Vegetation and the Spread of Invasive Plants. . . . . . . . . . 4.13.5 Swamp Encroachment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13.6 Land Drainage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13.7 Urbanisation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13.8 Permafrost Melting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13.9 Recent Climate Changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.14 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

80 82 82 82 84 84 86 86 89 90 90 92 93 93 97 97 97 98 98 99 99 99 100 101 104 104

The Cryosphere. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Snowpack Disappearance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Permafrost Disruption and Thermokarst. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Valley Glaciers and Small Ice Caps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 Glacial Lakes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 Polar Ice Sheets and Ice Caps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

113 113 113 113 116 122 123 125 125

6 Coasts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Introduction: Coastal Modification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Deliberately Created Landforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.1 Coastal Defence Structures, Groynes, Tsunami Walls, etc.. . . . . . . 6.2.2 Artificial Islands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.3 Artificial Reefs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.4 Salt Pans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.5 Coastal Reclamation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Non-deliberate Changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.1 Accelerated Coastal Erosion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.2 Changing Salt Marshes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.3 Mangroves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.4 Coral Reefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.5 Estuaries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 The Future. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.1 The Amount of Sea Level Rise by 2100 . . . . . . . . . . . . . . . . . . . . . 6.4.2 Land Subsidence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

129 129 129 129 132 132 132 132 134 134 139 142 143 147 147 147 148

5

Contents

ix

6.4.3 Reefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.4 Salt Marshes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.5 Mangroves and Forested Wetlands . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.6 Sabkhas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.7 Cliffed Coasts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.8 Sandy Beaches. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

149 150 151 152 153 153 157 157

7 Lakes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Lake Contraction Due to Reclamation and Sedimentation. . . . . . . . . . . . . . . 7.3 Lake Desiccation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.1 Aral Sea, Central Asia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.2 The Caspian Sea. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.3 The Dead Sea. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.4 Lakes Urmia and Bakhtegan, Iran. . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.5 Lop Nor, China . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.6 East African Lakes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.7 Salton Sea, USA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.8 Owens Lake. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.9 The Great Salt Lake. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

163 163 163 164 165 167 167 167 167 168 168 170 174 174 174

8

Ground Subsidence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Subsidence Due to Changing Groundwater Conditions. . . . . . . . . . . . . . . . . 8.3 Solutional Collapse of Salt and Gypsum . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4 General Subsidence Due to Groundwater Exploitation . . . . . . . . . . . . . . . . . 8.5 Coal Mining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6 Salt Mining by Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.7 Hydrocarbon Abstraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.8 Geothermal Fluid Abstraction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.9 Induced Seismic Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.10 Shrinkage of Organic Soils and Peats. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.11 Hydrocompaction of Collapsing Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.12 Ground Fissures (Earth Fissures). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.13 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

177 177 177 179 180 181 183 184 184 185 185 186 186 187 187

9

Water Erosion and Mass Movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1 Introduction: Soil Erosion by Water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 Long-Term Rates of Erosion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3 Forest Removal and Other Land Use Changes. . . . . . . . . . . . . . . . . . . . . . . . 9.3.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.2 Mid-Latitude Humid Regions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.3 The Tropics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.4 Mediterranean Land Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4 Mechanisms of Soil Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.1 Soil Loss During Harvesting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.2 Erosion by Land Levelling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.3 Tillage Erosion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.4 Grazing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

191 191 192 193 193 194 194 196 197 197 198 198 198

x

Contents

9.4.5 Grassland Replacement by Shrublands. . . . . . . . . . . . . . . . . . . . . . 9.4.6 Irrigation-Induced Erosion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.7 Fire Induced Erosion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.8 Urbanisation, Construction, and Roads. . . . . . . . . . . . . . . . . . . . . . 9.5 Peat Erosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6 Arroyos, Lavakas, Dongas, and Calanchi. . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7 Soil Conservation and Erosion Management. . . . . . . . . . . . . . . . . . . . . . . . . 9.8 Slopes: Accelerated Mass Movements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8.2 Deforestation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8.3 Roads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8.4 Mining. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8.5 Irrigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8.6 Dam Construction: The Case of Vaiont. . . . . . . . . . . . . . . . . . . . . . 9.8.7 Slopes, Glacier Retreat, and Permafrost . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

199 199 199 200 201 203 205 206 206 207 207 207 209 209 211 212

10 Aeolian Anthropocene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2 Dust Storms and Wind Erosion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.2 Desiccation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.3 History of Dust Storms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.4 Dust Storms Since the Mid-Twentieth Century. . . . . . . . . . . . . . . . 10.2.5 Humans or Climate? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.6 Dust Storm Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3 Sand Dunes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.2 Examples of Dune Modification . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.3 Dune Stabilisation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4 Future Anthropocene Climate Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

221 221 221 221 222 223 224 224 225 225 225 228 229 231 233 233

11 Stage 3 of the Anthropocene—Stewardship. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

239 239 244 244

Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

About the Author

ndrew Goudie, Ph.D., D.Sc. Emeritus Professor of A Geography at the University of Oxford, former Pro-ViceChancellor, Honorary Fellow of Hertford College, and former Master of St. Cross College, is a Geomorphologist who led the Kimberley Research Project in 1988. He is a recipient of a Royal Medal from the Royal Geographical Society, the Mungo Park Medal of the Royal Scottish Geographical Society, and the Farouk El-Baz Award of the Geological Society of America. He is Fellow of the British Society of Geomorphologists. He has been Chair of the British Geomorphological Research Group, President of the Geographical Association, and President of the International Association of Geomorphologists. He has written extensively on the human impact and the Anthropocene.

xi

1

Introduction

Abstract

This chapter starts with an introduction to Google Earth and its value for investigating landscapes since it was launched in 2005. This is followed by a discussion of the Anthropocene concept which was introduced in 2002, the Palaeoanthropocene, and the Great Acceleration (post c 1950).

Keywords

Anthropocene · Google Earth · Great acceleration · Landscapes · Palaeoanthropocene

1.1 Google Earth and Landscapes— Introduction Google Earth (GE) is remarkably useful for examining and appreciating phenomena on the face of the Earth. This book aims to demonstrate its value for understanding the landscapes associated with human activities and for appreciating their aesthetics. Many GE images are extraordinarily beautiful. GE was launched in 2005 and is a computer programme that renders a three- dimensional representation of Earth which is based primarily on satellite imagery. It maps the Earth by superimposing satellite images, air photographs, and GIS data onto a 3D globe, allowing its users to see landscapes from a range of angles. It is regularly updated and in its basic form is free for users. It is easily accessed via personal computers. Imagery resolution ranges from 15 cm to 15 m. It provides a distance measuring tool. GE provides near-global coverage, so that it is immensely important for determining global distributions of particular

phenomena (Goudie 2020; Traganos et al. 2018), including miscellaneous desert landforms (Goudie 2022). GE (https://www.google.co.uk/intl/en_uk/earth/) (accessed 7 June 2023) has been much used in landscape studies, for both teaching (see Lisle 2006; Demirci et al. 2013; Tooth 2015) and research (Scheffers et al. 2015). Table 1.1 lists selected studies of the use of GE in the study of particular geomorphological phenomena. A useful site to see GE images of landslides is https://blogs.agu.org/landslideblog/ (accessed 2 May 2023). GE can reveal changes of phenomena over the last four decades through its time lapse function and Google Earth Engine (https://earthengine.google.com/timelapse/) (accessed 7 June 2023) (Gorelick et al. 2017). Among these phenomena are dune migration (Sparavigna 2016), shoreline change (Mao et al. 2021), and river channel migration (Tobón-Marin and Cañón Barriga 2020; Boothroyd et al. 2021). It can also be used to show changes that have occurred in various human driving forces, including irrigation (Deines et al. 2019) and land cover changes that may influence land degradation (Li et al. 2020). There are many examples given in this book of figures that show changes through time. In this volume, the latitudes and longitudes of images are provided, so that they can be relocated by the reader, as are scale bars. These are located in the bottom right corner of all images. Only vertical images are used in this book, but it is also possible to tilt them.

1.2 The Anthropocene This book does not attempt to provide a complete and comprehensive assessment of all aspects of the Anthropocene. It says relatively little, for example, except incidentally, about human impacts on pollution and loss of biodiversity. This in not because these issues are not extraordinarily important,

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 A. Goudie, Landscapes of the Anthropocene with Google Earth, https://doi.org/10.1007/978-3-031-45385-4_1

1

2 Table 1.1  Examples of the use of Google Earth in geomorphological studies

1 Introduction Channel patterns (Colombera and Mountney 2019) Coasts (Scheffers et al. 2012; Warnasuriya et al. 2020) Conglomerate landscapes (Migoń 2020) Debris flows (Xu et al. 2011) Denudation (Cendrero et al. 2022) Dunes (Goudie 2020, 2022; Goudie et al. 2021a, b) Estuaries (Ezcurra et al. 2019) Glacier retreat (Nainwal et al. 2016) Gully erosion (Karydas and Panagos 2020; Reece et al. 2023; Shirani et al. 2023) Lakes (Scheffers and Kelletat 2016) Landslides (Fisher et al. 2012; Rabby and Li 2019; Peng et al. 2021; Sati et al. 2022; Sun et al. 2023) Permafrost landforms (Whalley 2021) River morphology (Henshaw et al. 2020) Rock glaciers (Schmidt et al. 2015; Charbonneau and Smith 2018; Pandey 2019) Salt marshes (Goudie 2013) Soil erosion (Boardman 2016) Thaw slumps (Luo et al. 2019) Tiger bush (Brousse tigrée) (Paron and Goudie 2007) Yardangs (Yang et al. 2023) Wetlands (Amani et al. 2019)

and they have been reviewed elsewhere (see Goudie 2018). It is because the concentration here is upon those aspects of tangible landscapes, especially humanly-made landforms that can be identified on GE images. Secondly, this book has taken a long time perspective. Although the changes that have taken place since the Industrial Revolution and the Great Acceleration (see Sect. 1.4) are enormous and pervasive (Head et al. 2022a,b) in some parts of the world the human impact has been long-continued, and some landscapes reflect this fact (see Sect. 1.3). At the very least it is desirable to place current trends in anthropogenic modifications of landscapes in the context of what has gone before. Thirdly, this book gives example of where human ingenuity and stewardship have successfully halted or reduced landscape degradation. This is what is sometimes seen as the third stage of the Anthropocene (see Chap. 11). The human impact on the environment and the Earth System has been increasing hugely in the last few centuries, and humans are now an enormously powerful ecological and geomorphological force (Brown et al. 2017), not least in East Africa (Odada et al. 2020). As Sherlock (1931), Brown (1970), and Nir (1983) pointed out, humans have had a major impact on landforms and landforming processes. Although people like George Perkins Marsh had championed the role of humans in changing nature in the nineteenth century (Lowenthal 2016), it was only in the early twenty-first century that the Anthropocene concept itself arose (Kolbert et al. 2017; Ellis 2018). The term, though yet to be accepted as an official unit of geologic time, was introduced by Crutzen (2002) as a name for a new epoch in Earth’s history—an epoch when human

activities have, he argued, ‘become so profound and pervasive that they rival, or exceed the great forces of Nature in influencing the functioning of the Earth System’ (Steffen 2010, pp 443). Steffen et al. (2007) identified three stages in the Anthropocene: Stage 1, which lasted from c 1800–1945 they called ‘The Industrial Era’; Stage 2, which extended from 1945 to c 2015, they called ‘The Great Acceleration’; and Stage 3, which may perhaps now be starting (see Chap. 11), is a stage when people have become aware of the extent of the human impact and may thus start stewardship of the Earth System and become more aware of the need for environmental management. Malhi (2017) reviewed some of the evidence for the stages in the development of the human impact on the environment. First, he pointed out that the earliest proposed dates for human modification of Earth System functioning at regional and perhaps global scales are associated with the mass extinction of megafauna coincident with the late Pleistocene expansion of Homo sapiens out of Africa (∼100 kya) and into Australia (∼50 kya), the Americas (∼14 kya), and ultimately numerous islands ranging in size from Madagascar and Japan downwards. He also suggested that a more frequently proposed candidate for the start of the Anthropocene is the onset of agriculture from ∼10 kya. This was, as he said, a global event, with multiple independent origins of farming in Africa, Eurasia, the Americas, and New Guinea, and it increased in spread and intensity throughout the subsequent 10,000 years, with bursts of intensification associated with the development of urban civilisations. A third candidate is around 2 kya, marked by the occurrence of some well-organised societies (Roman Europe, Han China, the middle kingdoms in India, Olmec

1.3  The Palaeoanthropocene

Mexico, pre-Chavin Peru) substantially clearing and altering landscapes at a regional scale and mining for heavy metals, thereby leaving a distinct stratigraphic record of altered anthropogenic soils. Fourth, another late Holocene date that has been proposed is around the sixteenth century. This marks the European invasion and colonisation of the Americas, which had hitherto hosted an isolated and independent experiment in human civilisation.

1.3 The Palaeoanthropocene Indeed, a large group of scientists argue that the Anthropocene has a long history, with early humans causing major environmental changes through such processes as the use of fire and the hunting of wild animals (e.g. Ruddiman 2003; Butler 2018). Indeed, one of the great debates surrounding the Anthropocene is when it started and whether it should be regarded as a formal stratigraphic unit with the same rank as the Holocene (Rull 2013; Edgeworth et al. 2015; Zalasiewicz et al. 2015). Walker et al. (2015), for example, considered the possibility that the Anthropocene might become a subdivision of the Holocene rather than an epoch in its own right. On the other hand, some scientists even argue that the Anthropocene should replace the Holocene, which would become downgraded and reclassified as the final stage of the Pleistocene (Lewis and Maslin 2015). Conversely, there are some who believe that the Anthropocene started with the Industrial Revolution and that 1800 AD is a logical start date for the new epoch (Steffen et al. 2011; Zalasiewicz et al. 2011). At the other extreme, there are those, including archaeologists (Balter 2010; Stephens et al. 2019), who believe that major and widespread human impacts go back considerably further and have drawn attention to their deep history (Ellis et al. 2013a, b; Braje and Erlandson 2014; Braje et al. 2014). This case was made powerfully by Ruddiman et al. (2015, p. 38) who argued ‘Does it really make sense to define the start of a human-dominated era millennia after most forests in arable regions had been cut for agriculture, most rice paddies had been irrigated, and CO2 and CH4 concentrations had been rising because of agricultural and industrial emissions? And does it make sense to choose a time almost a century after most of Earth’s prairie and steppe grasslands had been plowed and planted? Together, forest cutting and grassland conversion are by far the two largest spatial transformations of Earth’s surface in human history. From this viewpoint, the “stratigraphically optimal” choice of 1945 as the start of the Anthropocene does not qualify as “environmentally optimal.”’Ellis (2021) provides a good analysis of the consequences of land use changes over the last 12,000 years and the development of what are termed ‘anthromes’.

3

In New Zealand, Fuller et al. (2015, pp 266–267) found that the nature and timing of human impacts on that country’s river catchments were highly variable between regions and catchments, making any attempt at formally defining the Anthropocene problematic because there is no ubiquitous, synchronous marker that marks the start of the Anthropocene: In catchments draining the Southern Alps, natural processes are far more significant in determining erosion, sedimentation, and river activity. The clearest evidence for Polynesian impact is found in Northland’s catchments in the form of increased floodplain sedimentation. Here, the start of the Anthropocene could be considered to equate with Māori occupation c. 1280 AD, with further augmentation associated with European settlement in the 1800s and 1900s. Farther east, in the East Coast Region of the North Island, the start of the Anthropocene could be taken as c. 1920 when European clearance of indigenous vegetation in the Waipaoa and Waiapu catchments exposed a highly erodible terrain to a range of erosion processes, which resulted in erosion rates exceeding by an order of magnitude those estimated at the end of the Last Glacial Maximum. Each catchment and region must be recognised as unique in its response to human disturbance. New Zealand challenges the notion that the Anthropocene can be defined simply by a critical regime change in which human impact becomes the dominant controlling factor in the environment and overwhelms the forces of nature. New Zealand’s highly active tectonic and climatic regime largely mitigates against Mankind becoming the dominant factor controlling river activity and alluvial sedimentation in most of its naturally dynamic catchments. The exception is Northland and the East Coast Region, where a regime change has been identified by these systems having been overwhelmed by sediment generated as a result of human impact resulting in rapid valley-floor sedimentation.

For these sorts of reasons, Foley et al. (2013) proposed the term ‘Palaeoanthropocene’ for the period between the first signs of human impact way back in the Pleistocene and the start of the Industrial Revolution. In a broadly similar vein, Glikson (2013) said that the Anthropocene could be subdivided into three phases. He regarded the discovery of ignition of fire as a turning point in biological evolution and termed it the ‘Early Anthropocene’. The onset of the Neolithic, he referred to as the ‘Middle Anthropocene’, while the initiation of the industrial age since about 1750 AD he referred to as the ‘Late Anthropocene’. Continuing this long-term perspective, Smith and Zeder (2013) argued that the Anthropocene started at the boundary between the Holocene and the Pleistocene around 10,000 years ago, with the first domestication of plants and animals and the development of agricultural economies. Ruddiman (2013, 2014), on the other hand, argued that early deforestation and agriculture caused large greenhouse gas emissions slightly later, but nevertheless quite early in the Holocene. Certini and Scalenghe (2011) preferred to put the lower boundary at around 2000 years ago when the Greek and Roman civilisations flourished.

4

Arguments about the timing of the Anthropocene continue. The question is asked whether the Anthropocene should be defined as a formal epoch or as an event (Bauer et al. 2021; Swindles et al. 2023). Edgeworth et al. (2023), for example, propose that the Anthropocene concept would be most useful to science if it continues to be regarded as an informal time unit alongside the Geological Time Scale. They suggested that ‘unlike formally defined epochs, geological events can encompass spatial and temporal heterogeneity and the diverse processes that interact to produce global environmental changes’. They argued that humaninfluenced transformations of the Earth System accumulate, intensify, and compound as the Anthropocene Event unfolds. This, they believed, is different from maintaining that an instantaneous transition from one epoch to another has occurred. They continued ‘The idea that human involvement in Earth System change can be adequately represented by a geological series/epoch with shallow temporal depth and a fixed and precisely defined start date, implying a near-instantaneous and recent shift from a natural to human-dominated world, is manifestly oversimplistic’. In like vein, Gale and Hoare (2012) posited that the worldwide diachroneity of human impact makes it impossible and unwise to try and postulate the establishment of a single chronological datum for the start of the Anthropocene. Certainly, it is perilous to think that in all places that the human impact has shown a continually

1 Introduction

increasing trajectory, for there are many examples of ravages in one era being followed by phases of restoration, recovery, and stability in another. Trimble (2013) demonstrated this in the context of the land use and land degradation history of the American mid-west, while in South America there is abundant evidence for wholesale landscape change being achieved by civilisations such as the Incas (Londoño 2008) and the Mayans (Dunning and Beach 1994; Beach et al. 2023) and then being substantially obliterated after European settlement. Figure 1.1 shows some Inca terraces of probable fifteenth century AD date at Pisac in the Sacred Valley of Peru. Figure 1.2 shows the famous Quilmes ruins in the Calchaquí Valleys of Tucumán Province in Argentina. The site was the largest pre-Columbian settlement in that country, occupying about 30 hectares. It probably dates back to ca 850 AD. There are probably many sites waiting to be discovered, especially in areas now covered in rainforest, for there is abundant evidence of anthropogenic soils (Amazonian Dark Earths) and various structures (Walker et al. 2023) over huge areas (de Souza et al. 2018). Undoubtedly, the human impact has developed through time, but of especial note are the early effects of fire, extinctions, and deforestation on geomorphological processes and landscapes. The extinction of great herbivores (e.g. mammoths, mastodons, and giant ground sloths) by early hunters could have had geomorphological ramifications (Haynes 2012)

Fig. 1.1  Google Earth image of Pisac Inca terraces, Peru, dating from the fifteenth century. Scale bar is 200 m. Location: 13° 25′ 2.64ʺ S, 71° 50′ 44.32ʺ W

1.3  The Palaeoanthropocene

5

Fig. 1.2  Google Earth image of Quilmes ruins, Argentina, dating back to c 850 AD. Scale bar is 200 m. Location: 26° 27′ 51.71ʺ S, 66° 2′ 16.17ʺ W

because of their role as earth movers and because of their profound effects on vegetation (Malhi et al. 2016). Even the early manufacture of stone tools could have an environmental impact at the landscape scale (Foley and Lahr 2015), and bell pits associated with the mining of chert for tools in Egypt can date back to the Palaeolithic (Vermeersch et al. 1990). Figure 1.3 shows the craters of a Neolithic flint mine complex in eastern England. Such features occur elsewhere in Britain and in Europe (Baczkowski 2014). In addition, there are many examples of constructed and excavated landforms which date back to antiquity (see Sect. 3.2). In some places, more landscape change may have been achieved during pre-historic times than has been achieved by humans since. For instance, in many parts of the Mediterranean Basin and the Middle East, including Israel (Ackermann et al. 2017), huge tracts of land are characterised by ancient terraces, quarries, check dams, rainwater harvesting structures, and the like. In Baluchistan (Pakistan) there are numerous gabarbands—structures to trap water and sediment—probably dating back to c 5000 years ago (Raikes 1964; Harvey and Flam 1993), while in the Mayan Lowlands of Central America there are raised fields, drainage channels, reservoirs, and other structures that were produced in the ‘Mayacene’ (Beach et al. 2015, 2023), many of which are now being revealed by LIDAR studies (Šprajc et al. 2021). Raised fields from pre-conquest times, and developed at least in part to provide drainage for wetland soil areas, are indeed

still a major feature of large tracts of Amazonia and the Andes (Denevan 2001). Figure 1.4 shows examples with varied morphologies from just northwest (top) and southwest (bottom) of Lake Titicaca in Peru. Figure 1.5 shows some stone terrace walls that were built in valleys in the Negev Desert. Many thousands of them exist (Ore and Bruins 2012). Such terracing dates back to the Neolithic and Chalcolithic, but it was also practised from the Bronze Age through to Byzantine times (Bruins 2012). Figure 1.6 reveals some check dams on small ephemeral wadis in northern Tunisia. They hold back sediment and water and so are advantageous for farming. Substantial changes in land cover in Europe took place in antiquity (Kaplan et al. 2009), and there is increasing evidence to suggest that silty valley fills, many of them dating back to the Bronze and Iron Ages, resulted from accelerated slope erosion produced by the activities of early farmers (Bell 1982). Macklin et al. (2014) used the term ‘Anthropocene Alluvium’ to describe floodplain sediments that have been generated by human activities at different times in the Holocene in Britain (e.g. Foster et al. 2009). Among the formative events that have been identified are: initial Mesolithic and Neolithic woodland clearance; agricultural intensification and sedentarisation in the late Bronze Age; the employment of the iron plough from the early Iron Age onwards; settlement by the Vikings; and

6

1 Introduction

Fig. 1.3  Google Earth image of bell pits left by Neolithic flint mining at Grime’s Graves, Norfolk, England. There are in all c 430 pits, and they were dug c 4600 years ago. They are the remains of shafts dug into the chalk to reach seams of flint. The largest shafts are more than 14 m deep and 12 m in diameter at the surface. Scale bar is 100 m. Location: 52° 28′ 32.27ʺ N, 0° 40′ 30.22ʺ E

the introduction of sheep farming. Sedimentation rates on British floodplains appear to have accelerated markedly in the last thousand or so years (Macklin et al. 2010), and this can be related to the agricultural revolution of medieval times. Likewise, in mainland Europe there have been a number of comparable studies of the history of erosion in the Holocene (Dusar et al. 2011; Notebaert and Verstraeten 2010), of accelerated sedimentation in river basins (Verstraeten et al. 2017), of phases of colluvium accumulation (Henkner et al. 2017; Kaiser et al. 2021), and of sand dune reactivation (Kiss et al. 2012) (see Sect. 10.3.2).

1.4 The Great Acceleration To stress the potency of some early human activities is in no way to imply that the twentieth century was not a time of extraordinary change (McNeill 2000; McNeill and Engelke 2016; Head et al. 2022a, b). Earth’s human population swelled from 1.5 to 6 billion, its economy increased 15-fold, its energy use thirteen- to 14-fold, freshwater use nine-fold, and the irrigated area five-fold. In the ten thousands of years or so from the dawn of agriculture to 1900, McNeill (2003) calculated that humans only used about two-thirds as much energy (most of it from biomass) that they used in the twentieth century. Indeed, he argued that

humans used more energy resources in the twentieth century than in all preceding human history put together. In addition he suggested more fish were caught in the seas and oceans in the twentieth century than in all previous centuries, and that the forest and woodland area shrank by about 20%, accounting for perhaps half the net deforestation in world history (Fig. 1.7). Humans have appropriated a large amount of the world’s biomass for their own use, and Smil (2011) has estimated that through harvesting, deforestation, and conversion of grasslands and wetlands, humans have reduced the stock of global terrestrial plant mass by as much as 45% in the last 2000 years, with a third of this being achieved in the twentieth century. Syvitski et al. (2020) noted the huge expansion in energy use since c 1950. Waters et al. (2016) also addressed this topic and highlighted the rapid development in the use of artificial materials. For example, the manufacture of plastics, which were initially developed in the early years of the twentieth century, rapidly grew from the 1950s. Between 1950 and 2017, 9.2 billion tonnes of plastic are estimated to have been made, with annual production growing to around 380 Tg by 2015 (Geyer et al. 2017) and 400 Tg in 2020, with all the consequent pollution problems with which we are now very familiar. Likewise, concrete, which the Romans invented, has become the primary building material since the Second World War. The period from

1.4  The Great Acceleration

7

Fig. 1.4  Pre-historic raised fields. Top: Google Earth image of raised fields north west of Lake Titicaca in Peru. Scale bar is 200 m. Location: 15° 22′ 13.27ʺ S, 69° 54′ 27.19ʺ W. Bottom: ladder and platform fields near Pomata, which lies to the south west of Lake Titicaca. Scale bar is 200 m. Location: 16° 20′ 0.40ʺ S 69° 18′ 33.25ʺ W

8

1 Introduction

Fig. 1.5  Google Earth image of terraced wadi channels in the Negev Desert, Israel. Some may date back to the Bronze Age. Scale bar is 500 m. Location: 30° 46′ 3.75ʺ N, 34° 42′ 50.10ʺ E

Fig. 1.6  Google Earth image of Tunisian check dams along stream bottoms. Scale bar is 300 m. Location: 34° 7′ 59.02ʺ N, 9° 36′ 58.60ʺ E

References

9

Fig. 1.7  Logs caused by forestry activities awaiting shipment on Gabriola Island, British Columbia, Canada. Scale bar is 100 m. Location: 49° 9′ 12.65ʺ N, 123° 51′ 10.19ʺ W

1995 to 2015 accounts for more than half of the 500,000 Tg of concrete ever produced. This has required earth moving on an unparalleled scale (Cooper et al. 2018), and Waters and Zalasiewicz (2018) have argued that concrete is a prominent marker of the Anthropocene. There may be a range of stratigraphic markers (Head et al. 2022b, p. 1185) of change since the 1950s, including ‘signals generated by the influx into sedimentary successions worldwide of fly ash and black carbon (soot) and many novel entities including plastics, persistent organic pollutants, and artificial radionuclides; global carbon and nitrogen isotope anomalies as a result of hydrocarbon burning and nitrogen production respectively; and a wide range of correlatable bio-events mostly linked to the introduction of non-native species’. Various sites have been cored and dated (see Prillaman 2023). Waters et al. (2023, p. 1) also identified an extensive range of proxies, documenting profound human modification of the Earth System at around the mid-twentieth-century interval. They believed that airborne signals (e.g. radioisotopes, fly ash, stable carbon, and nitrogen isotopes) provide the most widespread and near-isochronous proxies, applicable across most environments. Additional means of correlation that they suggested include the appearance of microplastics (see also Rangel-Buitrago and Neal 2023) and persistent organic pollutants and shifts in heavy metal concentrations and lead isotope ratios. Also, changes

in palaeontological remains of microfossils and some macrofossils of both plants and animals in marine, estuarine, and lake settings reflect both environmental changes and biological introductions (see Williams et al. 2022).

References Ackermann O, Maeir AM, Frumin SS, Svoray T, Weiss E, Zhevelev HM, Horwitz LK (2017) The paleo-anthropocene and the genesis of the current landscape of Israel. J Landsc Ecol 10(3):109–140 Amani M, Mahdavi S, Afshar M, Brisco B, Huang W, Mohammad Javad Mirzadeh S, White L, Banks S, Montgomery J, Hopkinson (2019) Canadian wetland inventory using Google Earth Engine: the first map and preliminary results. Remote Sens 11(7). https:// doi.org/10.3390/rs11070842 Balter M (2010) The tangled roots of agriculture. Science 327:404–406 Bauer AM, Edgeworth M, Edwatds LE, Ellis EC, Gibbard P, Merritts DJ (2021) Anthropocene: event or epoch? Nature 597. https://doi. org/10.1038/d41586-021-02448-z Baczkowski J (2014) Learning by experience: the flint mines of Southern England and their continental origins. Oxford J Archaeol 33(2):135–153 Beach T, Luzzadder-Beach S, Cook D, Dunning N, Kennett DJ, Krause S, Terry R, Trein D, Valdez F (2015) Ancient Maya impacts on the Earth’s surface: an early anthropocene analog? Quat Sci Rev 124:1–30 Beach T, Luzzadder-Beach S, Cook D, Turner BL (2023) Progress in physical geography special issue: physical geography in the Maya Lowlands. Progr Phys Geogr:03091333231162688

10 Bell ML (1982) The effect of land-use and climate on valley sedimentation. In: Harding AF (ed) Climatic change in later prehistory. Edinburgh University Press, Edinburgh, pp 127–142 Boardman J (2016) The value of Google Earth™ for erosion mapping. CATENA 143:123–127 Boothroyd RJ, Williams RD, Hoey TB, Barrett B, Prasojo OA (2021) Applications of Google Earth Engine in fluvial geomorphology for detecting river channel change. Wiley Interdis Rev: Water 8(1):e21496 Braje TJ, Erlandson JM (2014) Looking forward, looking back: humans, anthropogenic change, and the Anthropocene. Anthropocene 4:116–121 Braje T, Erlandson J, Aikens CM, Beach T, Fitzpatrick S, Gonzalez S, Zeder MA (2014) An Anthropocene without Archaeology—should we care? SAA Archaeol Rec 14:26–29 Brown EH (1970) Man shapes the earth. Geogr J 136(1):74–85 Brown AG, Tooth S, Bullard JE, Thomas DS, Chiverrell RC, Plater AJ, Murton J, Thorndycraft VR, Tarolli P, Rose J, Wainwright J (2017) The geomorphology of the Anthropocene: emergence, status and implications. Earth Surf Proc Landf 42(1):71–90 Bruins HJ (2012) Ancient desert agriculture in the Negev and climatezone boundary changes during average, wet and drought years. J Arid Environ 86:28–42 Butler DR (2018) Zoogeomorphology in the Anthropocene. Geomorphology 303:146–154 Cendrero A et al (2022) Denudation and geomorphic change in the Anthropocene; a global overview. Earth Sci Rev 233:104186 Certini G, Scalenghe R (2011) Anthropogenic soils are the golden spikes for the Anthropocene. Holocene 21:1269–1274 Charbonneau AA, Smith DJ (2018) An inventory of rock glaciers in the central British Columbia coast mountains, Canada, from high resolution Google Earth imagery. Arc Antarc Alp Res s 50(1):e1489026 Colombera L, Mountney NP (2019) The lithofacies organization of fluvial channel deposits: a meta-analysis of modern rivers. Sed Geol 383:16–40 Cooper AH, Brown TJ, Price SJ, Ford JR, Waters CN (2018). Humans are the most significant global geomorphological driving force of the 21st century. Anthrop Rev:2053019618800234 Crutzen PJ (2002) Geology of mankind. Nature 415:23 De Souza JG et al (2018) Pre-Columbian earth-builders settled along the entire southern rim of the Amazon. Nat Commun 9(1):1125 Deines JM, Kendall AD, Crowley MA, Rapp J, Cardille JA, Hyndman DW (2019) Mapping three decades of annual irrigation across the US High Plains Aquifer using Landsat and Google Earth Engine. Remote Sens Environ 233:111400 Demirci A, Karaburun A, Kılar H (2013) Using Google Earth as an educational tool in secondary school geography lessons. Int Res Geogr Environ Ed 22(4):277–290 Denevan WM (2001) Cultivated landscapes of native Amazonia and the Andes. Oxford Univ Press, Oxford, p 396 Dunning NP, Beach T (1994) Soil erosion, slope management, and ancient terracing in the Maya lowlands. Lat Am Antiquity 5:51–69 Dusar B, Verstraeten G, Notebaert B, Bakker J (2011) Holocene environmental change and its impact on sediment dynamics in the Eastern Mediterranean. Earth Sci Rev 108:137–157 Edgeworth M, deB Richter D, Waters C, Haff P, Neal C, Price SJ (2015). Diachronous beginnings of the Anthropocene: the lower bounding surface of anthropogenic deposits. Anthrop Rev 2:33–58 Edgeworth M, Gibbard P, Walker M, Merritts D, Finney S, Maslin M (2023) The stratigraphic basis of the Anthropocene event. Quat Sci Adv 13:100088 Ellis EC (2018) Anthropocene: a very short introduction. Oxford University Press, Oxford, p 208 Ellis EC (2021) Land use and ecological change: a 12,000-year history. Ann Rev Environ Resourc 46:1–33

1 Introduction Ellis EC, Kaplan JO, Fuller DQ, Vavrus S, Goldewijk KK, Verburg PH (2013a) Used planet: a global history. Proc Nat Ac Sci 110:7978–7985 Ellis EC, Fuller DQ, Kaplan JO, Lutters, WG (2013b). Dating the Anthropocene: towards an empirical global history of human transformation of the terrestrial biosphere. Elementa. https://doi. org/10.12952/journal.elementa.000018 Ezcurra E et al (2019) Natural experiment reveals the impact of hydroelectric dams on the estuaries of tropical rivers. Sci Adv 5(3):eaau9875 Fisher GB, Amos CB, Bookhagen B, Burbank DW, Godard V, Whitmeyer SJ (2012) Channel widths, landslides, faults, and beyond: the new world order of high-spatial resolution Google Earth imagery in the study of earth surface processes. Geol Soc Am Special Papers 492:1–22 Foley RA, Lahr MM (2015) Lithic landscapes: early human impact from stone tool production on the central Saharan environment. PLoS ONE 10(3):e0116482 Foley SF et al (2013) The Palaeoanthropocene-The beginnings of anthropogenic environmental change. Anthropocene 3:83–88 Foster GC, Chiverrell RC, Thomas GSP, Marshall P, Hamilton D (2009) Fluvial development and the sediment regime of the lower Calder, Ribble catchment, northwest England. CATENA 77(2):81–95 Fuller IC, Macklin MG, Richardson JM (2015) The Geography of the Anthropocene in New Zealand: differential river catchment response to human impact. Geogr Res 53(3):255–269 Gale SJ, Hoare PG (2012) The stratigraphic status of the Anthropocene. Holocene 22:1491–1494 Geyer R, Jambeck JR, Law KR (2017) Production, use, and fate of all plastics ever made. Sci Adv 3(7). https://doi.org/10.1126/ sciadv.1700782 Glikson A (2013) Fire and human evolution: the deep-time blueprints of the Anthropocene. Anthropocene 3:89–92 Gorelick N, Hancher M, Dixon M, Ilyushchenko S, Thau D, Moore R (2017) Google Earth Engine: planetary-scale geospatial analysis for everyone. Remote Sens Environ 202:18–27 Goudie AS (2013) Arid and semi-arid geomorphology. Cambridge University Press, Cambridge, p 454 Goudie A S (2018) The human impact on the natural environment. Wiley Blackwell, Oxford, p 458 Goudie AS (2020) Global barchans: a distributional analysis. Aeol Res 44:100591 Goudie AS (2022) Desert landscapes of the world with Google Earth. Springer, Cham, p 271 Goudie AS, Goudie AM, Viles HA (2021a) The distribution and nature of star dunes: a global analysis. Aeol Res 50:100685 Goudie AS, Goudie AM, Viles HA (2021b) Dome dunes: Distribution and morphology. Aeol Res 51. https://doi.org/10.1016/j. aeolia.2021.100713 Harvey MD, Flam L (1993) Prehistoric soil and water detention structures (gabarbands) at Phang, Sindh Kohistan, Pakistan: an adaptation to environmental change? Geoarchaeology 8(2):109–126 Haynes G (2012) Elephants (and extinct relatives) as earth-movers and ecosystem engineers. Geomorphology 157:99–107 Head MJ et al (2022a) The great acceleration is real and provides a quantitative basis for the proposed Anthropocene Series/Epoch. Episodes 45(4):359–376 Head MJ et al (2022b) The proposed Anthropocene Epoch/Series is underpinned by an extensive array of mid-20th century stratigraphic event signals. J Quat Sci 37(7):1181–1187 Henkner J et al (2017) Archaeopedology and chronostratigraphy of colluvial deposits as a proxy for regional land use history (Baar, southwest Germany). CATENA 155:93–113 Henshaw AJ, Sekarsari PW, Zolezzi G, Gurnell AM (2020) Google Earth as a data source for investigating river forms and processes: discriminating river types using form-based process indicators. Earth Surf Proc Landf 45(2):331–344

References Kaiser K et al (2021) Colluvial sediments originating from past land-use activities in the Erzgebirge Mountains, Central Europe: occurrence, properties, and historic environmental implications. Archaeol Anthropol Sci 13:1–26 Kaplan JO, Krumhardt KM, Zimmermann N (2009) The prehistoric and preindustrial deforestation of Europe. Quat Sci Rev 28:3016–3034 Karydas C, Panagos P (2020) Towards an assessment of the ephemeral gully erosion potential in Greece using Google Earth. Water 12(2):603 Kiss T, Sipos G, Mauz B, Mezösi G (2012) Holocene aeolian sand mobilization, vegetation history and human impact on the stabilized sand dune area of the southern Nyírség, Hungary. Quat Res 78:492–501 Kolbert E, Wilson EO, Lovejoy TE (eds) (2017) Living in the Anthropocene: Earth in the age of humans. Smithsonian Institution, Washington DC, p 208 Lewis SL, Maslin, MA (2015) Defining the Anthropocene. Nature 519:171–180 Li Q, Qiu C, Ma L, Schmitt M, Zhu XX (2020) Mapping the land cover of Africa at 10 m resolution from multi-source remote sensing data with Google Earth Engine. Remote Sens 14(4). https://doi. org/10.3390/rs12040602 Lisle RJ (2006) Google Earth: a new geological resource. Geol Today 22(1):29–32 Londoño AC (2008) Pattern and rate of erosion inferred from Inca agricultural terraces in arid southern Peru. Geomorphology 99:13–25 Lowenthal D (2016) Origins of anthropocene awareness. Anthrop Rev 3(1):52–63 Luo J, Niu F, Lin Z, Liu M, Yin G (2019) Recent acceleration of thaw slumping in permafrost terrain of Qinghai-Tibet Plateau: an example from the Beiluhe region. Geomorphology 341:79–85 Macklin MG, Jones AF, Lewin J (2010) River response to rapid Holocene environmental change: evidence and explanation in British catchments. Quat Sci Rev 29:1555–1576 Macklin MG, Lewin J, Jones AF (2014) Anthropogenic alluvium: an evidence-based meta-analysis for the UK Holocene. Anthropocene 6:26–38 Malhi Y (2017) The concept of the Anthropocene. Ann Rev Environ Resourc 42:77–104 Malhi Y, Doughty CE, Galetti M, Smith FA, Svenning JC, Terborgh JW (2016) Megafauna and ecosystem function from the Pleistocene to the Anthropocene. Proc Nat Acad Sci 113(4):838–846 Mao Y, Harris DL, Xie Z, Phinn S (2021) Efficient measurement of large-scale decadal shoreline change with increased accuracy in tide-dominated coastal environments with Google Earth Engine. J Photogrammetry Remote Sens 181:385–399 McNeill JR (2000) Something new under the sun. An environmental history of the twentieth century world. Allen Lane, the Penguin Press, London, p 419 McNeill JR (2003) Resource exploitation and over-exploitation: a look at the 20th century. In: Benzing TS, Herrmann B (eds) Exploitation and overexploitation in societies past and present. LIT Verlag, Münster, pp 1–60 McNeill JR, Engelke P (2016) The great acceleration. Harvard University Press, Cambrigde, Massachusetts, p 288 Migoń P (2020) Geomorphology of conglomerate terrains–global overview. Earth Sci Rev 208:103302 Nainwal HC, Banerjee A, Shankar R, Semwal P, Sharma T (2016) Shrinkage of Satopanth and Bhagirath Kharak glaciers, India, from 1936 to 2013. Ann Glaciol 57:131–139 Nir D (1983) Man, a geomorphological agent. Keter, Jerusalem, p 165 Notebaert B, Verstraeten G (2010) Sensitivity of West and Central European river systems to environmental changes during the Holocene: a review. Earth Sci Rev 103:163–182 Odada EO, Olago DO, Olaka LA (2020) An East African perspective of the Anthropocene. Sci Afr 10:e00553

11 Ore G, Bruins HJ (2012) Design features of ancient agricultural terrace walls in the Negev Desert: human-made geodiversity. Land Degrad Develop 23:409–418 Pandey P (2019) Inventory of rock glaciers in Himachal Himalaya, India using high-resolution Google Earth imagery. Geomorphology 340:103–115 Paron P, Goudie AS (2007) Preliminary results about mapping and geomorphological correlation of tiger bush (Brousse tigrée) in Somalia, from a remote sensing and GIS analysis perspective. In: Goudie AS, Kalvoda J (eds) Geomorphological variations. Nakladatelství P3K, Prague, pp 37–86 Peng D, Yueren X, Qinjian T, Wenqiao L (2021) Using Google Earth images to extract dense landslides induced by historical earthquakes at the southwest of Ordos, China. Front Earth Sci 8:633342 Prillaman M (2023) Are we in the Anthropocene? Geologists could define new epoch for Earth. Nature 613(7942):14–15 Rabby YW, Li Y (2019) An integrated approach to map landslides in Chittagong Hilly areas, Bangladesh, using Google Earth and field mapping. Landslides 16(3):633–645 Raikes R (1964) The ancient gabarbands of Baluchistan. East and West 15(1/2):26–35 Rangel-Buitrago N, Neal WJ (2023) A geological perspective of plastic pollution. Sci Total Environ 16:164867 Reece DA, Lory JA, Haithcoat TL, Gelder BK, Cruse R (2023) Using Google Earth imagery to target sssessments of ephemeral gully erosion. J Am Soc Agric Biol Eng 66(1):155–166 Ruddiman WF (2003) The anthropogenic greenhouse era began thousands of years ago. Clim Change 61:261–293 Ruddiman WF (2013) The anthropocene. Ann Rev Earth Planet Sci 41:45–68 Ruddiman WF (2014) Earth transformed. W.H. Freeman and Company, New York, p 400 Ruddiman WF, Ellis EC, Kaplan JO, Fuller DQ (2015) Defining the epoch we live in. Science 348:38–39 Rull V (2013) A futurist perspective on the Anthropocene. Holocene 23:1198–1201 Sati SP et al (2022) Mountain highway stability threading on the fragile terrain of upper Ganga catchment (Uttarakhand Himalaya), India. J Mountain Sci 19(12):3407–3425 Scheffers AM, Kelletat DH (2016) Lakes of the world with Google Earth: understanding our environment. Springer, Dordrecht, p 306 Scheffers AM, Scheffers SR, Kelletat D (2012) The coastlines of the world with Google Earth: understanding our environment. Springer, Dordrecht, p 305 Scheffers AM, May SM, Kelletat DH (2015) Landforms of the world with Google Earth: understanding our environment. Springer, Dordrecht, p 401 Schmid MO, Baral P, Gruber S, Shahi S, Shrestha T, Stumm D, Wester P (2015) Assessment of permafrost distribution maps in the Hindu Kush Himalayan region using rock glaciers mapped in Google Earth. Cryosphere 9(6):2089–2099 Sherlock RL (1931) Man’s influence on the Earth. Butterworth, London, p 253 Shirani K, Peyrowan, Shadfar S (2023) Gully erosion mapping based on hydro-geomorphometric factors and geographic information system. Environ Monit Assess 195. https://doi.org/10.1007/ s10661-023-11197-7 Smil V (2011) Harvesting the biosphere: the human impact. Pop Develop Rev 37:613–636 Smith BD, Zeder MA (2013) The onset of the anthropocene. Anthropocene 4:8–13 Sparavigna AC (2016) Analysis of the motion of some Brazilian coastal dunes. Int J Sci 5(1):22–31 Šprajc I, Dunning NP, Štajdohar J, GómezQH, López IC, Marsetič A., Ball JW, Góngora SD, Olguín OQE, Esquivel AF, Kokalj Ž (2021) Ancient Maya watermanagement, agriculture, and society in the area of Chactún, Campeche, Mexico. J Anthropol Archaeol61:101261

12 Steffen W (2010) Observed trends in Earth System behaviour. Wiley Interdiscip Rev: Clim Change 1:428–449 Steffen W, Crutzen PJ, McNeill JR (2007) The Anthropocene: are humans now overwhelming the great forces of nature? Ambio 36:614–621 Steffen W, Grinevald J, Crutzen P, McNeill J (2011) The Anthropocene: conceptual and historical perspectives. Phil Trans Roy Soc 369A:842–867 Stephens L et al (2019) Archaeological assessment reveals Earth’s early transformation through land use. Science 365:897–902 Sun H, Li W, Scaioni M, Fu J, Guo X, Gao J (2023) Influence of spatial heterogeneity on landslide susceptibility in the transboundary area of the Himalayas. Geomorphology 433:108723 Swindles GT, Roland TP, Ruffell (2023) The ‘Anthropocene’is most useful as an informal concept. J Quat Sci. https://doi.org/10.1002/ jqs.3492 Syvitski J et al (2020) Extraordinary human energy consumption and resultant geological impacts beginning around 1950 CE initiated the proposed Anthropocene Epoch. Comm Earth Environ 1(1). https://doi.org/10.1038/s43247-020-00029-y Tobón-Marín A, Cañón Barriga J (2020) Analysis of changes in rivers planforms using Google Earth Engine. Int J Remote Sens 41(22):8654–8681 Tooth S (2015) Google Earth as a resource. Geography 100:51–56 Traganos D, Aggarwal B, Poursanidis D, Topouzelis K, Chrysoulakis N, Reinartz P (2018) Towards global-scale seagrass mapping and monitoring using Sentinel-2 on Google Earth Engine: the case study of the Aegean and Ionian seas. Remote Sens 10(8):1227 Trimble SW (2013) Historical agriculture and soil erosion in the Upper Mississippi valley hill country. CRC Press, Boca Raton, p 290 Vermeersch PM, Paulissen E, Van Peer P (1990) Palaeolithic chert exploitation in the limestone stretch of the Egyptian Nile Valley. Afr Archaeol Rev 8(1):77–102 Verstraeten G, Broothaerts N, Van Loo M, Notebaert B, D’Haen K, Dusar B, De Brue H (2017) Variability in fluvial geomorphic response to anthropogenic disturbance. Geomorphology 294:20–39 Walker M, Gibbard P, Lowe J (2015) Comment on “When did the Anthropocene begin? A mid-twentieth century boundary is stratigraphically optimal” by Jan Zalasiewicz et al. (2015). Quat Int 383:204–207

1 Introduction Walker RS, Ferguson JR, Olmeda A, Hamilton MJ, Elghammer J, Buchanan B (2023) Predicting the geographic distribution of ancient Amazonian archaeological sites with machine learning. Peer J 11:e15137. https://doi.org/10.7717/peerj.15137 Warnasuriya TW, Kumara MP, Gunasekara SS, Gunaalan K, Jayathilaka RM (2020) An improved method to detect shoreline changes in small-scale beaches using Google Earth Pro. Marine Geod 43(6):541–572 Waters CN, Zalasiewicz J (2018) Concrete: the most abundant novel rock type of the anthropocene. In: Elias SA (ed) Encyclopedia of the anthropocene. Elsevier, Amsterdam, pp 75–85 Waters CN et al (2016) The Anthropocene is functionally and stratigraphically distinct from the Holocene. Science 351. https://doi. org/10.1126/science.aad2622 Waters CN, Turner SD, Zalasiewicz J, Head MJ (2023) Candidate sites and other reference sections for the Global boundary Stratotype Section and Point of the Anthropocene series. Anthrop Rev:20530196221136422 Whalley WB (2021) Geomorphological information mapping of debris-covered ice landforms using Google Earth: an example from the Pico de Posets, Spanish Pyrenees. Geomorphology 393:107948 Williams M et al (2022) Planetary-scale change to the biosphere signalled by global species translocations can be used to identify the Anthropocene. Palaeontology 65(4):e12618 Xu LR, Su ZM, Ugai K, Cai F, Yang QQ (2011) Google Earth as a tool in terrain survey of debris flow watershed. Adv Materials Res 261:1563–1566 Yang HA, Weitao YU, Zhongping LA, Shixiu CH, Wenke LI (2023) Extraction of yardang landforms boundary based on multi-spatial resolution Google Earth image and Canny edge algorithm. Bull Surveying Mapping 25(5):175–179 Zalasiewicz J, Williams M, Haywood A, Ellis M (2011) The Anthropocene: a new epoch of geological time? Phil Trans Roy Soc 369A:835–841 Zalasiewicz J, Waters CN, Williams M, Barnosky AD, Cearreta A, Crutzen P, Oreskes N (2015) When did the Anthropocene begin? A mid-twentieth century boundary level is stratigraphically optimal. Quat Int 383:196

2

Driving Forces

Abstract

This chapter explores the various driving forces that explain the human impact on the environment during the Anthropocene. These are population growth, the introduction of farming, deforestation and other land cover changes, urbanisation, mining, the role of energy sources, tourism, and anthropogenic climate change.

Keywords

Agriculture · Fire · Deforestation · Urbanisation · Mining · Energy · Tourism · Climate change

2.1 Introduction The twentieth century was a time of extraordinary technological and social change (McNeill and Engelke 2016). Rapid population growth, extensive deforestation, expansion of agriculture and pastoralism, and the emission of pollutants into the atmosphere went on apace. Mining caused major environmental changes (see, for example, Dethier et al. 2018) (see Sects. 2.7, 4.8.5, 8.5, and 9.8.4). Energy resources were developed at an ever-increasing rate, giving humans enormous power to transform the geomorphological environment, not least in China, where economic growth was spectacular. Increasing amounts of energy are being used, and new sources, including renewables, have been sought (see Sect. 2.8). To take one example, hydropower schemes, which require the construction of major dams (Zarfl et al. 2015) and which have major consequences for river flow and sediment trapping (see Sect. 4.2), have expanded in distribution and size. Moran et al. (2018) note that an estimated 3700 dams that produce more than one megawatt are either planned or under construction primarily in developing countries. Particular concern has been expressed about the potential impacts of

burgeoning dam construction on river connectivity across the enormous Amazon basin, especially on its floodplains and the oceanic waters into which it flows (Latrubesse et al. 2017; Anderson et al. 2018). Figure 2.1 shows two major dams built in the last seven decades: the Tarbela on the Indus and the Grand Ethiopian Renaissance Dam on the Nile. An important point that one can make here is that one driving force—dam construction—can have a multitude of impacts (Fig. 2.2). Compounding the effects of rapidly expanding populations (see Sect. 2.2) has been a general increase in per capita consumption and environmental impact. We have also transformed the biological environment, by causing extinctions, and now of all the mammals on Earth only 4% are wild (Bar-on et al. 2018). It is also important to remember that we have entered the Fourth Industrial Revolution, and that Artificial Intelligence (AI) has a multitude of potential impacts on future environments, including an impact on carbon budgets (Dhar 2020). On the other hand, with its ability to analyse huge quantities of data, learn from patterns, and make decisions in real time, AI can be employed to improve such things as energy efficiency and to reduce waste.

2.2 Demographical Developments There would be no Anthropocene without humans. In Africa and Eurasia, humans date back several millions of years. However, the Americas and Australia were probably uninhabited until c 15,000 and 50,000 years, respectively. Many islands in Oceania were not settled until much more recently. Some, called ‘neoinhabited’ islands, were discovered and settled just one or two millennia ago (e.g. Madagascar, New Zealand, Hawaii, and the Canaries), and yet others remained unsettled until four or five hundred years ago (e.g. the Azores, Madeira, Galápagos) (Whittaker et al. 2003).

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 A. Goudie, Landscapes of the Anthropocene with Google Earth, https://doi.org/10.1007/978-3-031-45385-4_2

13

14

2  Driving Forces

Fig. 2.1  Google Earth images of large dams. Top: The Tarbela Dam, Pakistan. Scale bar is 2 km. Location: 34° 5′ 9.62ʺ N, 72° 42′ 27.74ʺ E. Bottom: The Grand Ethiopian Renaissance Dam, Ethiopia. Scale bar is 2 km. Location: 11° 12′ 59.53ʺ N, 35° 5′ 12.96ʺ E

At the peak of the Last Glacial Maximum c 20,000 years ago, the population of the Old World was probably a mere 2–8 million (Gautney and Holliday 2015), and by late medieval times the figure had climbed to c 400–500

million. In 1969 the global human population was 3.4 billion. By 2022 it exceeded 8 billion. Likewise, in 1969 the percentage of the global population which was urban amounted to 36.3%, while by 2021 this figure had grown

15

2.3 Farming

Fig. 2.2  Range of impacts on dam and reservoir construction (Modified after Goudie and Viles 2016, Fig. 7.2)

to 56% (over 4 billion people) (https://data.worldbank.org/ indicator/SP.URB.TOTL.IN.ZS) (accessed 7 June 2023). Demographical pressures have been implicated in desertification, and in 1977 the United Nations Conference on Desertification (UNCOD) in Nairobi adopted a Plan of Action to Combat Desertification (PACD). Generally, developed nations have seen a decline in their growth rates in recent decades, though annual growth rates remain above 2% in some developing countries in sub-Saharan Africa, Latin America, and the Middle East. However, in some areas such as Eastern Europe and Japan, mainly due to factors such as low fertility rates, the readily availability of the pill (approved in 1960) and other forms of contraception, and the career ambitions of educated women, rates are decreasing, and Japan’s population began to fall in 2005. By 2100, the global population is expected to exceed about 11 million.

2.3 Farming Farming has shown a great expansion in recent decades. On a global scale, 45% more meat was produced in 2020 compared with 2000, primary crop production was 52% more, sugar cane production was 35% more, and global fisheries and aquaculture were up by c 40% (https://www. fao.org/3/cc2211en/online/cc2211en.html#chapter-2) (accessed 7 June 2023).

One feature of the last few centuries has been the conversion of wetlands to other uses, and in particular to farming (see Sect. 4.11). Fluet-Chouinard et al. (2023) examined global data on inland wetlands—areas inundated or waterlogged for at least one continuous month during the period of record, regardless of surface vegetation— but excluding permanently inundated areas (river channels and lakes), coastal intertidal zones, and near-shore marine wetlands. They estimated that the global area of natural inland wetlands has declined by c 3.4 Mkm2 since 1700. This estimate corresponds to a loss of c 21% of the c 15.8 Mkm2 wetlands estimated to have existed in 1700. They suggested that wetland drainage for upland croplands was the most common cause of loss (61.7% of the total), followed by conversion to flooded rice (18.2%), urban areas (8.0%), forestry (4.7%), wetland cultivation (4.3%), pasture (2.0%), and peat extraction (0.9%). The use of coastal waters for aquaculture is steadily increasing and takes various forms. Figure 2.3 shows fish ponds that have been built in former mangrove swamp areas in Bali, Indonesia. Figure 2.4 is an image of shrimp ponds that have been constructed along the coast of Sonora in Mexico, Fig. 2.5 shows seaweed farming structures from Susan Island in South Korea, while Fig. 2.6 is an illustration of fish farming tanks at Rotten Bay in South Australia. In recent decades increases in agricultural production have partially resulted from a rapid and substantial spread of irrigation across the world. The irrigated area in 1900

16

2  Driving Forces

Fig. 2.3  Google Earth image of Bali Sea aquaculture. M = Mangrove swamp. Scale bar is 1 km. Location: 8° 7′ 46.09ʺ S, 114° 34′ 42.97ʺ E

Fig. 2.4  Google Earth image of Sonora shrimp ponds, Mexico. Scale bar is 8 km. Location: 28° 33′ 43.08ʺ N, 111° 34′ 6.07ʺ W

2.3 Farming

Fig. 2.5  Google Earth image of seaweed farming, Susan Island, South Korea. Scale bar is 500 m. Location: 34° 8′ 32.44ʺ N, 126° 35′ 6.44ʺ E

Fig. 2.6  Google Earth image of Rotten Bay fish farms, South Australia. Scale bar is 100 m. Location: 34° 43′ 44.37ʺ S, 135° 56′ 2.78ʺ E

17

18

amounted to less than 50 Mha. By 2020 the total area amounted to c six times that figure (343 Mha). During the 1950s the irrigated area was increasing at over 4% annually, though this figure has now dropped to only about 1%. China is the top country by total area equipped for irrigation in the world. As of 2020, total area equipped for irrigation in China was 74 Mha accounting for 21.82% of the world’s total area equipped for irrigation. The top 5 countries (the others are India, the USA, Pakistan, and Iran) account for 59.38% of it (https://knoema.com/ atlas/topics/Land-Use/Area/Total-area-equipped-forirrigation?type=maps) (accessed 7 June 2023). Irrigation is a major driver of river salinisation in many parts of the world (Thorslund et al. 2021). Irrigation is often achieved by leading off canals from major rivers (as in Mesopotamia, the Nile Delta (see Fig. 2.7), the Gezira Scheme in Sudan (Fig. 2.8), and in northwest India and Pakistan). Besides transforming landscapes in this way, irrigation has caused a great deal of salinisation and waterlogging. For example, in Touggourt in the Oued Righ valley of the Algerian Sahara, salt has built up over the years as a result of overuse of groundwater, releases of wastewater, and inadequate drainage (Khelifi Touhami et al. 2020). The Oued Righ valley consists of 50 palm groves containing 2 million palm trees, but more than half of the valley’s palm groves have now had to be abandoned.

2  Driving Forces

Daliakopoulos et  al. (2016) suggested that in the Mediterranean region, soil salinisation affects 25% of irrigated agricultural land at a significant level, while Eswar et al. (2021) calculated that nearly 20% of the world’s irrigated lands, spread over 120 countries, are salinised. Enhanced or accelerated salinisation has in turn often led to salt weathering problems, as has been observed at major heritage sites like Babylon in Iraq, Bokhara in central Asia, and Mohenjo-Daro in Pakistan (Goudie and Viles 1997). Figure 2.9 shows an area of irrigation in the Touggurt area of Algeria, where large tracts of formerly irrigated fields have had to be abandoned because of salinisation. Salt weathering has also attacked the foundations of the ksours (fortified villages) of this location (Bencherif 2008). In many parts of the world humans obtain water supplies by pumping from groundwater reservoirs (Wada et al. 2010). Now about 38% of the world’s irrigated areas are groundwater-based, and about 43% of irrigation water is derived from underground aquifers (Siebert et al. 2010). The proportion of total groundwater abstraction used for irrigation varies significantly between countries (https:// www.tandfonline.com/doi/full/10.1080/27678490.2022 .2090867) (accessed 7 June 2023). India, as the largest groundwater user globally, at an estimated 251 km3 per year abstracted, uses 89% of its groundwater abstraction for irrigation. China is relatively less reliant on groundwater, with an estimated 54% of total groundwater abstraction

Fig. 2.7  Google Earth image of towns, villages, and irrigation in the Nile Delta, Egypt. Scale bar is 70 km. Location: 30° 48′ 30.53ʺ N, 31° 15′ 56.24ʺ E

2.3 Farming

19

Fig. 2.8  Google Earth image of Gezira irrigation scheme, Sudan. Scale bar is 2 km. Location: 14° 15′ 48.36ʺ N, 32° 41′ 47.03ʺ E

Fig. 2.9  Google Earth image of salinisation of fields by irrigation at Touggurt, Algeria. Scale bar is 1 km. Location: 32° 57′ 7.63ʺ N, 5° 59′ 54.14ʺ E

20

going into irrigation on average, but with significant geographical disparities, with the North China Plain being more critically reliant on groundwater compared to the southern regions. Other countries, such as Bangladesh, Iran, Mexico, Pakistan, Saudi Arabia, and the USA, are also heavily reliant on groundwater for irrigation, with amounts of groundwater abstraction for irrigation ranging from 71 to 94%. Groundwater is also important as a source of water for municipal consumption. Increasing population levels and the adoption of new exploitation techniques (e.g. the replacement of irrigation methods involving animal or human power by electric and diesel pumps) have increased these problems. Global groundwater abstraction increased from c 312 km3 per year in 1960 to c 959 km3 per year in 2017 (https:// unesdoc.unesco.org/ark:/48223/pf0000380733) (accessed 7 June 2023), and this abstraction exceeded recharge, so that over the same period groundwater reserves became depleted. This had two main effects: reduction in the water table levels and the replacement, in coastal areas, of freshwater by salt water (Barlow and Reichard 2010), a process called salt water intrusion. Environmental consequences of these two phenomena include ground subsidence and soil salinisation. The use of groundwater for irrigation has sometimes been achieved by the traditional technique of qanat (as in large tracts of the Middle East) (Wilkinson 1977) and North Africa and by the much more modern technique of using centre pivots. The qanat systems, also known as foggara in Algeria, khettara in Morocco, falaj in Oman, kārīz in Iran, karez in Afghanistan, and auyoun in Saudi Arabia, consist of an underground aqueduct collecting groundwater from a mother well, sunk into an aquifer, which is often located in an alluvial fan. It is common for them to start below the foothills of mountains, where the water table is closest to the surface. Groundwater infiltrating into the wells is transported by gravity through a gently sloping tunnel to a main canal and distribution point, whence minor ditches then diverge to bring water to the areas being irrigated. In Iran some shafts are 100–120 m deep, and the tunnels may run as far as 40–50 km. However, in some localities, because of the lowering of the water table by modern systems of pumping, they are in decline (Remini et al. 2011). Lines of waste pits and shafts can form dramatic landscape features. One technological breakthrough for the exploitation of groundwater for irrigation was the development of the self-governing windmill. Especially after the 1890s this was used extensively in the Great Plains (Baker 1989). Centre-pivot irrigation is a more modern method for watering crops in which booms rotate around a pivot and crops are watered with sprinklers. It was invented in the 1940s by a Colorado farmer, Frank Zybach, and patented in 1952.

2  Driving Forces

The pivot accesses groundwater which is then pumped up and spread through the booms to which sprinklers are attached. As the booms rotate in a circular pattern, the irrigated fields are generally round. Figure 2.10 shows a large area of centre-pivot systems in northwest Saudi Arabia, while Fig. 2.11 shows similar systems in the far south of Egypt. After being invented in the 1940s, they became very widely used in many arid areas. They consume large amounts of water. The consequent reductions in water levels that are taking place in the High Plains aquifers of the USA from Nebraska to Texas are some of the most serious (Sophocleous 2010; Scanlon et al. 2012) and threaten the long-term viability and sustainability of the area’s irrigated agriculture. Before irrigation development, this system, one of the largest in the world and covering some 450,000 km2, was in a state of dynamic equilibrium, with long-term recharge equal to long-term discharge. Then everything was changed through ‘the perfect triad’ of electricity, the centrifugal pump, and centre-pivot irrigation (Alley and Alley 2017). The groundwater is now effectively being mined, and water levels have declined by 30 to 60 m, particularly in a large tract to the north of Lubbock in Texas. Streams in the area now receive a reduced groundwater input, so that their flows have declined (Kustu et al. 2010) (see Sect. 4.13.1). In southeast Libya, groundwater within the Nubian Sandstone (Cambrian to Upper Cretaceous in age) aquifer has been mined by centre-pivot systems to produce irrigated fields in one of the most arid parts of the Libyan Desert. The water, thought to date back to a pluvial in the Late Pleistocene, is a finite fossil resource. Each field covers 100 ha, and the diameter of the sprinklers is 560 m. Figure 2.12 (top) shows the system as it was in 1992, while Fig. 2.12 (bottom) shows the situation twenty years later. It is clear that there has been a very marked contraction in the area irrigated. The reasons for this are not clear, but there has been a decline in aquifer thickness and water quality (Hamad and Ahweej 2020), and there has also been severe political instability in Libya. In addition, the economics of this project in such a remote region have always been the subject of debate. Another country that is mining groundwater resources very intensively is Saudi Arabia. Aquifer depletion, water quality diminution, and ground subsidence and fissuring have been recorded (Youssef et al. 2014). As in Libya, the aquifers that are being exploited are relicts of a Late Pleistocene pluvial and are receiving very limited recharge under the arid conditions that pertain today. Mazzoni et al. (2018, p.157) have calculated that ‘the majority of the small to mid-size exploitable fossil aquifer systems in the Arabian Peninsula could reach full depletion by 2050 and the total depletion of groundwater resources in all aquifer systems could be reached in ∼60–90 years’.

2.3 Farming

21

Fig. 2.10  Google Earth image of a huge centre-pivot irrigation scheme in northwest Saudi Arabia. Scale bar is 50 km. Location: 30° 9′ 15.00ʺ N, 38° 25′ 53.49ʺ E

Fig. 2.11  Google Earth image of centre-pivot irrigation scheme in southern Egypt. Scale bar is 10 km. Location: 22° 33′ 45.23ʺ N, 28° 32′ 29.38ʺ E

22

2  Driving Forces

Fig. 2.12  Google Earth images of centre-pivot irrigation scheme in Kufrah, Libya, in 1992 (top) and 2022 (bottom). Notice the decline that has taken place. Scale bar is 9 km. Location: 24° 9′ 38.59ʺ N, 23° 26′ 20.08ʺ E

2.4 Fires Humans are known to have used fires since the Palaeolithic, and shifting agriculturalists and pastoralists have employed fire to modify vegetation for millennia. Over large tracts of bush in the interior of Australia, fire scars are clearly evident (Fig. 2.13), and the Maori of New Zealand utilised

fire to transform forest cover prior to European settlement. The frequency and intensity of fires is an important factor in many biomes (Nitschke and Innes 2013), and fires are highly dependent on weather and climate, being more likely to occur in drought years or when there are severe lightning strikes. Wind conditions are also a significant control of fire severity. Fire frequencies have grown substantially

2.4 Fires

23

Fig. 2.13  Google Earth images of fire scars across linear dune country, Yellabinna, South Australia. Top 1990, bottom 2020. Scale bar is 10 km. Location: 20° 22′ 21.34ʺ S, 126° 2′ 37.76ʺ E

in the boreal forests of Russia, Canada, and the USA in recent warming decades (Soja et al. 2007). For the Earth as a whole, Jolly et al. (2015) showed that from 1979 to 2013 there had been a significant increase in the length of

the fire season and in the area burned, and this was confirmed up to 2019 by Tyukavina et al. (2022). On the other hand, at a global scale, remote sensing data showed that the burned area declined by nearly one-quarter between 1998

24

and 2015. Decreases occurred in many tropical savannas because of shifts towards more capital intensive agriculture (Andela et al. 2017). As regards the future the Intergovernmental Panel on Climate Change (2022, p. 270) (https://report.ipcc.ch/ar6/ wg2/IPCC_AR6_WGII_FullReport.pdf) (accessed 7 June 2023) suggested that under a high-emission scenario that increases global temperature 4 °C by 2100, climate change could increase the global burned area by 50–70% and the global mean fire frequency by ~30%. Lower emissions that would limit the global temperature increase to less than 2 °C would increase the global burned area by c 35% and the fire frequency by c 20%. A major causative factor for the recent increase in fire activity (Jones et al. 2020) has been drought intensification associated with climate change. Fires play an important role in such processes as tree removal, slope destabilisation, and permafrost disruption (Chen et al. 2021). Fires also seem to expose land so that wind attack generates enhanced emissions from dust storms (Yu and Ginoux 2022). Figure 2.14 shows the way in which the vegetation cover of an area can be transformed by fire. It shows Paradise in California in 2014 (top) and again in 2022 (bottom) after the great fire of November 2018.

2.5 Deforestation Deforestation is one of the great processes of landscape transformation (Williams 2003) and has many geomorphological consequences (see Sects. 4.13.2 and 9.3). Evidence of human impacts on tropical forests dates back well into pre-history (Scerri et al. 2022; Roberts et al. 2018) but since that time the process has accelerated. On a global basis, Richards (1991, p. 164) calculated that since 1700 about 19% of the world’s forests and woodlands have been removed. Between 2015 and 2020, the rate of deforestation was estimated at 10 Mha per year, down from 16 Mha per year in the 1990s. A recent survey by Estoque et al. (2022, p. 1) has updated the global picture. They show that ‘over the past 60 years (1960–2019), the global forest area has declined by 81.7 Mha (i.e. 10% more than the size of the entire island of Borneo), with forest loss (437.3 Mha) outweighing forest gain (355.6 Mha). With this forest decline and the human population increase (4.68 billion) over the period, the global forest per capita has decreased by over 60%, from 1.4 ha in 1960 to 0.5 ha in 2019. The spatiotemporal pattern of forest change supports the forest transition theory, with forest losses occurring primarily in the lower income countries in the tropics and forest gains in the higher income countries in the extratropics’. In Africa Aleman et al. (2018) estimated a total net loss in forest extent of ~21.7% between AD 1900 and AD 2000.

2  Driving Forces

They found that changes in forest cover were heterogeneous: West and East African forests have been decimated (net loss of ~83.3% in West Africa and ~93.0% in East Africa), but the core Congolese forest extent in Central Africa has increased by ~1.4% on average, with some regions in that region losing and others gaining closed-canopy forests. In Madagascar, Suzzi-Simmons (2023) examined deforestation between 2001 and 2021 and found that the island had lost 4.85 Mha of tree cover since 2000, equivalent to a 25% decrease in tree cover. In West Africa, much deforestation is caused by cocoa cultivation in countries like Ghana and Côte d’Ivoire (Kalischek et al. 2023). In 2023 the World Resources Institute (https:// research.wri.org/gfr/latest-analysis-deforestation-trends) (accessed 2 July 2023) reported that tropical primary forest loss in 2022 totalled 4.1 Mha, that in Brazil, the rate of primary forest loss increased by 15% from 2021 to 2022, with the vast majority of primary forest loss happening in the Amazon. The Democratic Republic of the Congo (DRC) lost over half a million hectares (Mha) in 2022, and Bolivia saw a record-high level of primary forest loss in 2022, with a 32% increase from 2021 levels. For the third year running, Bolivia was third behind only Brazil and the Democratic Republic of the Congo in area of primary forest loss, surpassing Indonesia despite having less than half the amount of primary forest. The great phase of deforestation in central and Western Europe described by Darby (1956, p. 194) as ‘the great heroic period of reclamation’ occurred from c AD 1050 onwards for about 200 years. In particular, the Germans moved eastwards: ‘What the new west meant to young America in the nineteenth century, the new east meant to Germany in the Middle Ages’ (Darby 1956, 196). The landscape of Europe was transformed (Kaplan et al. 2009), just as that of North America, Australia, New Zealand, and South Africa were to be as a result of the European expansions, especially in the nineteenth century. Temperate North America underwent particularly brutal deforestation (Williams 1989) and lost more woodland in 200 years than Europe did in 2000. The first colonialists from Europe found a continent that was wooded from the Atlantic seaboard as far as the Mississippi River. This forest covered c 170 Mha, but today only c 10 Mha remain. From 2000 to 2020, the world experienced a net change of − 101 Mha (− 2.4%) in tree cover. From 2002 to 2021, there was a total of  68.4 Mha  humid primary forest lost globally, making up 16% of its total tree cover loss. In the same time period the total area of humid primary forest decreased globally by 6.7%. However, some areas gained in forest cover. From 2000 to 2020, 131 Mha of tree cover was gained globally, 37.2 Mha in Russia, 17.0 Mha in Canada, 14.0 Mha in the USA, 8.06 Mha in Brazil, and 6.69 Mha in China (https://www.globalforestwatch.org/dashboards/global) (accessed 7 June 2023).

2.5 Deforestation

25

Fig. 2.14  Google Earth images of Paradise, California, USA, before the fire of 2018 (top) and after the fire (bottom). Note the marked change in tree cover. Scale bar is 1 km. Location: 39° 45′ 10.80ʺ N, 121° 36′ 52.22ʺ W

Indeed, deforestation is not an unstoppable or irreversible process, and in some parts of the world there has been a shift from net deforestation to net reforestation—a phenomenon called ‘forest transition’ (Mather 1992). This has, for instance, been common around the Mediterranean Sea, where farmland

in marginal areas has been abandoned. The ‘rebirth of the forest’ has also occurred in large tracts of then north eastern USA (Williams 1988). The change in forest cover in a part of Russia following the abandonment of collective farms in postSoviet times is shown in Fig. 2.15.

26

2  Driving Forces

Fig. 2.15  Google Earth images of collective farms in central Russia in 1988 (top) and after abandonment in 2020 (bottom). Scale bar is 6 km. Location: 57° 49′ 15.16ʺ N, 50° 54′ 51.82ʺ E

Introduced invasive plants can also lead to expansion of tree cover in some locations. This is evident in the case of Sharjah in the United Arab Emirates where in recent decades there has been a spread of a South American mesquite,

Prosopis juliflora (Fig. 2.16). Some geomorphological consequences are discussed in Sect. 4.8.4. Tropical deforestation, driven to a great extent by the expansion of farmland, is the second largest source of

2.5 Deforestation

27

Fig. 2.16  Google Earth images of the spread of invasive mesquite woodland in Sharjah, UAE. Scale bar is 800 m. Location: 25° 20′ 34.24ʺ N, 55° 31′ 39.28ʺ E. By 2023, much of this woodland had been cleared

anthropogenic greenhouse gas emissions and a major driver of biodiversity loss (Pendrill et al. 2019). FAO estimates (Lanly et al. 1991) showed that with respect to tropical forests the total annual deforestation in 1990 for 62 countries

(representing some 78% of the tropical forest area of the world) was 16.8 Mha, a figure significantly higher than the one obtained for these same countries for the period 1976– 80 (9.2 Mha per year). Myers (1991) found that there was,

28

however, a considerable variation in the rate of forest regression in different areas within the tropics, with some areas under less severe threat (e.g. western Amazonia, the forests of Guyana, Surinam, and French Guyana, and much of the Zaire Basin in central Africa). Some other areas were being exploited so fast that it was feared that minimal areas would remain, for example, in: the Philippines, peninsular Malaya, Thailand, Australia, Indonesia, Vietnam, Bangladesh, Sri Lanka, Central America, Madagascar, West Africa, and eastern Amazonia. The tropics as a whole lost 11.1 Mha of tree cover in 2021 (https://research.wri.org/gfr/latest-analysisdeforestation-trends) (accessed 7 June 2023), and the situation in Amazonia had been exacerbated by political change. Figure 2.17 shows the transformation that has occurred in Rondônia, Brazil, as farmers have used new roads to gain access to the forest and then to cut it down for cattle pastures. In addition to deforestation itself, large tracts of forest have become degraded (Lapola et al. 2023), a process that is magnified in part by reduced precipitation levels caused by deforestation (Smith et al. 2023). Degradation can also be caused by fires. This degradation reduces biomass and carbon stocks (Fawcett et al. 2023). The drivers of deforestation in Amazonia and the rates at which change are taking place are reviewed by Albert et al. (2023). A major cause of tropical deforestation is soya cultivation. Data for the 1968–2018 period (De Maria et al. 2020) reveals a relentless growth in the total soya bean production levels, in the area harvested and in the average yield for this crop. In 50 years, the world’s soya bean production increased by 8.4 times, the average yield almost doubled, and the global surface devoted to this crop grew by 4.3 times—from 28.8 Mha in 1968, to almost 125 Mha in 2018, which corresponds to an aggregated area larger than the whole South Africa. Song et al. (2021) mapped annual soya bean expansion in South America by combining satellite observations and sample field data. The area cultivated with soya bean more than doubled from 26.4 Mha in 2000 to 55.1 Mha in 2019. Most soya bean expansion occurred on pastures originally converted from natural vegetation for cattle production. They found that the most rapid expansion occurred in the Brazilian Amazon, where soya bean area increased more than ten-fold, from 0.4 Mha to 4.6 Mha. Such an extraordinary growth in global production levels appears to be the combination of two main forces: extensification—that is, the expansion of the soya bean area—and intensification—which can be seen as the increase in average yields due to genetic improvements and better production techniques. Figure 2.18 shows deforestation resulting from soya cultivation in the Santa Cruz area of Bolivia. It had already become evident in 1999, but came to occupy almost the entire area by 2022. The fields radiate out from new settlements as shown in Fig. 2.19. Soya cultivation also takes place in grasslands such as those of the Pampas of

2  Driving Forces

South America. In Uruguay the surface area cultivated with soya beans increased by 1,000% between 1990 and 2020 in Uruguay (Foucher et al. 2023) and caused increased sediment delivery to streams. Another great spasm of deforestation has occurred in the tropics as a result of palm oil production (Wicke et al. 2011), which has increased rapidly over the past 50 years. In 1970, the world was producing only 2 Mt. This is now over 38 times higher: in 2022 the world produced 77 Mt. About 64 Mt of this come from just two countries in southeast Asia: Indonesia and Malaysia. Palm oil is now the most commonly used vegetable oil in the world and is found in many products ranging from cakes and intimate lubricants to lipstick and ice cream. Figure 2.20 shows an area of palm oil plantation that has replaced rainforest in Borneo. Forests are also being cut down to enable ethanol (biofuel) production from sugar cane and maize (Ferrante and Fearnside 2020). Thomaz et al. (2022) review the role that sugar cane plantations can play in generating high soil erosion rates. Particularly in West Africa, concerns have been expressed that forest removal in areas underlain by iron-rich weathering profiles can lead to a process called bowalisation, where erosion created by vegetation removal causes the development of impenetrably hard iron crusts (bowé) (Goudie 1973, p. 65; Padonou et al. 2015).

2.6 Urbanisation Although modest communal settlements may have occurred before the adoption of domestication, it was within a few thousand years of the adoption of cereal agriculture, that people began to gather into ever larger settlements (cities) and into more institutionalised social formations (states). After around 6000 years ago, cities developed in the basin of the Tigris and Euphrates, and more followed by c 5000 years ago in the coastal Mediterranean, the Nile valley, the Indus plain, and coastal Peru. In due course, cities had evolved which had considerable human populations. In Roman times, there were some major cities, some of which were located in arid areas that are now sparsely populated, such as Timgad in the Algerian Sahara (Fig. 2.21). Augustan Rome had a population of around one million and Carthage, at its fall in 146 BC had 700,000. At the present time (2023) there are over 570 urban areas with a population greater than 1 million and 32 with a population over 10 million (https://worldpopulationreview.com/ world-cities) (accessed 7 June 2023). Table 2.1 lists the populations of world mega-cities in 2023. Figure 2.22 shows the dramatic expansion that has taken place in Cairo, Egypt, as a result of the construction of the new urban area of New Cairo (population in 2022 c half a million), while Fig. 2.23

2.6 Urbanisation

29

Fig. 2.17  Google Earth images of deforestation in Rondônia, Brazil. Top in 1988, Bottom in 2020. Scale bar is 90 km. Location: 10° 14′ 7.20ʺ S, 62° 27′ 59.43ʺ W

shows the transformation that has taken place in recent decades of the city of Doha in Qatar. The metropolitan area’s population grew from 89,000 in the 1970s to over 434,000 in 1997 and to 796,947 in 2022. Cities have developed so

much in the Anthropocene, that it has been proposed that cities are themselves landforms (Dixon et al. 2018). Large cities and urban agglomerations have their own environmental effects (Douglas 1983; Chin 2006), sucking

30

2  Driving Forces

Fig. 2.18  Google Earth images of soya fields, Santa Cruz, Bolivia, showing their expansion between 1999 (top) and 2020 (middle). Scale bar is 7 km. Location: 16° 57′ 34.51ʺ S, 62° 15′ 42.76ʺ W

in resources and materials and exporting or storing vast amounts of waste. Figure 2.24 (top) shows a huge mound of landfill that was accumulated in a part of Los Angeles, the Puente Hills. Originally opened in 1957, this was the

largest landfill in the USA, rising 150 m high and covering 2.8 km2. Now closed, the former landfill is in the process of becoming a natural habitat preservation area. Figure 2.24 (middle) shows another large landfill site associated with

2.6 Urbanisation

31

Fig. 2.19  Google Earth image of soya bean village and fields in Santa Cruz Bolivia. Scale bar is 1 km. Location: 16° 57′ 34.51ʺ S, 62° 15′ 42.76ʺ W

Fig. 2.20  Google Earth image of palm oil plantations in western Borneo. These have replaced rainforest. Scale bar is 8 km. Location: 0° 24′ 14.93ʺ S, 109° 25′ 59.29ʺ E

32

2  Driving Forces

Fig. 2.21  Google Earth image of the Roman city of Timgad in Algeria. Scale bar is 200 m. Location: 35° 29′ 6.21ʺ N, 6° 28′ 5.32ʺ E. Timgad is generally regarded as having a population of c 15,000 Table 2.1  Population of world mega-cities in 2023 Tokyo, Japan

37,435,191

Delhi, India

29,399,141

Shanghai, China

26,317,104

Sao Paulo, Brazil

21,846,507

Mexico City, Mexico

21,671,908

Cairo, Egypt

20,484,965

Dhaka, Bangladesh

20,283,552

Mumbai, India

20,185,064

Beijing, China

20,035,455

Osaka, Japan

19,222,665

Las Vegas, Nevada. Figure 2.24 (bottom) shows Asia’s biggest landfill site within Mumbai, India. Erosion rates, runoff, channel forms, and flooding are also affected by urbanisation (see for example the study of Sao Paulo by da Luz and Rodrigues (2015)). Very high rates of erosion are produced while cities are being constructed, when there is much exposed ground and disturbance produced by vehicle movements and excavations. Flooding can be exacerbated by the presence of large areas with impervious surfaces, including concrete road systems of daunting size (see Sect. 4.13.7), and river channels may be altered (see Sect. 4.8.7).

2.7 Mining The rate at which many major minerals are being mined is steadily increasing. This can be illustrated by the statistics for iron ore. In 1974 the world figure was c 900 million tonnes. By 2021 this figure had risen to 2.6 million tonnes, an increase of almost three times. The comparable figures for coal are 3 billion tonnes in 1974 and 8 billion tonnes in 2022, an increase of almost 2.7 times. The landscape effects of mining are legion (Doerr and Guernsey 1956; Lawrence et al. 2023). Mineral extraction produces open-pit mines, strip mines, quarries for structural materials, borrow pits along roads, and similar features. Strip mining can cause exceptional environmental modification and has transformed landscapes in areas such as the lignite (brown coal) fields of central Europe and in Pennsylvania, Ohio, West Virginia, Kentucky, and Illinois in the USA. Strip mining involves mining a seam of mineral, by first removing a long strip of overlying soil and rock (the overburden). There are three forms of strip mining. Firstly, there is Area Stripping, which is used on relatively flat terrain, to extract deposits over a large area. As each long strip is excavated, the overburden is placed in the excavation produced by the previous strip. Secondly, there is Contour Stripping. This consists of removing the overburden in more hilly terrain, where the mineral outcrop usually follows the

2.7 Mining

33

Fig. 2.22  Google Earth images of New Cairo City, Egypt, before and after development. Top: 1991. Bottom: 2020. Scale bar is 5 km. Location: 30° 1′ 26.74ʺ N, 31° 27′ 11.02ʺ E

contour of the land. This method commonly created terraces on mountain sides. Thirdly, there is Mountaintop Removal Mining which employs explosives to blast overburden off the top of some mountains, as in Appalachia (USA) (Reed and Kite 2020). It requires the mass restructuring of

landscape in order to reach the coal seam which can be as much as 300 m below the surface. It causes the replacement of an original steep landscape with a much flatter one (Miller et al. 2014), and large tracts of valleys may be filled in. As a result, significant changes may occur in

34

2  Driving Forces

Fig. 2.23  Google Earth images of the expansion of the urban area of Doha, Qatar, between 1984 (top) and 2020 (bottom). Scale bar is 10 km. Location: 25° 17′ 47.76ʺ N, 51° 30′ 22.55ʺ E

water quality and channel forms (Jaeger 2015). Figure 2.25 shows strip mining taking place for coal in Czechia, while Fig. 2.26 is an image of mountain top removal mining taking place at Hobet in West Virginia, USA. Coal mining

causes land subsidence (see Sect. 8.5), and mining in general can cause landsliding (see Sect. 9.8.4). The depressions associated with some opencast mines are huge (https://www.mining-technology.com/features/

2.7 Mining

35

Fig. 2.24  Google Earth images of landfill sites. Top: Puente Hills Landfill, Los Angeles, USA. Scale bar is 1 km. Location: 34° 2′ 10.02ʺ N, 117° 54′ 1.98ʺ W. Middle: Las Vegas, Nevada, USA. Scale bar is 1 km. Location: 36° 21′ 34.37ʺ N, 114° 54′ 30.45ʺ W. Bottom: Deonar, Mumbai, India. Scale bar is 900 m. Location: 19° 3′ 58.98ʺ N, 72° 55′ 52.03ʺ E

feature-top-ten-deepest-open-pit-mines-world/) (accessed 7 June 2023). Bingham Canyon mine located southwest of Salt Lake City, Utah, USA, is the deepest open-pit mine in the world. It is more than 1.2 km deep and approximately

four kilometres wide. Chuquicamata copper mine in Chile is the second deepest open-pit mine in the world. Also known as the Chuqui open pit, it is 4.3 km long, 3 km wide, and more than 850 m deep. Escondida copper mine located

36

2  Driving Forces

Fig. 2.24  (continued)

Fig. 2.25  Google Earth image of Kadañ opencast coal mine, Czechia. Scale bar is 800 m. Location: 50° 25′ 41.57ʺ N, 13° 19′ 52.42ʺ E

in the Atacama Desert, Chile (Fig. 2.27), ranks as the third deepest open-pit operation. Escondida copper mining operation consists of two open-pit mines, namely Escondida pit and Escondida Norte pit. The Escondida pit is 3.9 km long,

2.7 km wide, and 645 m deep. The Escondida Norte pit is 525 m deep. Udachny diamond mine located in the EasternSiberian Region of Russia is currently the fourth deepest open-pit mine in the world. The Udachny pit is currently

2.7 Mining

37

Fig. 2.26  Google Earth image of Hobet Mine mountain top removal, West Virginia, USA. Scale bar is 3 km. Location: 38° 5′ 13.95ʺ N, 81° 58′ 38.67ʺW

Fig. 2.27  Google Earth image of Escondida copper mine, Chile. Scale bar is 900 m. Location is 24° 12′ 56.60ʺ S, 69° 2′ 47.63ʺ W

38

2  Driving Forces

Fig. 2.28  Top. Google Earth image of Orapa diamond mine, Botswana. Scale bar is 1 km. Location: 21° 19′ 6.68ʺ S, 25° 23′ 1.88ʺ E. Bottom. Google Earth image of Rössing uranium mine, Namibia. Scale bar is 1 km. Location: 22° 29′ 0.33ʺ S, 15° 3′ 32.17ʺ E

630 m deep. Muruntau mine in Uzbekistan, one of the largest open-pit gold mines in the world, ranks as the fifth deepest open pit. It is 3.5 km long and 3 km wide. The depth of the mine has reached just over 600 m. The Fimiston open pit, also known as the Super Pit, located on southeast edge

of Kalgoorlie, Western Australia, is the sixth deepest openpit mine in the world. This gold-producing pit is 3.8 km long, 1.5 km wide, and up to 600 m deep. Grasberg mine, located in the Papua Province of Indonesia, currently ranks as the world’s seventh deepest open-pit operation. It is

2.7 Mining

39

Fig. 2.29  Google Earth image of alluvial diamond workings along the coastline of southern Namibia. Scale bar is 6 km. Location: 28° 26′ 48.54ʺ S, 16° 16′ 26.64ʺ E

more than 550 m deep and is the largest gold mine in the world. Betze-Post pit in Nevada, USA, is the eighth deepest open-pit mine. This gold-producing open pit is about 2.2 km long and 1 km wide. Its depth is well over 500 m. Figure 2.28 (top) shows the deep pit created by diamond mining of kimberlite pipes at Orapa in Botswana. Opened in 1971, currently Orapa is mining at a depth of 305 m and is expected to reach 350 m by 2026. Another large pit in southern Africa is the uranium mine at Rössing in Namibia (Fig. 2.28, bottom). Not all diamond mining requires the excavation of deep pits. Along the coast of southern Namibia, the diamonds are removed by excavation of shallow pits, which then become flooded (Fig. 2.29). These diamonds have an alluvial origin and are thought to have originated from kimberlite pipes in the interior of South Africa. The diamonds were transported down to the Atlantic Ocean by the Orange and other river systems and then carried northward along the Namibian coast by ocean currents to be deposited either on the shallow ocean bottom or along the coastline. They are placer deposits (Kirkpatrick et al. 2019). Mining activity can produce tailing dams. Mine tailings are pulverised rock that remains after the valuable metal-bearing minerals have been extracted in physical separation processes. They are discharged into an impoundment as a slurry containing ∼30 wt% solids. They can be dangerous sources of toxic chemicals such as heavy metals

and radioactive content. The ponds are also vulnerable to major breaches or leaks from the dams that restrain them (Armstrong et al. 2019), causing environmental disasters as occurred at an aluminium nine at Barcarena in Brazil in 2018. Figure 2.30 (top) shows the tailing pond at this location. Figure 2.30 (bottom) shows tailings at the Mount Isa copper and lead mine in Queensland, Australia. Once abandoned, tailing dam deposits may be subject to gullying and piping (Duque et al. 2015) and be subject to high rates of water erosion (Peña-Ortega et al. 2019) and wind attack, as is the case with the mine dumps (see Fig. 3.11) of the Witwatersrand goldfield in South Africa (Ojelede et al. 2012). Mine tailings can also cause coastal progradation to occur, as has happened with copper mine debris on the coast of Chile (Paskoff and Petiot 1990). They also lead to major changes in floodplain morphology, as in the Loddon Valley of Victoria, Australia (Lawrence et al. 2023). Oil mining can radically change landscapes. Figure 2.31 shows this in the context of the Baldwin Hills in the heart of Los Angeles. It can also cause pollution as revealed in the image of an oil spill in Kuwait (Fig. 2.32). One particular type of oil mining is that employed for the exploitation of the Athabasca tar sands in NE Alberta, Canada. These are large deposits of bitumen or extremely heavy crude oil. Their exploitation is partially by surface strip mining, and some of the residues are stored in toxic tailings ponds. Figure 2.33 shows the growth of the

40

2  Driving Forces

Fig. 2.30  Tailing dams. Top: Google Earth image of Barcarena mine tailings, Brazil. Scale bar is 1 km. Location: 1° 32′ 50.13ʺ S, 48° 42′ 46.85ʺ W. Bottom: Google Earth image of Mount Isa mine tailings, Queensland, Australia. Scale bar is 5 km. Location: 20° 44′ 28.69ʺ S, 139° 27′ 17.29ʺ E

mine from 1984 to 2020. The environmental consequences are discussed by Culp et al. (2021). Humans now have the technological ability to shift huge amounts of sediments, including aggregates used in the construction industry. Cooper et al. (2018, p. 222) argued

that ‘the annual direct anthropogenic contribution to the global production of sediment in 2015 was conservatively some 316 Gt (150 km3), a figure more than 24 times greater than the sediment supplied annually by the world’s major rivers to the oceans’.

2.7 Mining

41

Fig. 2.31  Google Earth image of oil wells, Baldwin Hills, Los Angeles, California, USA. Scale bar is 300 m. Location: 34° 0′ 13.46ʺ N, 118° 22′ 17.10ʺ W

Fig. 2.32  Google Earth image of oil spill in Kuwait. Scale bar is 500 m. Location: 28° 51′ 52.86ʺ N, 47° 46′ 41.61ʺ E

42

2  Driving Forces

Fig. 2.33  Google Earth images of the increasing exploitation of the Athabasca tar sands, Alberta, Canada, between 1984 (top) and 2020 (bottom). Scale bar is 30 km. Location: 57° 7′ 25.79ʺ N, 111° 22′ 20.46ʺ W

2.8 Energy Sources and the Landscape The scale of current energy use by humans is enormous. As a result, driven by the accelerated burning of hydrocarbon fuels, atmospheric temperatures increased by 0.9 °C in the last 70 years, with much of the rise post-dating 1970. Atmospheric

CO2 levels reached 415 ppm in 2019, which is higher than at any time in the past 3 million years. Syvitski et al. (2020) have estimated that since 1950 CE, energy consumption by humanity has averaged 61 GJ/y per capita. In total, they estimated that 60% of all human-produced energy has been consumed since 1950 CE, more than in the entire previous Holocene.

2.8  Energy Sources and the Landscape

43

Fig. 2.34  Google Earth image of hillslopes scarred by seismic lines used for oil exploration at Fahud in Oman. Scale bar is 1 km. Location: 22° 18′ 10.74ʺ N, 56° 25′ 48.14ʺ E

Fig. 2.35  Google Earth image of fracking infrastructure in New Mexico, USA. Scale bar is 800 km. Location: 32° 35′ 18.39ʺ N, 104° 28′ 41.30ʺ W

The search for energy sources has had an impact on many landscapes, as for example, in the Middle East. In Oman, the land surface on the flanks of Jebel Fahud has been

scarred by a network of seismic lines used in oil prospecting (Fig. 2.34). Seismic lines are narrow linear clearings created during hydrocarbon exploration, and they can persist in

44

2  Driving Forces

Fig. 2.36  Google Earth images of developing lithium exploitation from a salt lake in Chile, between 1993 (top) and 2020 (middle). Scale bar is 30 km. Location: 23° 26′ 55.55ʺ S, 68° 18′ 16.23ʺ W. Bottom: close up of Salar de Atacama lithium ponds in 2020. Scale bar is 3 km. Location: 23° 32′ 45.08ʺ S, 68° 23′ 30.13ʺ W

the landscape. For example, many conventional seismic lines in the boreal ecosystems of northern Alberta have shown little recovery over the past 30–40 years. Seismic operations within permafrost regions can also result in rutting and

subsidence of the ground surface, changes in albedo and net radiation, and changes in ground thermal and moisture regimes, which all contribute to permafrost thaw and damage (Dabros et al. 2018; Braverman and Quinton 2016).

2.8  Energy Sources and the Landscape

45

Fig. 2.36  (continued)

In places like Kuwait and Texas the oil wells themselves have scarred the landscape. Fracking wells can also transform landscapes (Fig. 2.35). Shale gas production by fracking in the USA climbed from only 60 billion m3 in 2008 to 792 in 2021, a 13-fold increase (https://www.eia.gov/dnav/ng/hist/ res_epg0_r5302_nus_bcfa.htm) (accessed 7 June 2023).

In the rush to reduce carbon emissions into the atmosphere, new energy sources are being developed, and they also have an environmental impact. This can be illustrated from the Salar de Atacama, Chile (Fig. 2.36), where the salt lake has been modified by plants for the extraction of lithium, an essential component of electric batteries (Bustos-Gallardo et al. 2021; Garcés

Fig. 2.37  Google Earth image of wind turbines near Mojave, California, USA. Scale bar is 400 m. Location: 35° 4′ 19.26ʺ N, 118° 15′ 51.94ʺ W

46

2  Driving Forces

Fig. 2.38  Solar farms. Top: Google Earth image of Moroccan solar farm. Scale bar is 1 km. Location: 31° 3′ 37.79ʺ N, 6° 52′ 9.86ʺ W. This is the Noor-Ouarzazate complex, the world’s largest concentrated solar power plant, an enormous array of curved mirrors spread over 3000 ha which concentrate the sun’s rays towards tubes of fluid, with the hot liquid then used to produce power. Bottom: Google Earth image of the more conventional Toujounine solar farm near Nouakchott in Mauritania. Scale bar is 900 m. Location: 18° 5′ 31.63ʺ N, 15° 53′ 24.61ʺ W

2.8  Energy Sources and the Landscape

47

Fig. 2.39  Top: Tidal power. Google Earth image of La Rance tidal barrage, Brittany, France. Scale bar is 1 km. Location: 48° 37′ 4.10ʺ N, 2° 1′ 14.62ʺ W. Bottom: Google Earth image of Sihwa Lake tidal barrage, South Korea. Scale bar is 7 km. Location: 37° 18′ 45.32ʺ N, 126° 40′ 52.83ʺ E

48

2  Driving Forces

Fig. 2.40  Google Earth image of pumped hydrostorage scheme, Bath County, Virginia, USA. Scale bar is 3 km. Location: 38° 13′ 17.16ʺ N, 79° 48′ 15.13ʺ W

and Álvarez 2020). The Salar contains the largest lithium reserve yet found globally. In 2010 global lithium production was 28,100 metric tonnes and in 2021 was 105,000 (https:// www.weforum.org/agenda/2023/01/chart-countries-producelithium-world/) (accessed 7 June 2023). Global wind power generation has increased more than five-fold from 342.7 TWh in 2010 to 1870.3 in 2021 (https://www.iea.org/reports/wind-electricity) (accessed 7 June 2023) (Fig. 2.37). As regards solar power globally this has grown ten-fold from around 100 GW of solar capacity in 2012 to c 1000 GW (1 TW) in 2022 (https://www.solarpowereurope.org/ news/2022-the-year-of-terawatt-solar) (accessed 7 June 2023). Large scale solar and wind power plants can cause extensive areas of land degradation and habitat loss, and their installation has led to vegetation removal, land grading, soil compaction, and construction of access roads. The possible impacts of such activities include soil erosion, increased sediment load or turbidity in streams, reduction of groundwater recharge, and increased likelihood of flooding. If the solar power plant site is on a slope, access roads between the panels can cause erosion (Dhar et al. 2020). Solar farms are getting increasingly large, as is the case, for example, with the Tengger Desert Solar Park in China, the Benban Solar Park near Aswan in Egypt, the Ivanpah Solar Farm in California, USA, the Bhadla and Pavagada solar farms in India, and the

Mohammed bin Rashid Al Maktoum Solar Park in the UAE (https://ornatesolar.com/blog/the-5-largest-solar-power-plantsin-the-world#:~:text=Bhadla%20Solar%20Park%20is%20 the,of%20over%201.3%20billion%20dollars) (accessed 7 June 2023). Figure 2.38 (top) shows a solar farm in Morocco, and Fig. 2.38 (bottom) shows a solar farm in Mauritania. Another source of renewable energy is tidal power. As yet this is not very widespread, but in Brittany, northern France there is the La Rance tidal barrage (Fig. 2.39, top). This was opened in 1966. For 45 years it was the largest tidal power station in the world by installed capacity until it was surpassed by the South Korean Sihwa Lake Tidal Power Station in 2011 (Fig. 2.39, bottom). In some countries a recent development in the energy sector has been the production of biofuels from such crops as sugar cane and maize. World bio-ethanol production increased by 67%, from 67 to 110.4 billion litres, over the decade 2008–2018 (Jeswani et al. 2020). This has implications for land use and land cover changes. Finally, pumped hydrostorage schemes are becoming more important. In these water is pumped up to a feeder reservoir when solar or wind power is operating powerfully or demand is low, and then when the demand is high, water released from the reservoir powers electricity generating turbines as the flow returns to a lower point in the landscape. This is illustrated for Bath County in Virginia, USA (Fig. 2.40).

2.9 Tourism

49

Fig. 2.41  Google Earth images of new tourist facilities on the coastline to the south of Ras Al Khaimah in 2009 (top) and 2023 (bottom). Scale bar is 5 km. Location: 25° 42′ 18.76ʺ N, 55° 48′ 55.99ʺ E

2.9 Tourism A major sector that has developed in recent decades is that of tourism. This is because of the availability of relatively cheap and easy foreign air travel, the expansion in the use of

cars, and the burgeoning cruise industry. In 1950 there were 25 million international tourist arrivals, and in 1970 the number was 166 million. By 1995 the number of international tourist arrivals was 1.08 billion, and by 2019 this figure had reached 2.4 billion (https://data.worldbank.org/indicator/

50

2  Driving Forces

Table 2.2  Some geomorphological consequences of global heating (modified from Goudie 2022) Hydrological Increased evapotranspiration loss leading to river flow diminution, lake desiccation, less soil cohesion, etc Overall increase in global precipitation leading to increased flood activity Greater rainfall extremes Increased percentage of precipitation as rainfall at expense of winter snowfall leading to changes in snowpack and in river regimes Increased snowfall in very high latitudes leading to changes in river regimes Possible increased risk of tropical cyclones (greater latitudinal spread, frequency, rainfall, and intensity) Changes in state of lakes, wetlands, and peatbogs Less use of water by vegetation because of increased CO2 effect on stomatal closure Vegetation controls Major changes in latitudinal extent and position of biomes—reduction in boreal forest, increase in grassland and drylands, rainforest shrinkage because of droughts, poleward migration of mangroves, decline of seagrasses, etc. Major changes in altitudinal distribution of vegetation types (i.e. 500 m for 3 °C) Growth enhancement by CO2 fertilisation Changes due to increases in fire frequencies Cryospheric Permafrost decay, thermokarst, increased thickness of active layer, active layer detachments, instability of slopes, and degradation of river banks and shorelines Changes in glacier and ice sheet rates of ablation and accumulation: glacier retreat Changes in glacier lakes and outburst floods Removal of glacial buttresses from slopes, leading to slope instability Sea ice melting, increasing wave attack conditions in polar regions Changes in snowpack extent Coastal Inundation of low-lying areas by sea level rise (including wetlands, deltas, swamps, marshes, reefs, lagoons, etc.) Accelerated coast recession (particularly of sandy beaches) Changes in rates of reef growth and coral bleaching Spread of mangrove swamps into higher latitudes Storm surge erosion and overtopping Aeolian Increased dust storm activity in areas of moisture deficit, but reduced activity in areas of global stilling Dust deflation from desiccating lakes Dune reactivation in areas of moisture deficit Soil erosion Changes in response to changes in land use, fires, natural vegetation cover, rainfall erosivity, etc. Changes resulting from soil erodibility modification (e.g. sodium and organic contents) Subsidence Desiccation of clays under conditions of increased summer drought Thermokarst as a result of permafrost melting Increased oxidation of organic soils under higher temperatures Great groundwater exploitation to cope with increased droughts Weathering Reduction in number of freeze–thaw cycles Salt weathering changes in response to groundwater levels and temperature and humidity transitions Increased thermal expansion of minerals Changes in silicate and carbonate mineral solubility

ST.INT.ARVL) (accessed 31 May 2023). The environmental consequences include pollution, destruction of vegetation cover, overuse of water resources, erosion (see Chap. 6 in Holloway and Humphreys 2019), and degradation of heritage sites. Construction of hotels can transform a coastline, as has been the case south of Ras Al Khaimah in the United Arab Emirates, where sabkha wetlands and lagoons have effectively disappeared (Fig. 2.41). On the positive side, safaris in countries like Botswana, Namibia, and Kenya provide money and motivation for conservation work.

2.10 Climate Change Finally, climate change caused by humans has become a major cause of landscape change, especially since the 1970s (Table 2.2). Human-induced global warming, produced primarily by the emission of a cocktail of greenhouse gases has caused global heating, is occurring. Global surface temperature was around 1.1 °C above 1850–1900 in 2011–2020. The consequences of this are apparent in terms not only of rising temperatures, but also in terms of the occurrence of extreme

References

weather events such as floods droughts and tropical cyclones, of rising sea levels, of glacier and permafrost decay, of shifting vegetation belts, of fire occurrence, of snowpack extent, of dune mobility, and many other consequences (see Chaps. 8–12 in Goudie 2018). Full details are provided by the reports of the Intergovernmental Panel on Climate Change in 2021 (https://report.ipcc.ch/ar6/wg1/), 2022 (https://www. ipcc.ch/report/ar6/wg2/), and 2023 (https://report.ipcc.ch/ ar6syr/pdf/IPCC_AR6_SYR_LongerReport.pdf) (accessed 31 May 2023).

References Albert JS et al (2023) Human impacts outpace natural processes in the Amazon. Science 379(6630):eabo5003 Aleman JC, Jarzyna MA, Staver AC (2018) Forest extent and deforestation in tropical Africa since 1900. Nature Ecol Evol 2(1):26–33 Alley WM, Alley R (2017) High and dry: Meeting the challenges of the world’s growing dependence ongroundwater. Yale Univ Press, New Haven p. 304 Andela N et al (2017) A human-driven decline in global burned area. Science 356:1356–1362 Anderson EP et al. (2018) Fragmentation of Andes-to-Amazon connectivity by hydropower dams. Sci Adv 4(1):eaao1642 Armstrong M, Petter R, Petter C (2019) Why have so many tailings dams failed in recent years? Resour Policy 63:101412 Baker TL (1989) Irrigating with windmills on the Great Plains. Gt Plains Q 9:216–230 Bar-On YM, Phillips R, Milo R (2018) The biomass distribution on Earth. Proc Nat Acad Sci 115(25):6506–6511 Barlow PM, Reichard EG (2010) Saltwater intrusion in coastal regions of North America. Hydrogeol J 18:246–270 Bencherif MC (2008) Touggourt or the dynamics of a city with seven ksour. Sci Technol d, Earth Sci 18:9–18 Braverman M, Quinton WL (2016) Hydrological impacts of seismic lines in the wetland-dominated zone of thawing, discontinuous permafrost, Northwest Territories, Canada. Hydrol Proc 30(15):2617–2627 Bustos-Gallardo B, Bridge G, Prieto M (2021) Harvesting Lithium: water, brine and the industrial dynamics of production in the Salar de Atacama. Geoforum 119:177–189 Chen Y, Chang Z, Xu S, Qi P, Tang, X, Song Y, Liu D (2021) Altitudinal gradient characteristics of spatial andtemporal variations of snowpack in the Changbai Mountain and their response to climate change. Water13(24):3580 Chin A (2006) Urban transformation of river landscapes in a global context. Geomorphology 79:460–487 Cooper AH, Brown TJ, Price SJ, Ford JR, Waters CN (2018) Humans are the most significant global geomorphological driving force of the 21st century. Anthrop Rev 5:222–229 Culp JM et al (2021) Ecological effects and causal synthesis of oil sands activity impacts on river ecosystems: water synthesis review. Environ Rev 29(2):315–327 Dabros A, Pyper M, Castilla G (2018) Seismic lines in the boreal and arctic ecosystems of North America: environmental impacts, challenges, and opportunities. Environ Rev 26(2):214–229 da Luz RA, Rodrigues C (2015) Anthropogenic changes in urbanised hydromorphological systems in a humid tropical environment: River Pinheiros, Sao Paulo, Brazil. Z Geomorph Suppl 59:109–135 Daliakopoulos IN, Tsanis IK, Koutroulis A (2016) The threat of soil salinity: a European scale review. Sci Total Environ 573:727–739 Darby HC (1956) The clearing of the woodland in Europe. In: Thomas WF (ed) Man’s role in changing the face of the Earth. University of Chicago Press, Chicago, pp 183–216

51 De Maria M et al. (2020) Global soybean trade. The geopolitics of a bean. UK Research and Innovation Global Challenges Research Fund (UKRI GCRF) Trade, Development and the Environment Hub. https://doi.org/10.34892/7yn1-k494. Accessed 18th July 2023 Dethier DP, Ouimet WB, Murphy SF, Kotikian M, Wicherski W, Samuels RM (2018) Anthropocene landscape change and the legacy of nineteenth-and twentieth-century mining in the Fourmile Catchment, Colorado Front Range. Ann Ass Am Geogr 108:917–937 Dhar P (2020) The carbon impact of artificial intelligence. Nat Mach Intell 2:423–425 Dhar A, Naeth MA, Jennings PD, El-Din MG (2020) Perspectives on environmental impacts and a land reclamation strategy for solar and wind energy systems. Sci Total Environ 718:134602 Dixon SJ, Viles HA, Garrett BL (2018) Ozymandias in the Anthropocene: the city as an emerging landform. Area 50(1):117–125 Doerr A, Guernsey L (1956) Man as a geomorphological agent: the example of coal mining. Ann Ass Am Geogr 46(2):197–210 Douglas I (1983) The urban environment. Arnold, London, p 240 Duque JM, Zapico I, Oyarzun R, García JL, Cubas P (2015) A descriptive and quantitative approach regarding erosion and development of landforms on abandoned mine tailings: new insights and environmental implications from SE Spain. Geomorphology 239:1–6 Estoque RC et al (2022) Spatiotemporal pattern of global forest change over the past 60 years and the forest transition theory. Environ Res Lett 17(8):084022 Eswar D, Karuppusamy R, Chellamuthu S (2021) Drivers of soil salinity and their correlation with climate change. Current Opinion Environ Sustain 50:310–318 Fawcett D et al (2023) Declining Amazon biomass due to deforestation and subsequent degradation losses exceeding gains. Glob Change Biol 29(4):1106–1118 Ferrante L, Fearnside PM (2020) The Amazon: biofuels plan will drive deforestation. Nature 577:170–171 Fluet-Chouinard E et al (2023) Extensive global wetland loss over the past three centuries. Nature 614:281–286 Foucher A et al (2023) Inexorable land degradation due to agriculture expansion in South American Pampa. Nat Sustain 6:662–670 Garcés I, Álvarez G (2020) Water mining and extractivism of the Salar de Atacama, Chile. WIT Trans Ecol Environ 245:189–199 Gautney JR, Holliday TW (2015) New estimations of habitable land area and human population size at the Last Glacial Maximum. J Archaeol Sci 58:103–112 Goudie AS (1973) Duricrusts in tropical and subtropical landscapes. Clarendon Press, Oxford, p 174 Goudie AS (2018) The human impact on the natural environment. Wiley Blackwell, Oxford, p 458 Goudie AS (2022) Introduction: geomorphology at the start of the twenty-first century. In: dos Santos BG, Felippe MF, Neto MR (eds) Geomorphology of Brazil: complexity, interscale and landscape. Springer, Cham, pp 1–24 Goudie AS, Viles HA (1997) Salt weathering hazard. Wiley, Chichester, p 256 Goudie AS, Viles HA (2016) Geomorphology in the anthropocene. Cambridge University Press, Cambridge, p 380 Hamad SM, Ahweej YA (2020) Evaluation of the Nubian sandstone aquifer system (NSAS) in Al Kufra Oasis, Southeast Libya. Desalin Water Treat 176:105–113 Jaeger KL (2015) Reach-scale geomorphic differences between headwater streams draining mountaintop minedand unmined catchments. Geomorphology 236:25–33 Jeswani HK, Chilvers A, Azapagic A (2020) Environmental sustainability of biofuels: a review. Proc Roy Soc A 476(2243):20200351 Jolly WM, Cochrane MA, Freeborn PH (2015) Climate-induced variations in global wildfire danger from 1979 to 2013. Nat Commun 6. https://doi.org/10.1038/ncomms8537 Jones MW, Smith A, Betts R, Canadell JG, Prentice IC, Le Quéré C (2020) Climate change increases the risk of wildfires. Sci Brief Rev 116:117

52 Kalischek N et al (2023) Cocoa plantations are associated with deforestation in Côte d’Ivoire and Ghana. Nature Food 4(5):384–393 Kaplan JO, Krumhardt KM, Zimmermann N (2009) The prehistoric and preindustrial deforestation of Europe. QuatSci Rev 28:3016–3034 Khelifi Touhami M, Bouraoui S, Berguig MC (2020) Contribution of Sentinel-2 multispectral satellite images to study salinization effect of the Touggourt agricultural region (Algeria). Arab J Geosci 13(13):1–12 Kirkpatrick LH, Jacob J, Green AN (2019) Beaches and bedrock: how geological framework controls coastal morphology and the relative grade of a Southern Namibian diamond placer deposit. Ore Geol Rev 107:853–862 Kustu MD, Fan Y, Robock A (2010) Large-scale water cycle perturbation due to irrigation pumping in the US High Plains: a synthesis of observed streamflow changes. J Hydrol 390:222–244 Holloway JC, Humphreys C (2019) The business of tourism. Sage, London, p 744 Lanly JP, Singh KD, Janz K (1991) FAO’s 1990 reassessment of tropical forest cover. Nature Resour 27:21–26 Lapola DM et al (2023) The drivers and impacts of Amazon forest degradation. Science 379(6630):eabp8622 Latrubesse EM, Arima EY, Dunne T (2017) Damming the rivers of the Amazon basin. Nature 546:363–369 Lawrence S et al (2023) Characterising mine wastes as archaeological landscapes. Geoarchaeology. https://doi.org/10.1002/gea.21958 Mather AS (1992) The forest transition. Area 24:367–379 Mazzoni A, Heggy E, Scabbia G (2018) Forecasting water budget deficits and groundwater depletion in the main fossil aquifer systems in North Africa and the Arabian Peninsula. Glob Environ Change 53:157–173 McNeill JR, Engelke P (2016) The great acceleration. Harvard University Press, Cambridge, Massachusetts, p 288 Miller JD, Kim H, Kjeldsen TR, Packman J, Grebby S, Dearden R (2014) Assessing the impact of urbanization on storm runoff in a peri-urban catchment using historical change in impervious cover. J Hydrol 515:59–70 Moran EF, Lopez MC, Moore N, Müller M, Hyndman DW (2018) Sustainable hydropower in the 21st century. Proc Nat Acad Sci 115:11891–11897 Myers N (1991) Tropical forests: present status and future outlook. Clim Change 19(1–2):3–32 Nitschke CR, Innes JL (2013) Potential effect of climate change on observed fire regimes in the Cordilleran forests of South-Central Interior, British Columbia. Clim Change 116:579–591 Ojelede ME, Annegarn HJ, Kneen MA (2012) Evaluation of aeolian emissions from gold mine tailings on the Witwatersrand. Aeol Res 3(4):477–486 Padonou EA, Lykke AM, Bachmann Y, Sinsin B (2015) Bowalization: its impact on soil, biodiversity, and human livelihoods in West Africa. Adv Environ Res 40:187–198 Paskoff R, Petiot R (1990) Coastal progradation as a by-product of human activity: an example from Chañaral Bay, Atacama Desert, Chile. J Coastal Res 6:91–102 Peña-Ortega M et al (2019) Environmental assessment and historic erosion calculation of abandoned mine tailings from a semi-arid zone of northwestern Mexico: insights from geochemistry and unmanned aerial vehicles. Environ Sci Poll Res 26:26203–262015 Pendrill F, Persson UM, Godar J, Kastner T, Moran D, Schmidt S, Wood R (2019) Agricultural and forestry trade drives large share of tropical deforestation emissions. Global Environ Change 56:1–10 Reed M, Kite S (2020) Peripheral gully and landslide erosion on an extreme anthropogenic landscape produced by mountaintop removal coal mining. Earth Surf Proc Landf 45(9):2078–2090 Remini B, Achour B, Albergel J (2011) Timimoun’s foggara (Algeria): an heritage in danger. Arab J Geosci 4:495–506 Richards JF (1991) Land transformation. In: Turner BL, Clark WC, Kates RW, Richards JF, Matthews JT, Meyer WB (eds) The Earth

2  Driving Forces as transformed by human action. Cambridge University Press, Cambridge, pp 163–178 Roberts P, Boivin N, Kaplan JO (2018) Finding the anthropocene in tropical forests. Anthropocene 23:5–16 Scanlon BR, Faunt CC, Longuevergne L (2012) Groundwater depletion and sustainability of irrigation in the US High Plains and Central Valley. Proc Nat Acad Sci 109:9320–9325 Scerri EM, Roberts P, Yoshi Maezumi S, Malhi Y (2022) Tropical forests in the deep human past. Phil Trans Roy Soc B, 377(1849):20200500 Siebert S, Burke J, Faures JM, Frenken K, Hoogeven J, Döll P, Portman FT (2010) Groundwater use for irrigation—a global inventory. Hydrol Earth System Sci Disc 7:3977–4021 Smith C, Baker JC, Spracklen DV (2023) Tropical deforestation causes large reductions in observed precipitation. Nature 615(7951):270–275 Soja AJ, Tchebakova NM, French NH (2007) Climate-induced boreal forest change: predictions versus current observations. Glob Planet Change 56:274–296 Song XP et al (2021) Massive soybean expansion in South America since 2000 and implications for conservation. Nat Sustain 4(9):784–792 Sophocleous M (2010) Review: groundwater management practices, challenges, and innovations in the High Plains aquifer, USA—lessons and recommended actions. Hydrogeol J 18:559–575 Suzzi-Simmons A (2023) Status of deforestation of Madagascar. Glob Ecol Conserv 42:e02389 Syvitski J et al (2020) Extraordinary human energy consumption and resultant geological impacts beginning around 1950 CE initiated the proposed Anthropocene Epoch. Comm Earth Environ 1(1):1-13 Thomaz EL, Marcatto FS, Antoneli V (2022) Soil erosion on the Brazilian sugarcane cropping system: an overview. Geogr Sustain 3:129–138 Thorslund J, Bierkens MF, Oude Essink GH, Sutanudjaja EH, van Vliet MT (2021) Common irrigation drivers of freshwater salinisation in river basins worldwide. Nat Commun 12(1):423 Tyukavina A et al (2022) Global trends of forest loss due to fire from 2001 to 2019. Frontiers Remote Sens 15. https://doi.org/10.3389/ frsen.2022.825190 Wada Y, van Beek LPH, van Kempen CM, Reckman JWTM, Vasak S, Bierkens MFP (2010) Global depletion of groundwater resources. Geophys Res Lett 37:L20402. https://doi. org/10.1029/2010GL044571 Whittaker RJ, Fernández-Palacios JM, Matthews TJ (2003) Island biogeography. Oxford University Press, Oxford, p 475 Wicke B, Sikkema R, Dornburg FA (2011) Exploring land use changes and the role of palm oil production in Indonesia and Malaysia. Land Use Policy 28:193–206 Wilkinson JC (1977) Water and tribal settlement in South-East Arabia: a study of the Aflāj of Oman. Clarendon Press, Oxford, p 276 Williams M (1988) The death and rebirth of the American forest: clearing and reversion in the United States, 1900–1980. In: Richards JF, Tucker R (eds) World deforestation in the twentieth century. Duke University Press, Durham, North Carolina, pp 211–229 Williams M (1989) Americans and their forests. Cambridge University Press, Cambridge, p 624 Williams M (2003) Deforesting the Earth. From prehistory to global crisis. Univ Chicago Press, Chicago, p 716 Youssef AM, Sabtan AA, Maerz NH, Zabramawi YA (2014) Earth fissures in Wadi Najran Kingdom of Saudi Arabia. Nat Hazards 71(3):2013–2027 Yu Y, Ginoux P (2022) Enhanced dust emission following large wildfires due to vegetation disturbance. Nat Geosc 15(11):878–884 Zarfl C, Lumsdon AE, Berlekamp J, Tydecks L, Tockner K (2015) A global boom in hydropower dam construction. Aquatic Sci 77:161–170

3

Humanly-Made Landforms

Abstract

Humans have changed landscapes during the Palaeoanthropocene and Anthropocene by creating a whole range of artificial landforms, some of considerable antiquity. These include tells and other mounds, tumuli, hillforts, defensive walls, moated settlements, qanat, terraces and lynchets, soil heaps from mines, and craters produced by warfare.

Keywords

Anthropogeomorphology · Craters · Defensive structures · Landforms · Qanat · Spoil heaps · Tells · Terraces · Tumuli

3.1 Introduction Anthropogeomorphology studies both the nature of deliberate land forming processes (Szabó et al. 2010), such as the creation of sea walls, artificial islands, embankments and levees, spoil heaps, agricultural terraces, mines, quarries, canals and reservoirs, and the less deliberate changes in the operation of processes (Goudie and Viles 2016). As we saw in Chap. 2, various driving forces—deforestation, grazing, urbanisation, air pollution, energy production, construction, and hydrological manipulation—have a wide range of impacts (Tarolli et al. 2019). Table 3.1 lists some major anthropogeomorphic processes. In this chapter we consider some individual landscape phenomena produced in the Palaeoanthropocene and Anthropocene.

3.2 Tells and Other Mounds Long-continued settlement in roughly the same location leads over time to the accumulation of waste products, such as dung and ash, and the remains of generations of decaying mud, rammed earth, brick, and stone buildings. These accumulations give rise to large mounds that are normally called tells (chogha or tepe in Farsi, and hoyuk in Turkish) (Blanco-González and Kienlin 2020). They occur in many parts of the world, including Mesoamerica (Hall 1994), West Africa (Macdonald 1997), Europe (Lubos et  al. 2011), Iran (Maghsoudi et al. 2014), India, and, above all, Mesopotamia and other long-settled parts of the Middle East (Menze and Ur 2012). Many of them date back to the beginnings of urban settlement in the early Holocene. At the present time, remote sensing has shown that many are being destroyed or looted (Elfadaly et al. 2019). A large tell from Syria, Tell Brak, is shown in Fig. 3.1. It is one of the largest ancient tells in northern Mesopotamia, over 40 m high and 800  ×  600 m in area. The main mound was occupied from at least 6000 BC to the late 2nd millennium BC, or the end of the Late Bronze Age (Middle Assyrian Period). In its heyday during the Late Chalcolithic period (4th millennium BC), the site covered an area of some 110–160 ha, with a population estimate of between 17,000 and 24,000 (https://www.thoughtco.com/ tell-brak-mesopotamian-capital-syria-170274). Another class of mound is that constructed as a protective measure against storm tides on the North Sea coast of Germany and the Netherlands. Such mounds, called Wurten, were constructed before dyke construction commenced about a thousand years ago. In the Americas there are many mounds which were constructed for a range of purposes, including for temples, burial, and settlement (Denevan 1992). In the mid-west and south of the USA there may be as many as several hundred thousand artificial mounds that largely predate European colonisation, and some are enormous. Notable is a mound at Cahokia,

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 A. Goudie, Landscapes of the Anthropocene with Google Earth, https://doi.org/10.1007/978-3-031-45385-4_3

53

54 Table 3.1  Some major anthropogeomorphic processes (modified from Goudie 2022)

3  Humanly-Made Landforms Direct processes Constructional Causeways Defensive walls Embankments (e.g. on railways) Fort construction Moulding Ploughing (lynchets) Raised fields Reclamation Terracing Tipping Tumulus and burial mound building Refuse disposal Excavational Blasting of materials Churning Cratering by warfare Cutting Digging Mining Moats Seismic lines Trampling Tunnelling for qanat Hydrological Canal construction Channel modification (e.g. straitening and levees) Coastal protection Damming Draining Dredging Flooding Lake desiccation River diversions Indirect processes Acceleration of erosion and sedimentation Agricultural activity and clearance of vegetation Engineering, especially road construction and urbanisation Modifications of hydrological regime by dams, reservoirs, etc. Subsidence: collapse, settling Draining and desiccation of organic soils Ground fissures following groundwater removal Hydraulic (e.g. groundwater and hydrocarbon pumping) Mining (e.g. of coal and salt) Thermokarst (melting of permafrost) Slope failure: landslides, flows, accelerated creep Loading by spoil, buildings, etc. Lubrication by irrigation water, broken sewers, etc. Shaking and vibration Undercutting by road construction, etc. Vegetation removal by fire Seismic activity Fracking Loading by reservoirs Lubrication along fault planes Weathering Accelerated salinisation following changes in groundwater levels, deicing salt applications, etc. Acidification of precipitation by sulphate and nitrate emissions Lateritisation (bowalisation) following vegetation removal

55

3.3 Tumuli

Fig. 3.1  Google Earth image of Tell Brak, Syria. Scale bar is 400 m. Location: 36° 40′ 5.25ʺ N, 41° 3′ 32.33ʺ E

near St. Louis, which is 30.5 m high and covers an area of 6.9 ha (Peet 1891) (Fig. 3.2). It is a World Heritage Site (https://whc.unesco.org/en/list/198/). Cahokia was a large, pre-Columbian settlement that flourished between 1000 and 1300 AD, before being abandoned. The city associated with the site contained an estimated population of approximately 20,000 people with 50,000 in the surrounding area. Over 120 earthen mounds have been documented (Vilbig et al. 2020). Nowhere in the world do ancient burial mounds dominate the landscape as they do in Bahrain. Archaeological research has proved that these mounds were built in the Bronze Age by the inhabitants of the ancient realm of Dilmun, which managed trade between Mesopotamia, South Arabia, and India 4000 years ago. The most heavily mounded area is in northern Bahrain (Fig. 3.3), where there were are as many as 172,000 mounds (Lowe 1986). Their size varies, but the majority of them measure 4.5 to 9 m in diameter and 1 to 2 m high. Since the 1960s their number has been constantly reduced, due to the speed of economic development on the island; new roads and housing have expanded enormously with detrimental consequences. By 2006 there were perhaps no more than 20,000 left (Højlund 2007). Archaeological evidence shows that the burial sites were originally not constructed as mounds but as cylindrical low towers. They are now a World Heritage Site (https:// whc.unesco.org/en/list/1542/) (accessed 8 June 2023).

3.3 Tumuli Burial mounds are major landscape features in parts of Britain and Europe, where they are generally known as tumuli or barrows (https://historicengland.org.uk/imagesbooks/publications/iha-prehistoric-barrows-burial-mounds/) (accessed 8 June 2023). Tumuli are mounds of earth and/or stone of various shapes and sizes that are characteristic pre-historic earthwork monuments dating from about 5800 until 3400 years ago. Less intensive and intermittent construction and use of barrow mounds also occurred in later times up until about 1200 years ago (AD 800). Long barrows can generally be assigned to the earlier part of the time scale, being present from as early as 5,800 years ago. Externally, they comprise a large mound of material rarely more than about 50 m in length and up to 25 m in width, but sometimes in a slightly trapezoidal or oval form, often with one end wider and higher than the other. The earliest examples developed in Iberia and western France. The tradition then spread northwards, into the British Isles and then the Low Countries and southern Scandinavia. Across Europe, about 40,000 long barrows are known to survive from the Early Neolithic. Long barrows represent the oldest widespread tradition of using stone in construction. Round barrows have origins dating to before 5000 years ago. Their

56

3  Humanly-Made Landforms

Fig. 3.2  Google Earth image of Cahokia mounds, Illinois, USA. Scale bar is 70 m. Location: 38° 39′ 15.58ʺ N, 90° 3′ 49.49ʺ W

Fig. 3.3  Google Earth image of Dilmun mounds, northern Bahrain. Scale bar is 300 m. Location: 26° 8′ 58.47ʺ N, 50° 30′ 48.31ʺ E

3.5 Hillforts

57

Fig. 3.4  Google Earth image of clusters of barrows at Winterbourne Poor Lot, Dorset, southern England. Scale bar is 200 m. Location: 50° 42′ 53.28ʺ N, 2° 35′ 3.75ʺ W

size varies quite dramatically from examples of only 5 m or 6 m across to those that take on monumental proportions of over 50 m diameter and 6 m in height. The main period of round barrow construction occurred between about 4000 and 3500 years ago. Figure 3.4 shows barrows from Dorset in southern England. The largest Neolithic burial mound in Europe is Silbury Hill in southern England, which is 40 m high and 160 m in diameter (Bayliss et al. 2007). Tumuli associated with graves, as in Hungary, are known as kurgans (Dani 2020). Kurgans were built in the Ukrainian and Russian steppes, their use spreading with migration into southern, central, and northern Europe in the 3rd millennium BC.

BC). Over 80 causewayed enclosures are now known in the British Isles, and the majority are found in England south of the River Trent. More than 100 examples are recorded in France, and further sites are known from Scandinavia, Belgium, Germany, Italy, and Slovakia. Unlike hillforts, they were not primarily defensive structures, nor were they funerary monuments. Some appear to have been fortified, others to have been used for ceremonial, ritual, market, and social purposes, but their functions still remain obscure. Figure 3.5 shows a causewayed enclosure at The Trundle near Chichester in southern England.

3.4 Causewayed Enclosures

Hillforts are earthworks used as a fortified refuge or defended settlement (Hawkes 1931). There are more than 3000 in the British Isles (https://historicengland.org. uk/images-books/publications/iha-hillforts/) (accessed 8 June 2023). In spite of their name, not all are on hills and not all were necessarily built primarily for defence (Lock 2022). Some were built on the sites of Neolithic causewayed enclosures. In Europe they date to the Bronze and Iron Ages, though some were used in the post-Roman period and as sites of castles in medieval times. They consist of one or more ramparts and ditches. Maiden Castle in Dorset, southern England, is a notable

A  causewayed enclosure  is a type of large pre-historic earthwork common to the early Neolithic in Europe (Oswald et al. 2014) (https://historicengland.org.uk/ images-books/publications/iha-causewayed-enclosures/ heag200-causewayed-enclosures/) (accessed 8 June 2023). It is an enclosure marked out by ditches and banks, with a number of causeways crossing the ditches. Also known as ‘causewayed camps’ or ‘interrupted-ditch enclosures’, they represent the earliest known examples of the enclosure of open space. They date to the early Neolithic (4000–3300

3.5 Hillforts

58

3  Humanly-Made Landforms

Fig. 3.5  Google Earth image of Google Earth image of The Trundle causewayed enclosure, southern England. Scale bar is 100 m. Location: 50° 53′ 32.89ʺ N, 0° 45′ 13.10ʺ W

Fig. 3.6  Google Earth image of Maiden Castle hillfort, Dorset, southern England. Scale bar is 300 m. Location: 50° 41′ 43.91ʺ N, 2° 28′ 12.63ʺ W

59

3.6  Defensive Walls

example (Fig. 3.6). Covering 19 ha, and with some ramparts rising to more than 6 m, it is the largest hillfort in Britain. However, hillforts of broadly similar age are known from other parts of Europe, including the Iberian Peninsula. Some of those in the Ukraine, dating back to the seventh century BC, are so big that they have been termed ‘mega-hillforts’ and they can cover up to 8000 ha (Daragan 2020). Hillforts are known from outside Europe and occur, for example, in Fiji (Nunn et al. 2021).

3.6 Defensive Walls In addition to hillforts there are various other features that have been constructed for military purposes, including the Great Wall of China (Fig. 3.7). This was built from the seventh century onwards across the historical northern borders of ancient Chinese states and Imperial China as protection against  raiding nomadic groups  from the  Eurasian Steppe. The defensive capabilities of the Great Wall were enhanced by the construction of watchtowers, troop barracks, garrison stations, and signalling beacons. It is not a single ‘great wall’. The frontier walls built by different dynasties have multiple courses. Collectively, they stretch from Liaodong in the east to Lop Nor in the west and from the present-day Chinese-Russian border in the north to the Tao River in the south. In all this spans over 21,000 km.

There are impressive defensive walls in other parts of the world, including Iran (Nokandeh et al. 2006), with its Great Wall of Gorgan. This is 195 km long and 6–10 m wide and features over 30 fortresses spaced at intervals of between 10 and 50 km. It is surpassed only by the walls systems of the Great Wall of China as the longest single-segment building and the longest defensive wall in the world. It was built from c 420 to 530 AD (https://whc.unesco.org/en/tentativelists/6199/) (accessed 8 June 2023). Significant fortified walls were also built by the Romans. The Limes Germanicus were built in Germany, and they used either a natural boundary such as a river or they employed an earth bank and ditch with a wooden palisade and watchtowers at intervals. They were associated with a system of linked forts. Running from the northwest of the country to the Danube in the southeast, the total length was 568 km, and it included at least 60 forts and 900 watchtowers. In Hungary, the Csörsz Trench and ramparts were built in the Great Hungarian Plain. Other notable Roman defensive walls occurred in Britannia: the 118-km-long Hadrian’s Wall in northern England, which was built on the orders of the Emperor Hadrian in c. AD 122, and the Antonine Wall, a 60-km-long fortification in Scotland which was started by Emperor Antonius Pius in 142 AD as a defence against the ‘barbarians’ of the north (https:// www.worldheritagesite.org/list/Frontiers+of+the+Roman+ Empire) (accessed 8 June 2023).

Fig. 3.7  Google Earth image of the Great Wall of China. Scale bar is 300 m. Location: 40° 21′ 12.57ʺ N, 116° 0′ 28.14ʺ E

60

3  Humanly-Made Landforms

Fig. 3.8  Google Earth image of Broughton Castle moated settlement, Oxfordshire, England. Scale bar is 100 m. Location: 52° 2′ 26.06ʺ N, 1° 23′ 30.48ʺ W

3.7 Moated Settlements In many parts of the world there are settlements which are surrounded by moats and which therefore are called ‘moated settlements’. They occur in the British Isles, where many of them are of medieval age (Emery 1962). Figure 3.8 shows Broughton Castle, a medieval fortified manor house in Oxfordshire, England. Such moats may well have played a defensive role, but they may have had other functions. This is the case with the many moated settlements found in Thailand, where they date to the first millennium AD and consist of settlements surrounded by deep ditches and, sometimes, ramparts. These ditches may have been several metres deep and 25 to 40 m wide (Mudar 1999). Several potential functions for the earthworks have been theorised. Explanations have included not only defence, but also aquaculture, flood protection, symbolism or ritual, and water storage for domestic consumption as well as providing some mitigation for drought conditions (Scott and O’Riley 2017).

3.8 Qanat Qanat is Arabic for ‘conduit’ and is the most widely used term for the irrigation system among English speakers (see Sect. 2.3). They are underground, gently sloping tunnel

wells dug backwards into dryland alluvial fans until the water table is pierced (Wilkinson 1977). The water is then transmitted down the tunnels by gravity to be used for irrigation. Cities like Marrakech in Morocco very much depend on them (Faiz and Ruf 2010). They are characterised by vertical shafts which are constructed for disposal of spoil and to provide air to the miners who made them. These shafts are surrounded by accumulations of mined debris (Fig. 3.9). In Iran, some shafts are 100–120 m deep, and some of the tunnels run for as far as 40–50 km. It has often been maintained that these remarkable feats of hydraulic technology originated 2700–2500 years ago in Iran, northern Iraq, and eastern Turkey and subsequently spread to Arabia (Lightfoot 2000), Afghanistan, Armenia, Central Asia (e.g. the Turpan depression), northern India, Baluchistan, North Africa, Spain, Mexico, Chile, and Peru. However, some have argued for an Arabian origin (see Avni 2018). They have a number of other local names including falaj (Oman), foggara (North Africa), karez (Afghanistan), and khettara (Morocco). In some parts of the world they are still actively used, but elsewhere, partly because of the lowering of the water table by modern systems of pumping, they are in decline, as in Morocco (Lightfoot 1996a), Syria (Lightfoot 1996b), and Algeria (Remini et al. 2011). In Iran they have a World Heritage Site designation (https:// whc.unesco.org/en/list/1506/) (accessed 8 June 2023), and there are still over 30,000 qanats operating in that country,

3.9  Terraces and Lynchets

61

Fig. 3.9  Google Earth image of lines of qanat shafts near Erfoud, Morocco. Scale bar is 300 m. Location: 31° 25′ 53.46ʺ N, 4° 21′ 28.20ʺ W. They rise to the west of this image and provide water to the oasis of Erfoud, which lies to the east of this image

but many have been lost as a result of various anthropogenic activities (Maghrebi et al. 2022). Fears that climatic change is causing qanat (Aflaj) in Oman to dry out have been expressed (Al-Mamary 2021), as is also the case with the karez of Afghanistan (Azami et al. 2020).

3.9 Terraces and Lynchets Brown et al. (2021) have remarked that ‘Agricultural terraces are volumetrically the largest and most common landforms that humans have ever produced. They were created on all inhabited continents, and until the nineteenth century, were the only major systematic, and worldwide, anthropogenic alteration to slopes. Agricultural terraces are therefore probably the most obvious geomorphological marker of the ‘Anthropocene’…’ Brown et al. (2020) pointed out that agricultural terraces are common on sloping lands on all inhabited continents, from New Zealand to Norway, and range in altitude from sea level to over 2400 m in the French Alps and Peru. Indeed they saw them as the iconic landscapes of the Mediterranean, the Peruvian Andes, the Philippines, and the loess of north China. Some are of considerable antiquity, including those of Northumberland in northern England, which date back to the Early to Middle Bronze Age (Brown et al. 2023). Agricultural cultivation terraces have existed in Europe for at least 8000 years (Brown et al. 2020). Indeed, for

many centuries, valley floors, hillside, and stream channels have been terraced, notably in the New World’s arid and semi-arid highlands (Donkin 1979; Denevan 2001; Whitmore and Turner 2001), around the Mediterranean (Grove and Rackham 2001), in Iberia, on the mountains of South Asia and Arabia, and in sub-Saharan Africa (Grove and Sutton 1989), including northern Ethiopia (Nyssen et al. 2000). However, examples of terracing are also known from Belgium (Nyssen et al. 2014), France, and southern England, where in Roman and medieval times strip lynchets (rideaux) were produced by ploughing on steep slopes (Whittington 1962). They are at least in part a manifestation of deposition resulting from tillage erosion (Dabney and Vieira 2020) (see Sect. 9.4.3). In Asia, rice cultivation is often associated with extensive terraced hillsides, while some of the Pacific Islands such as Hawaii were terraced for taro cultivation (Allen 1971). In Europe many terraces are associated with vine and olive cultivation (Varotto et al. 2018). Figure 3.10 (top) shows some impressive terrace systems from the loess lands of China, while Fig. 3.10 (bottom) shows intricate terracing in Yunnan. Grove and Rackham (2001, p. 107) noted that traditional terraces had various forms: (1) step terraces which run parallel to the contours, (2) braided terraces, which zig-zag up slopes, (3) pocket terraces, which consist of crescentshaped walls producing root holds for individual crop trees, and (4) terraced fields in which one end is built up above the hillside and the other end is sunk in. Among the reasons

62

3  Humanly-Made Landforms

Fig. 3.10  Terracing. Top: Google Earth image of terracing in the loess terrain of Dingxi in China. Scale bar is 600 m. Location: 35° 35′ 18.71ʺ N, 104° 34′ 42.19ʺ E. Bottom: Google Earth image of traditional rice terracing in the mountains of Yuanyang, China. Scale bar is 90 m. Location: 23° 5′ 25.55ʺ N, 102° 48′ 34.81ʺ E

that Grove and Rackham (2001, p. 110) gave for why terraces have been built in the Mediterranean lands are: to redistribute sediment, increase soil depth for root penetration, make a gentler slope on which to cultivate, make a wall out of the stones which would otherwise interfere with

cultivation, increase absorption of water by the soil in big rainfall events, and control erosion. Some terrace structures have been built for harvesting and control of flood waters (Beckers et al. 2013) (see Sect. 9.3.4). Terraced wadis exist in Jordan, and evidence

3.11 Craters

of ancient floodwater farming, possibly beginning in the Neolithic and Bronze Age (McCorriston and Oches 2001), was found in the remarkable Wadi Faynan field system, adjacent to the Arava Valley (Crook 2009). Runoff/floodwater-based agricultural systems are also known in North Africa and southeast Spain (Giraldéz et al. 1988). In central and southern America large spreads of terraces were created in pre-European times by the Incas (Londoño 2008) and the Mayans (Fedick 1994) to retain soil and water and to facilitate cultivation on steep slopes (see Sect. 1.3). However, in Middle America, terracing suffered as a result of the Spanish conquest as the massive loss of the indigenous population reduced the labour required to maintain terraces, and Whitmore and Turner (2001) suggested that the use of terracing today is probably a pale shadow of that which existed before the Spanish arrived. In Peru (Inbar and Llerena 2000) migration to urban centres has led to many terracing systems being abandoned. This is also the case in some Mediterranean countries (Tarolli et al. 2014), where some have suffered from subsequent erosion by piping and other processes (Romero Díaz et al. 2007). Others have proved to be more durable (Solé-Benet et al. 2010). On the other hand, check dams have been installed in some Mediterranean areas since the 1970s to control debris flows, flooding, and soil erosion and to permit cultivation of vines, olives, and other crops in Spain (Boix-Fayos et al. 2007, 2008; Castillo et al. 2007) and in Italy (Lenzi 2002). The same is true of hillsides in Ethiopia (Nyssen et al. 2004) and Lesotho and Eswatini (see Sect. 9.7) in southern Africa.

3.10 Mine Spoil Heaps Waste material excavated from mines (see Sect. 2.7) is often dumped as spoil heaps at the ground surface. There are at least 2000 million tonnes of shale lying in pit heaps in the coalfields of Britain (Richardson 1976), and Price et al. (2011) notes that these are among the most significant anthropogenically produced landforms to be found in the UK. Wales alone has c 2500 abandoned coal spoil tips. The nature and distribution of different types of mining waste in England and Wales is discussed and mapped by the British Geological Survey (https://nora.nerc.ac.uk/ id/eprint/10083/1/OR10014.pdf) (accessed 31 May 2023). Some spoil heaps are impressively high, as in the former coal mining area of the Pas-de-Calais, northern France. This comprises a range of five cones, of which two reach 180 m, surpassing the highest natural peak in Flanders. Nyssen and Vermeersch (2010) describe the spoil heaps of Belgium and the erosional processes that have occurred on them. Another region of Europe with spoil heaps is the Donbas(s) in Ukraine, especially around the city of Donetsk, where

63

there are about 130 of them. Spoil heaps from gold mines dominate the landscape of Johannesburg in South Africa (Fig. 3.11 top), while in North Wales, at old mines such as that at Berwyn near Llangollen, there are huge quantities of slate waste fanning out across the landscape (Fig. 3.11 bottom). Spoil heaps are not only blemishes on the landscape, but they can also be hazardous, generating flash floods (Bedford et al. 2022), acid waste, and debris flows and landslides (Siddle et al. 1996).

3.11 Craters In times of war, craters are caused by bombs, shell impact, or the action of mines. Recently Hupy and Schaetzl (2006) and Hupy and Koehler (2012) have introduced the term ‘bombturbation’ to describe the process of land disturbance caused by explosive munitions. They suggested that in the twentieth century soil displacement by munitions amounted to ‘billions of cubic metres’. The First World War battlefields of Flanders were pocked by huge numbers of craters, and one, the Lochnagar Crater (Fig. 3.12 top), which was created by a massive mine explosion, had a diameter of 100 m and a depth of 30 m. Figure 3.12 (middle) shows some trenches and craters from a First World War battlefield at Beaumont Hamel in the Somme Department of northern France. Figure 3.12 (bottom) shows intensive cratering from the Second World War at Blanc Nez, also in northern France. What we see in the landscape today is but a fraction of the numbers of craters there were, for many have been filled in and otherwise obliterated, though this is less true of woodland areas that have not been subject to post-war cultivation (Waga and Fajer 2021). The First World War sites used to manufacture munitions, such as cordite, also produced distinctive landscapes, with multitudes of spaced out defensive walls and pits, as at Cliffe near Rochester, Kent, southeast England (Fig. 3.13), and Mossband near Carlisle in northern England. Some of these landscapes have now been eradicated or substantially changed as at Holton Heath, Dorset. Regrettably, as Putin’s war in Ukraine has shown (Fig. 3.14 top) our power to create such forms is increasing. Westing and Pfeiffer (1972) estimated that because of bombing in Indo-China between 1965 and 1971, 26 million craters, covering an area of 171,000 ha and involving a total displacement of no less than 2.6 billion m3 of earth, were produced (Fig. 3.13 bottom). In Laos, even after more than four decades, bomb craters remain discernible at densities that frequently exceed 200 km−2 and in some cases exceed 800 km−2 (Kiernan 2015). Craters are also a product of the nuclear age. Testing of nuclear bombs has produced a number of very large examples, most notably in the steppes of Kazakhstan (at c 50° 35ʹ N, 77° 50ʹ E), in the Thar Desert of India (at Pokhran,

64

3  Humanly-Made Landforms

Fig. 3.11  Top: Google Earth image of gold mine spoil heaps in Johannesburg, South Africa. Scale bar is 1 km. Location: 26° 13′ 52.99ʺ S, 27° 57′ 57.24ʺ E. Bottom: Google Earth image of slate mine waste at Berwyn, North Wales. Scale bar is 100 m. Location: 53° 0′ 21.92ʺ N, 3° 12′ 55.73ʺ W

c 27° 05′ N, 71° 45′ E), and in the Nevada Desert of the USA. The Sedan Crater in Nevada (Fig. 3.15) is the most spectacular example. It was created on 6 July 1962 by a 104 kilotonne of TNT underground nuclear explosion. The

device was buried 194 m below the desert floor in the Yucca Flat area. About 11 Mt of material was shifted, and the crater was 98 m deep and had a maximum diameter of 390 m. Clusters of small craters occur nearby. The consequences

3.13  Conclusion: Earth Moving Fig. 3.12  Google Earth image of the Cliffe munitions complex. Scale bar is 500 m. Location: 51° 28′ 51.78ʺ N, 0° 28′ 46.80ʺ E. Much of it was constructed and used in the First World War

65

66

3  Humanly-Made Landforms

Fig. 3.13  War craters. Top: Lochnagar crater, France. Scale bar is 70 m. Location: 50° 0′ 55.78ʺ N, 2° 41′ 51.14ʺ E. Middle: Google Earth image of First World War trenches and craters at Beaumont Hamel, France. Scale

bar is 70 m. Location: 50° 4′ 24.98ʺ N, 2° 38′ 57.00ʺ E. Bottom: Google Earth image of Second World War craters at Blanc Nez, northern France. Scale bar is 200 m. Location: 50° 55′ 29.21ʺ N, 1° 43′ 16.43ʺ E

of a French nuclear test in Algeria can still be seen at c 26o18’N, 0o03’W near Reggane. Not all nuclear test craters come from the dry regions referred to above. Others were produced on coral atolls such as Eniwetok and Bikini. The Castle Bravo crater on Bikini Atoll in the Marshall Islands is shown in Fig. 3.16. Detonated by the USA on 1 March 1954, the explosion left a crater 2000 m in diameter and 76 m in depth.

and industry. Broadly similar patterns and processes of loss of ponds have also been reported from China, Japan, and North America. The numbers of ponds in Great Britain fell from an estimated peak of 800,000 in the late nineteenth century to 200,000 by the mid-1980s, with loss rates accelerating after the Second World War up to the 1980s. However, beginning in the late 1980s, new ponds were created specifically for wildlife. Estimates of pond numbers in the British countryside showed that by 2007 there were 478,000.

3.12 Ponds Ponds and other depressions created by human excavations are another artificial landform type. While most are probably made for agricultural reasons there are some that are the result of resource exploitation. This is the case, for example, with some of the many depressions that dot the Norfolk landscape in eastern England. Here there are both large features produced by medieval peat diggers—the Broads—(Lambert et al. 1970) and pits produced to access marl for improving soil conditions (Prince 1962). However, as Jeffries (2012) has shown, the number of ponds in western European agricultural landscapes has declined over the twentieth century as land use practises changed, ponds have fallen in disuse or become silted up, and land has been developed for housing

3.13 Conclusion: Earth Moving In creating artificial landforms of the types outlined above, humans move large amounts of material which they either excavate or deposit. This was appreciated by Sherlock (1922) whose study covered a period when earth-moving equipment was still ill-developed. Nonetheless, on the basis of his calculations and detective work, he was able to state that ‘at the present time, in a densely peopled country like England, Man is many times more powerful, as an agent of denudation, than all the atmospheric denuding forces combined’ (p. 333). Price et al. (2011, p. 1056) estimated that in Great Britain over the last 200 years, ‘people have excavated, moved and built up the equivalent of at least six times the

3.13  Conclusion: Earth Moving

67

Fig. 3.14  Google Earth images of craters produced by shelling and bombing. Top: Mariupol, Ukraine, in 2023. Scale bar is 80 m. Location: 47° 6′ 27.15ʺ N, 37° 34′ 25.39ʺ E. Bottom: Bomb craters from the war in Indo-China pepper an agricultural landscape. Scale bar is 80 m. Location: 19° 15′ 15.82ʺ N, 103° 6′ 11.24ʺ E

68

3  Humanly-Made Landforms

Fig. 3.15  Google Earth images of craters produced by underground nuclear tests in Nevada, USA. Top: Sedan Crater. Scale bar is 400 m. Bottom: Clusters of craters. Scale bar is 2 km. Location: 37° 6′ 57.63ʺ N, 116° 2′ 52.02ʺ W

References

69

Fig. 3.16  Google Earth image of the Castle Bravo crater on Bikini Atoll, Pacific Ocean. Scale bar is 2 km. Location: 11° 41′ 42.43ʺ N, 165° 16′ 15.99ʺ E

volume of Ben Nevis’. Hooke (1994) produced some data on the significance of deliberate human earth-moving actions in the USA and globally. He calculated that deliberate human earth moving causes 30 billion tonnes to be moved per year on a global basis. Douglas and Lawson (2000) gave a rather larger figure of 57 billion tonnes per year. Cooper et al. (2018) have gone so far to suggest that humans are ‘the most significant global geomorphological driving force in the twentieth century’. However, a word of caution is necessary. Their conclusion is based on a comparison of the quantity of earth moving associated with aggregate and mineral mining in comparison with the amount of material transported in the world’s rivers. A great deal of geomorphological work is achieved by other natural processes, including glacial, coastal, biological, and aeolian ones.

References Allen B (1971) Wet-field taro terraces on Mangaia, Cook Islands. J Polynesian Soc 80:371–378 Al-Mamary SA (2021) Effect of climate change on Aflaj in the sultanate of Oman. In: Towards a sustainable water future: proceedings of Oman’s international conference on water engineering and management of water resources. ICE Publishing, pp 131–150 Azami A, Sagin J, Sadat SH, Hejran H (2020) Sustainable irrigation: Karez system in Afghanistan. Central Asian J Water Res 6(2):65–86

Bayliss A, McAvoy F, Whittle A (2007) The world recreated: redating Silbury Hill in its monumental landscape. Antiquity 81:26–53 Beckers B, Berking J, Schütt B (2013) Ancient water harvesting methods in the drylands of the Mediterranean and Western Asia. J Ancient Studies 2:145–164 Bedford MD, Foster PJ, Gibson MJ, Chen AS (2022) Modelling flooding due to runoff from spoil heaps during heavy rainfall. Mining Technol 131(4):239–248 Blanco-González A, Kienlin TL (eds) (2020) Current approaches to tells in the prehistoric old world: a cross-cultural comparison from early neolithic to the iron age. Oxbow Books, Oxford, p 224 Boix-Fayos C, Barberá GG, López-Bermúdez F, Castillo VM (2007) Effects of check dams, reforestation and land-use changes on river channel morphology: case study of the Rogativa catchment (Murcia, Spain). Geomorphology 91:103–123 Boix‐Fayos C, de Vente J, Martínez‐Mena M, Barberá GG, Castillo V (2008) The impact of land use change andcheck‐dams on catchment sediment yield. Hydrol Proc 22:4922–4935 Brown A, Walsh K, Fallu D, Cucchiaro S, Tarolli P (2020) European agricultural terraces and lynchets: from archaeological theory to heritage management. World Archaeol 52(4):566–588 Brown AG et al (2021) Ending the Cinderella status of terraces and lynchets in Europe: the geomorphology of agricultural terraces and implications for ecosystem services and climate adaptation. Geomorphology 379:107579 Brown AG et al (2023) Early to Middle Bronze Age agricultural terraces in north-east England: morphology, dating and cultural implications. Antiquity. https://doi.org/10.15184/aqy.2023.1 Castillo VM, Mosch WM, Garcia CC, Barberá GG, Cano JA, LópezBermúdez F (2007) Effectiveness and geomorphological impacts of check dams for soil erosion control in a semiarid Mediterranean catchment: El Cárcavo (Murcia, Spain). CATENA 70:416–427

70 Cooper AH, Brown TJ, Price SJ, Ford JR, Waters CN (2018) Humans are the most significant global geomorphological driving force of the 21st century. Anthrop Rev 5(3):222–229 Crook D (2009) Hydrology of the combination irrigation system in the Wadi Faynan, Jordan. J Archaeol Sci 36(10):2427–2436 Dabney SM, Vieira DA (2020) Tillage erosion: terrace formation. In: Fath BD, Jorgensen SE (eds) Managing soils and terrestrial systems. CRC Press, Baton Roca, pp 543–550 Dani J (2020) Kurgans and their builders. The Great Hungarian Plain at the dawn of the bronze age. Hungarian Archaeol 9(2):1–20 Daragan M (2020) About appearance of mega-hillforts in the Ukrainian forest-steppe in the early Scythian time: the search for an explanatory model. Tyragetia 14(1):117–139 Denevan WM (1992) The pristine myth: the landscape of the Americas in 1492. Ann Ass Am Geogr 82:369–385 Denevan WM (2001) Cultivated landscapes of native Amazonia and the Andes. Oxford University Press, Oxford, p 426 Donkin RA (1979) Agricultural terracing in the aboriginal New World. University of Arizona Press, Tucson, p 196 Douglas I, Lawson N (2000) The human dimensions of geomorphological work in Britain. J Industr Ecol 4(2):9–33 Elfadaly A et al (2019) Discovering potential settlement areas around archaeological tells using the integration between historic topographic maps, optical, and radar data in the northern Nile Delta, Egypt. Remote Sens 11(24):3039 Emery FV (1962) Moated settlements in England. Geography 47:378–388 Faiz ME, Ruf T (2010) An introduction to the Khettara in Morocco: two contrasting cases. In: Schneier-Madanes G, Courel MF (eds) Water and sustainability in arid regions. Springer, Dordrecht, pp 151–163 Fedick SL (1994) Ancient Maya agricultural terracing in the upper Belize River area. Ancient Mesoam 5:107–127 Giraldéz JV, Ayuso JL, Garcia A, Lopez JG, Roldán J (1988) Water harvesting strategies in the semiarid climate of southeastern Spain. Agric Water Manag 14:253–263 Goudie AS (2022) Introduction: geomorphology at the start of the twenty-first century. In: Barbosa dos Santos G, Fernandes Felippe M, Marques Neto R (eds) Geomorphology of Brazil: complexity, interscale and landscape. Springer, Cham. https://doi. org/10.1007/978-3-031-05178-4_1 Goudie AS, Viles HA (2016) Geomorphology in the Anthropocene. Cambridge University Press, Cambridge, p 380 Grove AT, Rackham O (2001) The nature of Mediterranean Europe: an ecological history. Yale University Press, New Haven and London, p 390 Grove AT, Sutton JEG (1989) Agricultural terracing south of the Sahara. Azania 24:113–122 Hall BA (1994) Formation processes of large earthen residential mounds in La Mixtequilla, Veracruz, Mexico. Latin Am Antiquity 5:31–50 Hawkes C (1931) Hill-forts. Antiquity 5(17):60–97 Højlund F (2007) The burial mounds of Bahrain. Social complexity in early Dilmun. Jutland Archaeol Soc Publ 58 Hooke RL (1994) On The efficacy of humans as geologic agents. GSA Today 4:217–224 Hupy JP, Koehler T (2012) Modern warfare as a significant form of zoogeomorphic disturbance upon the landscape. Geomorphology 157:169–182 Hupy JP, Schaetzl RJ (2006) Introducing “bombturbation”, a singular type of soil disturbance and mixing. Soil Sci 171:823–836 Inbar M, Llerena CA (2000) Erosion processes in high mountain agricultural terraces in Peru. Mountain Res Develop 20:72–79 Jeffries MJ (2012) Ponds and the importance of their history: an audit of pond numbers, turnover and the relationship between the origins of ponds and their contemporary plant communities in south-east Northumberland, UK. Hydrobiologia 689:11–21

3  Humanly-Made Landforms Kiernan K (2015) Nature, severity and persistence of geomorphological damage caused by armed conflict. Land Degrad Develop 26:380–396 Lambert JM, Jennings JN, Smith CT, Green C, Hutchinson JN (1970) The making of the broads: a reconsideration of their origin in the light of new evidence. R Geogr Soc Res Ser 3:15 Lenzi MA (2002) Stream bed stabilization using boulder check dams that mimic step-pool morphology features in Northern Italy. Geomorphology 45:243–260 Lightfoot DR (1996a) Moroccan khettara: traditional irrigation and progressive desiccation XE “Desiccation.” Geoforum 27:261–273 Lightfoot DR (1996b) Syrian qanat Romani: history, ecology, abandonment. J Arid Environ 33:321–326 Lightfoot DR (2000) The origin and diffusion of qanats in Arabia: new evidence from the northern and southernpeninsula. Geogr J 166(3):215–226 Lock G (2022) Atlas of the hillforts of Britain and Ireland. Edinburgh University Press, Edinburgh, p 496 Londoño AC (2008) Pattern and rate of erosion inferred from Inca agricultural terraces in arid southern Peru. Geomorphology 99:13–25 Lowe A (1986) Bronze age burial mounds on Bahrain. Iraq 48:73–84 Lubos CCM, Dreibrodt S, Nelle O, Klamm M, Friederich S, Meller H, Bork HR (2011) A multi-layered prehistoric settlement structure (tell?) at Niederröblingen, Germany and its implications. J Archaeol Sci 38:1101–1110 Macdonald KC (1997) More forgotten tells of Mali: an archaeologist’s journey from here to Timbuktu. Archaeol Int 1:40–42 Maghrebi M et al (2022) Anthropogenic decline of ancient, sustainable water systems: qanats. Groundwater 61:139–146 Maghsoudi M, Simpson IA, Kourampas N, Nashli HF (2014) Archaeological sediments from settlement mounds of the Sagzabad cluster, central Iran: human-induced deposition on an arid alluvial plain. Quat Int 324:67–83 McCorriston J, Oches E (2001) Two early Holocene check dams from southern Arabia. Antiquity 75:675–676 Menze BH, Ur JA (2012) Mapping patterns of long-term settlement in northern Mesopotamia at a large scale. Proc Nat Acad Sci 109:E778-787 Mudar KM (1999) How many Dvaravati kingdoms? Locational analysis of first millennium AD moated settlements in central Thailand. J Anthropo Archaeol 18(1):1–28 Nokandeh J et al (2006) Linear barriers of northern Iran: the great wall of Gorgan and the wall of Tammishe. Iran 44(1):121–173 Nunn PD et al (2021) A Koronivalu kei Bua: Hillforts in Bua Province (Fiji), their chronology, associations, and potential significance. J Island Coast Archaeol 16(2–4):342–370 Nyssen J, Vermeersch D (2010) Slope aspect affects geomorphic dynamics of coal mining spoil heaps in Belgium. Geomorphology 123:109–121 Nyssen J, Veyret-Picot M, Poesen J, Moeyersons J, Haile M, Deckers J, Govers G (2004) The effectiveness of loose rock check dams for gully control in Tigray, northern Ethiopia. Soil Use Manag 20:55–64 Nyssen J, Debever M, Poesen J, Deckers J (2014) Lynchets in eastern Belgium—a geomorphic feature resulting from non-mechanised crop farming. CATENA 121:164–175 Oswald A, Dyer C, Barber M (2014) The creation of monuments: neolithic causewayed enclosures in the British Isles. Liverpool University Press, Liverpool, p 200 Peet SD (1891) The Great Cahokia mound. Am Antiquarian Orient J 13(1):1–31 Price SJ, Ford JR, Cooper AH, Neal C (2011) Humans as major geological and geomorphological agents in the Anthropocene: the significance of artificial ground in Great Britain. Phil Trans Roy Soc A 369:1056–1084

References Prince HC (1962) Pits and ponds in Norfolk. Erdkunde 1:10–31 Remini B, Achour B, Albergel J (2011) Timimoun’s foggara (Algeria): an heritage in danger. Arab J Geosci 4:495–506 Richardson JA (1976) Pit heap into pasture. In: Lenihan J, Fletcher WW (eds) Reclamation. Blackie, Glasgow, pp 60–93 Romero Díaz A, Marin Sanleandro P, Sanchez Soriano A, Belmonte Serrato F, Faulkner H (2007) The causes of piping in a set of abandoned agricultural terraces in southeast Spain. CATENA 69:282–293 Scott G, O’Reilly D (2017) A re-appraisal of the spatial distribution of single and multi-moat prehistoric sites in Northeast Thailand. Archaeol Res Asia 11:69–76 Sherlock RL (1922) Man as a geological agent: an account of his action on inanimate nature. Witherby, London, p 400 Siddle HJ, Wright MD, Hutchinson JN (1996) Rapid failures of colliery spoil heaps in the South Wales Coalfield. Q J Eng Geol Hydrogeol 29(2):103–132 Solé-Benet A, Lázaro R, Domingo F, Cantón Y, Puigdefábregas J (2010) Why most agricultural terraces in steep slopes in semiarid SE Spain remain well preserved since their abandonment 50 years go? Pirineos 165:215–235 Szabó J, Dávid L, Lóczy D (eds) (2010) Anthropogenic geomorphology: a guide to man-made landforms. Springer, Heidelberg, p 260

71 Tarolli P, Preti F, Romano N (2014) Terraced landscapes: from an old best practice to a potential hazard for soil degradation due to land abandonment. Anthropocene 6:10–25 Tarolli P, Cao W, Sofia G, Evans D, Ellis EC (2019) From features to fingerprints: a general diagnostic framework for anthropogenic geomorphology. Progr Phys Geogr 43(1):95–128 Varotto M, Bonardi L, Tarolli P (eds) (2018) World terraced landscapes: history, environment, quality of life. Springer, Cham, p 601 Vilbig JM, Sagan V, Bodine C (2020) Archaeological surveying with airborne LiDAR and UAV photogrammetry: a comparative analysis at Cahokia Mounds. J Archaeol Sci: Reports 33:102509 Waga JM, Fajer M (2021) The heritage of the Second World War: bombing in the forests and wetlands of the Koźle Basin. Antiquity 95:417–434 Westing A, Pfeiffer EW (1972) The cratering of Indochina. Sci Am 226(5):21–29 Whitmore TM, Turner BL (2001) Cultivated landscapes of Middle America on the eve of conquest. Oxford Univ Press, Oxford, p 311 Whittington G (1962) The distribution of strip lynchets. Trans Inst Brit Geogr 31:115–130 Wilkinson JC (1977) Water and tribal settlement in South-East Arabia: a study of the Aflāj of Oman. Clarendon Press, Oxford, p 276

4

Rivers

Abstract

Major alterations have been caused to river systems by human activities. In this chapter the following are considered: dam and reservoir construction, interbasin water transfers, channelisation, changes in river channels as a result of land use and land cover changes, sedimentation of floodplains, deltas, and changes in flooding regimes.

Keywords

Channelisation · Dams · Deltas · Sedimentation · Interbasin water transfers · Runoff

4.1 Introduction Changes to fluvial systems are some of the most evident that have occurred in the Anthropocene. For example, evidence of human dominance is more widespread in fluvial and coastal records than in aeolian and cryospheric ones. To a certain extent this is scale dependent, and as Brown et al. (2017, p. 71) wrote: …..it is clear that, with the exception of heavily-modified catchments, the relative magnitude of human impact on the fluvial process domain is dependent on catchment scale, tectonic activity and relief, and susceptibility to erosion. The anthropogenic signal may be more clearly defined in small- to medium-sized catchments draining, for example, highly erodible loessic landscapes. The signal may be less clear in large catchments such as the Ganges and Brahmaputra that are subject to active tectonic activity and high sediment supply, and characterized by accommodation space for medium-term sediment storage, subsequent erosion of which can nourish sediment flux for millennia

4.2 Dams and Barriers The construction of dams dates back to prehistoric times, particularly in Mesopotamia and the Middle East. The earliest known dam is the Jawa Dam in Jordan. It was comprised of an originally 9 m high and 1 m wide stone wall, supported by a 50 m wide earthen rampart. The structure is dated to c 5000 years ago. The Ancient Egyptians built a dam at Wadi Al-Garawi, about 25 km south of Cairo. This was 102 m long at its base. It was built around 4800 years ago as a diversion dam for flood control. In Yemen, a great dam was built at Ma’rib. The initial date of the first construction lies somewhere between 1750 and 1700 BC. It was composed of packed earth, triangular in cross section, and 580 m in length and 4 m high. Around 500 BC, its height was increased to 7 m. In Classical Greece, during the Mycenaean Era (1900–1100 BC), large dams were built in the Peloponnese. One was erected around 1200 BC across the Lakissa River to protect the town of Tyrins from flooding (Angelakis et al. 2020). The Romans were also great dam builders, and many examples are known from Libya (Vita-Finzi 1961). Other early dams and reservoirs were developed inter alia in Sri Lanka, Cambodia, and China. For example, the Liangzhu hydraulic system in the Yangtze Delta used dams that were constructed c 5100 years ago (Liu et al. 2017). In the modern era, the construction of large dams has increased markedly, especially between 1945 and the early 1970s. It has been estimated more than 45,000 large dams (i.e. more than 15 m high) around the world. They have become increasingly large (Table 4.1). Thus in the 1930s the Hoover or Boulder Dam in the USA (221 m high) was by far the tallest in the world and it impounded the biggest reservoir, Lake Mead. By the 2000s it was exceeded in

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 A. Goudie, Landscapes of the Anthropocene with Google Earth, https://doi.org/10.1007/978-3-031-45385-4_4

73

74

4 Rivers

Table 4.1  World’s largest reservoirs (from data provided by the International Commission on Large Dams (www.icold-cigb.org) (Accessed 8th June 2023)) Reservoirs with an area > 5000 km2

Reservoirs with a volume > 100 km3

Volta, Ghana

8482

Kariba, Zambia/ Zimbabwe

181

Smallwood, Canada

6527

Bratsk, Russia

169

Kuybyshev, Russia

6450

Nasser, Egypt

162

Kariba, Zambia/Zimbabwe

5580

Volta, Ghana

150

Bukhtarma, Kazakhstan

5490

Manicouagan, Canada 142

Bratsk, Russia

5426

Guri, Venezuela

Nasser, Egypt

5248

135

height by at least 29 others, and four of these impounded reservoirs (Kariba, Bratsk, Nasser and Volta) with more than four times the volume of Lake Mead. The tallest dam, which is 335 m high, is the Rogun Dam in Tajikistan. Although there are a number of multipurpose dams, most dams have a single-purpose. Among the single-purpose dams, 48% are for irrigation, 17% for hydropower (production of electricity), 13% for water supply, 10% for flood control, 5% for recreation and less than 1% for navigation and fish farming (http://www.icold-cigb.org/GB/world_register/general_synthesis.asp) (Accessed 2nd March, 2017). Currently, more than 50% of the world’s river flow crosses one or more dams before reaching the oceans. In China reservoir construction has been massive in recent decades (Yang and Lu 2014). By 2013, 98,000 reservoirs had been built. Large dams are the main cause of fluvial sediment being sequestered upstream (see Sect. 4.10), leading to a global decline of 18% in sediment delivery to the coastal ocean compared with pre-human times (Syvitski et al. 2020). Of the 58,519 large dams registered in 2017, 1.4% were built before 1850, and 10% were built between 1850 and 1950. 95.7% of the world’s total reservoir capacity has been emplaced since 1950. Large dams (> 15 m in elevation) are the main cause of fluvial sediment being sequestered upstream, leading to a global decline of 18% in sediment delivery to the coastal ocean compared with pre-human times. Most dams achieve their aim, which is to regulate river discharge. Millions of people depend upon them. However, they have numerous environmental consequences that may or may not have been anticipated. These include subsidence, earthquake triggering, the transmission and expansion in the range of organisms, inhibition of fish migration, the build-up of waterlogging and soil salinity, changes in groundwater levels creating slope instability, and the modification of sources of sediment and sand transport paths (Draut 2012). Sediment deposition in reservoirs has various

possible consequences, including a reduction in flooddeposited nutrients on fields, less nutrients for fish offshore, accelerated erosion of deltas and shorelines, and accelerated riverbed erosion since less sediment is available to cause bed aggradation. The last process is called ‘clear-water erosion’. Dam construction causes river fragmentation and this, along with other human modifications, changes the natural connectivity within and among river systems (Grill et al. 2015; Poeppl et al. 2015). Many dams are small structures. This is the case in the USA where there are some 80,000 dams. Some river landscapes in the world are dominated by such small dams, canals and reservoirs. Probably the most striking example of this is the ‘tank’ landscape of south-east India where myriads of little streams and areas of overland flow have been dammed by small earth structures, most of which have a submerged area of less than 5 ha, to give what Spate and Learmonth (1967, 778) likened to ‘a surface of vast overlapping fish-scales’ (Fig. 4.1). This is a type of water harvesting in which ponds are closed by crescent-shaped earth dams called bunds that extend across the natural drainage flow and are supplied by (i) in situ rainfall; and (ii) seasonal flood runoff (Gunnell and Krishnamurthy 2003). The irrigated area supplied by tanks, typically varies between 1.5 and 50 ha. In India as a whole the number of tanks and ponds is reported to be between 0.2 and 0.35 million (Reddy et al. 2018). Many of them have fallen out of use in recent decades as a result of their replacement as sources of irrigation water by groundwater wells, and because of siltation. Around 18,000 of these tanks, locally called wewa, are also present in the dry zone of neighbouring north-eastern Sri Lanka. Because of the problems posed by dams, there have been many attempts recently to remove them as part of ‘river restoration’ or because they have become unsafe (Ibisate et al. 2016; Foley et al. 2017). Most of the dams involved have been just a few metres high, though an Australian example was 15 m high (Neave et al. 2009). In New England, 127 dams were removed between ca. 1990 and 2013. These ranged in size, with the largest number (30%) ranging between 2 and 4 m high, but with 22% between 4 and 6 m high (Magilligan et al. 2016). Among the consequences of dam removal are incision into the sedimentary fill that had accumulated in the reservoir behind the dam, migration of a knickpoint upstream, deposition of liberated sediment and the formation of bars and the like downstream (Major et al. 2012). This very much depends on the nature and erodibility of the fill and the river’s regime. Some rivers appear to remove their fill rapidly and almost entirely, while others do not. Warrick et al. (2019) reported on the effects of dam removal on sediment supply and coast accretion following the removal of the Elwha and Glines Canyon Dams from the Elwha River, Washington, USA. Built in 1912 and

4.3  Interbasin Water Transfers

75

Fig. 4.1  Google Earth image of the tank landscape of South India. Scale bar is 2 km. Location: 9° 43′ 45.90ʺ N, 78° 40′ 54.37ʺ E

1927, these two hydroelectric dams were originally 32 and 64 m in height. The removal of these large dams is the largest dam removal project so far, because it involved the tallest dam intentionally removed and the greatest sediment release. The deconstruction of the two dams caused ~ 20 Mt of increased sediment supply to the river during the first five years of the project (2011–2016). This huge new supply of sediment—equivalent to two-thirds of the total sediment stored in the reservoirs—increased sediment fluxes in the Elwha River by approximately two orders of magnitude, leading to coastal sediment replenishment. However, a study of the Carmel dam removal in California by East et al. (2023) showed a much more muted response to that of the Elwha, partly as a result of sediment management on the floor of the former reservoir. Dams are not the only barriers placed across rivers. There may also be weirs, ramps, culverts, sluices, locks and fords. The study by Jones et al. (2019a, b) indicated that 97% of the river network in Great Britain is fragmented and that less than 1% of the catchments are free of artificial barriers. There is at least one artificial barrier for every 1.5 km of stream in Great Britain. A similar picture was given for Europe by Belletti et al. (2020). Their work indicated that there are on average 0.74 barriers per km of river length, ranging from 0.005 barriers per km for Montenegro to 19.44 barriers per km for the Netherlands, with a median distance between adjacent barriers for all countries of

108 m. The highest barrier densities were found in Central Europe and correspond with densely populated areas, intense use of water and high road density; in contrast, the lowest barrier densities tend to occur in the most remote, sparsely populated alpine areas (e.g. Scandinavia, Iceland, and Scotland). Very few major rivers are now free-flowing rivers (FFRs). Grill et al. (2019) estimated that 64% of the world’s longest rivers (> 1000 km) are no longer free-flowing. Long FFRs (> 500 km) are largely absent from the mainland USA, Mexico, Europe, and the Middle East, as well as parts of India, southern Africa, southern South America, China and much of Southeast Asia and southern Australia. The remaining long FFRs are restricted to the northern parts of North America and Eurasia, the Amazon and Orinoco Basins in South America, the Congo Basin in Africa, and to only a few areas in Southeast Asia, including the Irrawaddy and Salween Basins.

4.3 Interbasin Water Transfers Deliberate modification of a river regime can be achieved by long-distance interbasin water transfers (IBWT) (Shiklomanov 1985; Ghassemi and White 2007). The total volume of water in the various transfer systems in operation and under construction on a global scale is about 300 km3 a

76

year, with the largest countries in terms of volume of transfers being Canada, the former Soviet Union, the USA, and India. There are also major schemes in southern Africa (Snaddon et al. 1998). China’s South–North Water Transfer Project (SNWTP) is currently the world’s largest interbasin transfer scheme, connecting four major river basins. Its purpose is to address the imbalance in the distribution of China’s water resources, by transferring water from the wetter south to the drier north via the Yangtze River to the Hai, Huai, and Yellow river basins (Rogers et al. 2020). In the USA there are 2161 man-made waterways linking different river systems, with about half of them in Florida, Texas, and North Carolina (Dickson and Dzombak 2019; Siddik et al. 2023). Water transfer projects have been employed for over 4000 years. Two early examples include the canal to transfer water from the Tigris to the Euphrates constructed in 2500 BC, and the Lingqu Canal connecting the Yangtze and Pearl River basins built in 214 BC. However, large-scale development occurred the nineteenth century, with further development in the twentieth century. The number of IBWT projects constructed peaked in the 1970s (Sinha et al., 2020). The predominant aim of these projects has been to secure water supplies for areas affected by water stress by transferring water from catchments of relative water abundance. Municipal usage is by far the most commonly stated primary driver for schemes, with irrigation coming second.

4 Rivers

In countries such as Canada and Norway, which have comparatively high rainfalls, IBWTs are primarily used to augment the power generation potential of hydroelectric schemes. There are various environmental consequences of IBWT schemes (Rollason et al. 2021). The removal of flow from donor rivers can have major impacts on natural flows leading to changes in downstream morphology, drying up of wetlands, and promoting delta retreat, which in turn can lead to sea-water incursion. In recipient basins, enhanced flows can promote wasteful water use, particularly in irrigated areas, resulting in waterlogging and enhanced salinisation. The linking of two previously independent basins can lead to invasive species passing through the transfer, alter the distribution of fish species, as well as facilitate the transfer of pollutants. One of the most spectacular results of IBWT schemes is the desiccation of lakes, such as the Aral Sea and Owens Lake in California (see Sect. 7.3). Built between 1908 and 1913, the Los Angeles Aqueduct tapped into the waters of the Owens River and delivered water over 370 km south to Los Angeles. Figure 4.2 shows this aqueduct next to the dried up bed of the Owens Lake, which had, before its diversion into the canal, been fed by the Owens River. This dried-up bed is now a major source of dust and of miscellaneous hazardous chemicals.

Fig. 4.2  Google Earth image of The Los Angeles aqueduct and the dried-up Owens Lake in California. Scale bar is 1 km. Location: 36° 26′ 40.82ʺ N, 118° 2′ 7.97ʺ W

4.4  Channelisation and Straightening

4.4 Channelisation and Straightening Multiple factors are involved in the transformation of river channels by humans (see Table 4.2). One direct means of river manipulation is channelisation. This form of ‘hard engineering’ involves the construction of embankments, dykes, levées and floodwalls to confine floodwaters, reduce channel migration, and to improve the ability of channels to transmit floods by enlarging their capacity through straightening, widening, deepening or smoothing. Many rivers have in effect been strangled (Brierley et al. 2023). To improve navigation and flood control humans have deliberately straightened many river channels (see Fig. 4.3). Elimination of meanders contributes to flood control in two ways. First, it eliminates some overbank floods on

Table 4.2  Some causes of river transformation

77

the outside of curves, against which the swiftest current is thrown and where the water surface rises highest. Second, and more importantly, the resultant shortened course increases both the gradient and the flow velocity, and the floodwaters erode and deepen the channel, thereby increasing its flood capacity. It was for flood control that in the early 1930s a programme of channel cut-offs was initiated along the Mississippi River. By 1940 it had lowered flood stages by as much as 4 m at Arkansas City, Arkansas, and by 1950 the length of the river between Memphis, Tennessee and Baton Rouge, Louisiana (600 km down the valley) had been reduced by 270 km as a result of 16 cut-offs. Many channels have been constrained by the emplacement of riprap (rock armour) (Reid and Church 2015), while others, like the Los Angeles River in Los Angeles, have been put in a corset of concrete.

Anthropogenic climate changes Biogeomorphological changes (e.g. changes in woody debris and beaver dams, invasive plants) Dam and reservoir construction Dam removal and river restoration Flood relief channel construction Interbasin water transfers Land cover and land use changes (e.g. deforestation, reforestation, urbanisation) Miscellaneous engineering works (e.g. channelisation, straightening, levee construction)

Fig. 4.3  Google Earth image of the straightening of a portion of the River Rhine in Germany. Scale bar is 6 km. Location: 49° 14′ 22.64ʺ N, 8° 24′ 16.30ʺ E

78

Deliberate channel straightening leads to sequential channel adjustment both within and downstream from straightened reaches, and the types of adjustment vary according to such factors as stream gradients and sediment types. Brookes (1987) recognised five types of change within the straightened reaches (types W1 to W5) and two types of change downstream (types D1 and D2): Type W1 is degradation of the channel bed, which results from the fact that straightening increases the slope by providing a shorter channel path. This in turn increases its sediment transport capability. Type W2 is the development of an armoured layer on the channel bed by the more efficient removal of fine materials as a result of the increased sediment transport capability referred to above. Type W3 is the development of a sinuous thalweg in streams which are not only straightened but which are also widened beyond the width of the natural channel. Type W4 is the recovery of sinuosity as a result of bank erosion in channels with high slope gradients. Type W5 is the development of a sinuous course by deposition in streams with a high sediment load and a relatively low valley gradient. Types D1 and D2 result from deposition downstream as the stream tries to even out its gradient, the deposition occurring as a general raising of the bed level, or as a series of accentuated point bar deposits.

4 Rivers

4.5 Levees and Dykes Often associated with river straightening is the construction of levees or dykes. The main purpose of such artificial levees is to prevent flooding of the adjoining countryside and to slow natural course changes in a waterway to provide reliable shipping lanes for maritime commerce; they also confine the flow of the river, resulting in higher and faster water flow. Levees have some antiquity, and some of the earliest were constructed in the Indus Valley by the Harappan civilisation over 4000 years ago. Levees were also constructed over 3,000 years ago along the Nile. The Mesopotamian civilisations and ancient China also built large levee systems. Artificial levee construction began in the U.S. in the early 1700s by landowners living alongside the lower Mississippi River. Today, The Mississippi levee system represents one of the largest such systems found anywhere in the world (see Fig. 4.4). It comprises over 5600 km of levees extending some 1000 km from Cape Girardeau in Missouri, to the Mississippi delta in Louisiana. Some Mississippi levees are as high as 15 m. The total length of artificial levees in the U.S. is unknown but estimates that range between 48,000 and 167,000 km have been given, but these figures may well be too low (Knox et al. 2022a). Their ecological consequences are discussed by Knox et al. (2022b). In addition to levees of an essentially channel-parallel nature, some rivers are channelised through the

Fig. 4.4  Google Earth image of levees on the Mississippi River, USA. Scale bar is 1 km. Location: 29° 58′ 14.54ʺ N, 90° 15′ 1.17ʺ W

4.6  Flood Relief Channels or Bypasses

construction of dykes that are constructed perpendicularly to the channel, as in the Rhône valley of France (Seignemartin et al. 2023).

4.6 Flood Relief Channels or Bypasses Flood relief channels are one means of reducing flood risk. Flood diversions take water from a flooding river to reduce stage in the main river, diverting excess flow to another location. Flood bypasses are a specific type of flood diversion that route floodwaters around reaches where the consequences of flooding are particularly undesirable. Serra-Llobet et al. (2022, p. 20) proposed a classification that distinguished among distinct types of diversions, such as bypasses that route floodwaters around constrained reaches where flooding is to be avoided (e.g. cities) and return floodwaters to the river downstream, distributaries that divert water from the river and discharge directly to the sea, backwaters that function like shock absorbers (storing floodwaters during the flood peak, releasing the water gradually back into the river afterward), and interbasin transfers of floodwaters.

The term ‘flood bypass’ refers to a type of flood diversion in which the flow follows an alternative path before it rejoins

79

the main river, be it a tunnel, an engineered channel, or a broad swath of floodplain. Some bypasses are wet all year round, while some are dry for most of the year, when they can serve wildlife, agriculture, or recreation. In the UK the Maidenhead, Windsor and Eton Flood Alleviation Scheme is an engineered bypass channel (known as the Jubilee River) constructed to mitigate the floods of the River Thames in the three named towns and nearby villages. The scheme consists mainly of a 11.6 km long, earthen trapezoidal channel, with a bottom width of c 30 m and a top width of 45 m. It diverts river water from the Thames upstream of Maidenhead, running parallel and to the north of the river, and rejoins the Thames downstream of Windsor. The scheme reduces the risk of flooding to approximately 3,000 properties in Maidenhead, Windsor, Eton, and Cookham (https://www.gov.uk/government/publications/jubilee-river-flood-alleviation-scheme/jubilee-riverflood-alleviation-scheme) (Accessed 8th June 2023). On a larger scale, in Canada the Red River Floodway, which is 47 km long, diverts flood flows of the Red River around Winnipeg in Manitoba (Fig. 4.5). In the USA, the New Madrid Floodway is immediately downstream of the confluence of the Mississippi and Ohio Rivers. It has a surface area of 540 km2 and provides an estimated 2 m of stage lowering in the vicinity of Cairo, Illinois.

Fig. 4.5  Google Earth image of the Red River floodway, Winnipeg, Canada. Scale bar is 7 km. Location: 49° 51′ 19.60ʺ N, 96° 59′ 7.62ʺ W

80

4.7 Canals Canals are humanly made rivers. They are artificial waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveying ships, boats, and barges. A canal can be created where no stream presently exists. Either the body of the canal is excavated or the sides of the canal are created by making dykes or levees by piling stone, concrete or other materials. The water for the canal has to be provided from an external source, such as streams or reservoirs. Where the new waterway must change elevation, engineering works like locks, lifts, or elevators are constructed to raise and lower vessels. The oldest known canals were built for irrigation in Mesopotamia circa 6000 years ago. In India, the Harappan civilisation (circa 5000 years ago) had sophisticated irrigation and storage systems developed, including reservoirs built at Girnar. In Egypt, canals date back at least to the time of Pepi I Merye (2332–2283 BC), who ordered a canal to be built to bypass the cataract on the Nile near Aswan. There were also extensive networks of canals in Arizona, built by Hohokam peoples. They used the waters of the Salt and Gila Rivers to build an assortment of simple canals with weirs for agriculture from 800 to 1400 AD. On Google Earth these show up well, as for example, to the north of the Gila River at 33° 11′ 44.21ʺ N, 111° 55′ 5.89ʺ W, but many have been built over with the growth of the city of Phoenix.

4 Rivers

By far the longest canal was the Grand Canal of China, still the longest canal in the world today and the oldest extant one. It is 1794 km long (see Fig. 4.6). Starting in  Beijing, it passes through  Tianjin  and the provinces of Hebei, Shandong, Jiangsu, and Zhejiang to the city of Hangzhou, linking the Yellow River and Yangtze River. The oldest parts of the canal date back to the fifth century BC. However, only the section from Hangzhou to Liangshan County is currently navigable. Roman engineers in Britain built the Fossdyke connecting Lincoln to the River Trent around AD50, for both drainage and navigation purposes. They also constructed the nearby Caer (or Car) Dyke, extending for almost 60 km to the south of Lincolnshire. It is believed to have provided a supply route for transporting heavy goods and supplies between Cambridge and York. In relatively modern times the Exeter Canal in Devon was built in 1566: this bypassed part of the river making navigation easier. Other early British canals include a section of the River Welland in Lincolnshire, built in 1670. However, one of the greatest eras of canal construction was the Industrial Revolution, particularly before the coming of the railways. The canals enabled the transport of the coal, iron, cotton, etc. upon which the revolution was based. The Golden Age of British canals came between 1770 and 1830. This period saw a huge rise in canal building across the country, and the network in the UK was roughly 6400 km in length.

Fig. 4.6  Google Earth image of the Grand Canal, China. Scale bar is 1 km. Location: 30° 24′ 13.98ʺ N, 120° 7′ 30.25ʺ E

4.7 Canals

Some canals cross isthmuses and so allow transit from one ocean to another, as with the case of the Suez and Panama Canals. As vessels have grown in size such canals have also had to grow, sometimes by constructing a new

81

channel parallel to the original one (see the Suez Canal in Fig. 4.7). The original 82-km-long Panama Canal was a very great excavation and involved some 185 million cubic metres of material.

Fig. 4.7  Google Earth images of the Suez Canal, Egypt, in 2012 (top) and 2022 (bottom). Scale bar is 2 km. Location: 30° 30′ 24.33ʺ N, 32° 20′ 49.71ʺ E

82

4 Rivers

4.8 Changes in River Channels as a Result of Land Use Changes 4.8.1 Introduction Having discussed some deliberate modifications of river systems, it is now time to consider how river channels have been modified by land use changes (see Fig. 4.8). Downs and Gregory (2004), Church et  al. (2009), and Downs et al. (2013) have reviewed the complexity and diversity of causes of stream channel change. Major changes in channel configuration result either because of human-induced changes in stream discharge or sediment load, and both these parameters affect channel capacity. There are numerous ‘drivers for change’ operating at multiple spatial and temporal scales, so that understanding the of channel response in the historical period requires knowledge of a suite of mechanisms for change rather than a focus on a single causal influence, be this natural or human. In Britain, Macklin et al. (2013) analysed the complex history of channel incision and noted that while climatic fluctuations explain some of the observed phases of this phenomenon during the Holocene, that in the last 1000 or so years in addition to climate change, other factors that may have contributed to increasing extreme discharge events include: large-scale channelisation to improve navigation or the siting of mills (see Sect. 4.4), the rapid expansion of arable cropland during the medieval period, and locally to urban (see Sect. 4.13.7) and industrial developments. The conversion of land from woodland to farmland at the same time as there was a wetter climate (e.g. at

Fig. 4.8  Non-deliberate causes of river channel changes (after Goudie and Viles 2016, Fig. 7.9)

ůĞĂƌͲǁĂƚĞƌ ĞƌŽƐŝŽŶ 'ƌĂǀĞůŵŝŶŝŶŐ ĨƌŽŵďĞĚ ĂŵƌĞŵŽǀĂů ZĞͲĂīŽƌĞƐƚĂƟŽŶ

900–800 years ago) would in combination have resulted in larger and more frequent floods that were capable of entraining coarser bed and bank material, thereby promoting channel entrenchment.

4.8.2 Diversity of Causes: Some Examples In Italy, Surian and Rinaldi (2003) found that particularly since the 1950s to 1960s, most Italian rivers experienced two types of channel adjustment: incision (commonly of the order of 3–4 m, but in some cases greater than 10 m); and narrowing of the active channel, in some cases by up to 50% (or even more). In some rivers, these channel adjustments, which frequently occurred together, led to a change from braided to meandering. The causes of these adjustments included land use changes such as deforestation and afforestation, channelisation, construction of dams, and sediment mining, all of which have been particularly severe since the 1950s (Scorpio et al. 2015). In Spain, the work of Uribelarrea et al. (2003) shows there have been two distinct periods: before and after human intervention in the river system, which took place around 1950. During the earlier period (1550–1950), a correlation exists between climate, frequency, and magnitude of flooding and changes in fluvial geomorphology. In the second period (1950—present), flow regulation via dams and gravel mining has modified the system completely and impeded the natural development of these rivers. The importance of gravel mining was particularly severe in the period 1950–1980, and it is a major contributor to incision in Spanish rivers (Segura-Beltrán and Sanchis-Ibor

ZĞĚƵĐƟŽŶŝŶ ŇƵƐŚŝŶŐďLJƉĞĂŬ ŇŽǁƐďĞůŽǁ ĚĂŵƐ ĚĚŝƟŽŶŽĨ ƐĞĚŝŵĞŶƚďLJ ŵŝŶŝŶŐ͕ƐŽŝů ĞƌŽƐŝŽŶ͕ĞƚĐ͘

/ŶĐƌĞĂƐĞŝŶ ĚŝƐĐŚĂƌŐĞ ƉƌŽĚƵĐĞĚďLJ ƵƌďĂŶŝƐĂƟŽŶ͕ ĐŚĂŶŐĞƐŝŶůĂŶĚ ĐŽǀĞƌ͕ŽƌŝŶƚĞƌͲ ďĂƐŝŶǁĂƚĞƌ ƚƌĂŶƐĨĞƌƐ

&ůŽǁĚĞĐƌĞĂƐĞ ĨŽůůŽǁŝŶŐ ǁĂƚĞƌ ĂďƐƚƌĂĐƟŽŶŽƌ ŇŽŽĚĐŽŶƚƌŽů ŽŶĮŶĞŵĞŶƚ ďLJƚƌĂŶƐƉŽƌƚ ůŝŶŬƐ dƌĂƉƉŝŶŐΘ ƐƚĂďŝůŝƐĂƟŽŶŽĨ ƐĞĚŝŵĞŶƚďLJ ŝŶƚƌŽĚƵĐĞĚ ƉůĂŶƚƐ

/ŶĐŝƐŝŽŶ

ŐŐƌĂĚĂƟŽŶ

ŶůĂƌŐĞŵĞŶƚ

ŝŵŝŶƵƟŽŶ

ŚĂŶŐĞŝŶ ŶĂƚƵƌĞĂŶĚ ĐŽŵƉŽƐŝƟŽŶŽĨ ƐĞĚŝŵĞŶƚůŽĂĚ ŚĂŶŐĞŝŶŇŽǁ ƌĞŐŝŵĞ EĂƚƵƌĞŽĨďĂŶŬ ǀĞŐĞƚĂƟŽŶ;Ğ͘Ő͘ ƐŽĚͲĐŽǀĞƌĞĚ ǀĞƌƐƵƐƚƌĞĞͲ ůŝŶĞĚ

WůĂŶͲĨŽƌŵ

4.8  Changes in River Channels as a Result of Land Use Changes

2013). In the case of the Bernesga River, a combination of gravel mining and channel training has caused reach-averaged incision which exceeds 8.5 m, simultaneously with a dramatic change in channel pattern: from ∼450 m-wide braided morphology around the middle of the twentieth century to a narrow single-thread (∼40 m wide) channel in 2017 (Ferrer-Boix et al. 2023). In the Ebro, the natural meandering tendency of the river has recently been transformed by large amounts of river regulation and of defence works (Ollero 2010). In the Upper Esla river of north west Spain, between 1956 and 2011, channel changes ‘included (1) channel narrowing; (2) changes in planform from active multiple channels to more stabilized wandering or singlechannel planforms; and (3) vegetation expansion within the historic active channel area of 1956 by natural vegetation encroachment and poplar plantations’ (Martínez-Fernández et al. 2017, p. 221). In the European Alps, an historical study by Hohensinner et al. (2021) showed that in the early nineteenth century, one-third of large Alpine rivers were multichannel rivers. Single-bed channels oscillating between close valley sides were also frequent in the Alps. Sinuous and meandering channels were much rarer. Multichannel reaches were widespread within the whole Alpine area, alternating with confined and oscillating reaches. Since then, channel straightening has caused the loss of about 510 km of river course length, equivalent to 4.3% of the

83

historical extent. More importantly, multichannel stretches are currently a mere 15% of their historical length, and 45% of the larger Alpine rivers are now intensively channelised or have been transformed into reservoirs. Among the causes of these changes are various types of river training. In the USA, the Platte River of Nebraska has metamorphosed in the last two centuries (Joeckel and Henebry 2008; Horn et al. 2012). The river has evolved from an open, braided condition to a stream with multiple, stable anabranches and heavily vegetated banks and islands (Fig. 4.9). The mean channel area of the central Platte decreased on average by 46% between 1938 and 2006, and the mean widths of the individual channels in 1858 were over 5 times greater than in 2006. Channel constriction, from the construction of dams and diversion canals for irrigation, and encroachment of riparian vegetation, including invasive exotics (Hoffman et al. 2008), into formerly open channels, seem to have been primarily responsible for these changes. Groundwater inputs have been reduced due to the spread of centre pivot irrigation schemes. An under-appreciated cause of channel changes in the USA has been deliberate wood removal from channels (Wohl 2014, p. 637): Removal of natural wood rafts began in the 17th century in the eastern United States and proceeded westward with the movement of European settlers, accelerating during the 19th-century era of steamboats and floating of cut timber. Removal of

Fig. 4.9  Google Earth image of the Platte River in Nebraska showing the multithread nature of the channel at the present time. Note the centre pivot fields along its banks. Scale bar is 1 km. Location: 41° 8′ 38.20ʺ N, 101° 8′ 56.35ʺ W

84

4 Rivers the natural wood rafts likely forced many rivers from a multi thread planform with high channel-floodplain connectivity into an alternative stable state of single-thread channels with substantially reduced overbank flow, sedimentation, and avulsions. There is now widespread recognition among the geomorphic community of how upland clearance increased sediment yields and floodplain aggradation. I propose that widespread removal of instream wood for steamboat routes, timber rafts, and flood control was equally significant in decreasing floodplain sedimentation and river complexity, and in causing a fundamental, extensive, and intensive change in forested river corridors throughout the United States.

In Australia, within a few decades of European settlement, dramatic channel incision occurred (Rutherford 2000; Hoyle et al. 2008), most of which was triggered by disturbances to the material making up valley floors. Drains, cattle tracks, roads, and other forms of flow concentration made the valley floors more susceptible during storms to higher runoff from cleared and trampled catchments. Other causes identified by Rutherford included channel enlargement by sand and gravel extraction, changes in flow as a result of dam construction, channel invasion by exotic vegetation, removal of riparian vegetation, and bank erosion by boats. The last of these processes was investigated by Bradbury et al. (1995). In recent years there has been some reversal of trend along rivers in eastern Australia. There has been a tendency towards reduced flow which for many rivers coincided with land use and river management changes resulting in increases in woody riparian vegetation. There has been accompanied improvement of on-farm stock-management practices (e.g. riparian fencing, off-river stock watering points), changes to sand and gravel extraction policies since the early 1990s and a change from historical river management practices that were geared towards mechanical and chemical destruction of riparian vegetation (Cohen et al. 2022a, b). As this Australian example shows, riparian vegetation can be a major control of rates of channel bank erosion, though the amount of available data is modest (Hughes 2016). Certainly, the presence of riparian forest on riverbanks significantly reduces the likelihood of erosion by mass failure due to reinforcement of riverbank soils by tree roots (Zaimes et al. 2019; Hubble et al. 2010).

4.8.3 Role of Soil Conservation Measures An interesting case study is the examination of the farreaching changes in channel form that have been produced by land use changes and the introduction of soil conservation measures (see Sect. 9.7). This was shown for the river basins of Georgia in the USA which were modified between 1700 (the time of initial European settlement) and the present (Trimble 1974). Clearing of the land for agriculture caused severe slope erosion. This resulted in the transfer

of sediment into floodplains and river channels. The phase of intense erosive land use persisted during the nineteenth century and the first decades of the twentieth century, but thereafter conservation measures, reservoir construction, and a reduction in the intensity of land use by farmers, led to further changes in channels. Streams ceased to carry such heavy sediment loads with the consequence that incision into the flood plains took place, lowering their beds by up to 3–4 m. Furthermore, stream flow and flood discharges declined following afforestation. In south-west Wisconsin Knox (1977) documented a broadly comparable picture of channel change. There, as in the Upper Mississippi Valley (Knox 1987), it is possible to identify stages of channel modification associated with various stages of land use, culminating in decreased overbank sedimentation as a result of better land management in the middle and late twentieth century.

4.8.4 Role of Invasive Plants and of Animals Riparian vegetation is an important control of river bank stability and thus of channel form (Zaimes and Schultz 2015) and, in turn, channel forms and flows affect riparian vegetation (Hupp and Osterkamp 1996). There is a general question about the ways in which different vegetation types affect channel form (Trimble 2004). Are tree-lined banks more stable than those flowing through grassland? On the one hand tree roots stabilise banks and their removal might be expected to cause channels to become wider and shallower. On the other hand, forests produce log-jams which can cause aggradation or concentrate flow onto channel banks, thereby leading to their erosion. The diversity and abundance of alien plants have increased in riparian zones throughout the world. River ecosystems are highly prone to their invasion, largely because of their dynamic hydrology and because rivers can prove to be the efficient at dispersal of propagules (Richardson et al. 2007). The western USA is an area that has proved to be of great interest because of the role of invasive Tamarix and other Eurasian aliens (Friedman et al. 2005). These were introduced to the American Southwest in the early nineteenth century and contributed to regional trends of decreasing river channel width and migration rate in the twentieth century. Invasive non-native plant species found on floodplains of the area include tamarisk (Tamarix spp.), Russian olive (Elaeagnus angustifolia), and giant cane (Arundo donax). The spreading of these woody plants along dryland channels caused channel narrowing to occur (Birken and Cooper 2006). Equally, removal of these plants has led to subsequent channel widening (Jaeger and Wohl 2011). Graf (1978) showed that the channels of the Colorado River underwent a width reduction after 1930 when invasive

4.8  Changes in River Channels as a Result of Land Use Changes

tamarisk (salt cedar) became common. Graf (1981) demonstrated that in the ephemeral Gila in Arizona channel sinuosity was increased as phreatophyte density became greater in the 1950s. However, attempts at eradication of invasive plants, particularly since the 1990s, has caused a large and consistent increase in floodplain erosion across a broad range of rivers (Wieting et al. 2022). In Hungary False Indigo (Amorpha fruticosa), which is native to the south-eastern USA, was introduced at the end of the nineteenth century to stabilise eroding riverbanks. Due to its rapid growth, this rigid plant can form 3–4 m high impenetrable thickets, decreasing river flow velocity and slowing the passage of floods. It also increases sedimentation and thereby channel form (Kiss et al. 2019). It is possible that the spread and influence of invasive alien bioengineers will be modified in a world of climate change. The reasons for this have been summarised by O’Briain et al (2023): (i) an increase in the spatial and temporal spread of propagules through waterborne dispersal during more frequent or severe flood events, (ii) increasing patch openings created by floods or droughts to provide opportunities and favourable conditions for propagule establishment and subsequent expansion, (iii) inducing a decline in native species adapted to the historical hydroclimatic regime, and/or providing conditions that favour invasive alien plant species with broader

85

environmental ranges or preadapted to an increase in abundance under the altered conditions. Changes in the populations of ecological engineers can influence of channel forms. A prime example of this is the role of beavers (Castor fiber, Castor canadensis) (Brazier et al. 2021). They have a multitude of effects on river channels and neighbouring wetlands (Fig. 4.10) and their extirpation by humans over large parts of Europe and North America in historical times had major consequences (Gurnell 1988; Butler and Malanson 2005). Butler (2006, p. 451) remarked that ‘although modern beaver ponds entrap hundreds of millions to a few billion cubic meters of sediment, these values pale in significance compared to the values associated with beavers on the pre-contact landscape when beaver ponds entrapped hundreds of billions of cubic meters of sediment. Widespread removal of North American beavers via trapping for fur led to increased stream incision, attendant changes from relatively clear-flowing to sediment-laden streams, and pronounced changes in the riparian environments of North American stream systems that are still being experienced in the twenty first Century’. But, as part of river restoration strategies they are now being re-introduced, while in some parts of the world they have exploded in numbers following being introduced by humans and have become severely invasive. Larsen et al. (2021, p. 1)

Fig. 4.10  Google Earth image of a large beaver dam and associated ponds in Alberta, Canada. Scale bar is 100 m. Location: 58° 16′ 16.73ʺ N, 112° 15′ 7.92ʺ W. The dam is c 800 m long

86

4 Rivers

have reviewed the myriad geomorphological and hydrological roles of beavers: …. a complex of beaver dams can increase surface and subsurface water storage, modify the reach scale partitioning of water budgets, allow site specific flood attenuation, alter low flow hydrology, increase evaporation, increase water and nutrient residence times, increase geomorphic heterogeneity, delay sediment transport, increase carbon, nutrient and sediment storage, expand the extent of anaerobic conditions and interfaces, increase the downstream export of dissolved organic carbon and ammonium, decrease the downstream export of nitrate, increase lotic to lentic habitat transitions and aquatic primary production, induce ‘reverse’ succession in riparian vegetation assemblages, and increase habitat complexity and biodiversity on reach scales.

Invasive beavers have had a dramatic impact in southern South America, where 20 North American beavers (C. canadensis) were introduced to Argentina from Canada in 1946. They multiplied explosively. Huertas Herrera et al. (2020) found a total of 206,203 beaver dams (100,951 in Argentina and 105,252 in Chile) in their study area of 73,000 km2. Their dam building activities and excavation of sediment had a profound influence, particularly on smaller streams (Westbrook et al. 2017).

4.8.5 The Role of Mining Humans have transformed river sediment loads globally (Cendrero et al. 2022) and this inevitably has had a major impact on channel form. For instance, humanly generated fires (see Sect. 2.4) have destabilised slopes causing pulses of sediment to enter stream channels. The addition of sediments to stream channels by mining is a cause of channel aggradation. Mine wastes can clog channel systems (Macklin and Lewin 1989) and cause them to aggrade. For example, in New Caledonia, some of the rivers are known to be highly impacted by the coarse sediment waves induced by the mining of nickel deposits that started in the early 1870s, and which was particularly intensive between the 1940s and 1970s. The propagation of the sediment pulses from the mining sites can be traced by the presence of wide and aggraded active channels along the stream network of nickel-rich peridotite massifs (Bertrand and Liébault 2019). Similarly, in south-east Australia, sediments from nineteenth century gold mining transformed channels (Davies et al. 2020), as did tin mining in Tasmania (Knighton 1989). A classic study of stream sedimentation was Gilbert’s (1917) treatise on hydraulic mining debris in the Sierra Nevada in the USA. Gilbert described immense sediment waves associated with the advent of hydraulic mining in the mountains that were passing down streams in the eastern Sacramento Valley of California. The advent of hydraulic mining in 1853 and production of 1.1 × 109 m3 of

sediment by 1884, when mining was suddenly halted by a federal court injunction, led to an unprecedented episode of rapid floodplain sedimentation downstream of the mines (James et al. 2020). James (2019) considered the extent and dating of floodplain sedimentation in the USA. Hydraulic mining for lead also led to large pulses of sediment generation in the Pennines of northern England in the eighteenth and nineteenth centuries (Kincey et al. 2022). Conversely, the mining of aggregates and minerals (placer deposits) from river beds themselves leads to bank collapse, channel deepening (Kondolf 1994; Bravard and Petts 1996) and incision (Martín-Vide et al. 2010; Arróspide et al. 2018). Sand mining is an immensely important activity and global demand has tripled in the past two decades, reaching 50 billion tonnes in 2019. Figure 4.11 shows the transformation this has caused to the morphology of the Umngi River on the borders of India and Bangladesh, with the conversion of what was a multithread sinuous river into a form with lakes and straighter channel stretches. Other excellent satellite images of this phenomenon are shown in https://www.reuters.com/graphics/GLOBALENVIRONMENT/SAND/ygdpzekyavw/ (Accessed 8th July 2023). Placer deposits are accumulations of valuable minerals both dense and resistant to weathering processes, formed by gravity separation during sedimentary processes. They include gold, platinum group minerals (PGM), tin, diamonds, rare metals, zircon-titanium mineral deposits and, in the Russian arctic zone, a specific type of related to placer deposits—fossil ivory (Bochneva et al. 2021). Figure 4.12 shows the sedimentation in a stream channel that has taken place with the development of the Ok Tedi Mine, Papua New Guinea. Mining started in 1984. Hettler et al. (1997) reported that the 1000 km long Ok Tedi/Fly River system receives about 66 Mt/year of mining waste from the Ok Tedi copper–gold porphyry mine. They also stated that the input of sediment from the mine has increased the suspended sediment load of the Middle Fly River about 5–10 times over the natural background.

4.8.6 Water Mills Water mills are powered by river water, largely diverted from rivers by leats and associated weirs. They have been used in many industrial activities, especially the milling of cereal grains and the weaving of cloth. Less common uses have included the boring of cannons, the grinding of the ingredients for gunpowder, copper smelting, hemp rollers, sawmills, and the powering of bellows for blast furnaces (Bishop and Muñoz-Salinas 2013; Jonell et al. 2023). The first water mills were developed in Greece in the third century BC. Water mills are widespread and of considerable antiquity in

4.8  Changes in River Channels as a Result of Land Use Changes

87

Fig. 4.11  Google Earth images of the Umngi River on the border between India and Bangladesh in 1985 (top) and 2023 (bottom). Scale bar is 4 km. Location: 25° 10′ 54.10ʺ N 91° 23′ 10.71ʺ E

England and Scotland (Bishop and Muñoz-Salinas 2013) and in Ireland (Rynne 2009) and have had a profound effect on river characteristics (Downward and Skinner 2005). At the time of the Domesday Book (1086) there were thousands of

them in England, and their numbers increased until c 1300 (Langdon 1991). The greatest density occurred in some of the eastern counties and around the central uplands in Wiltshire, Somerset, Gloucester, Dorset, and Hampshire

88

4 Rivers

Fig. 4.12  Google Earth images of Ok Tedi Mine in 1984 (top) and in 2018 (bottom). Note the valley sedimentation in the latter. Scale bar is 7 km. Location: 5° 11′ 42.28ʺ S, 141° 9′ 41.62ʺ E

(Hodgen 1939). Watermills were also a feature of rivers in parts of southern Italy (Grano and Bishop 2017). In many areas, such as Türkiye, they are no longer required and so are falling into disrepair or being removed (Donners et al. 2002) though there are powerful movements in some countries for their protection and restoration (Franco et al. 2019).

Wohl and Merritts (2007) regarded water mill construction as a major cause of channel change in the eastern United States. Walter and Merritts (2008), using old maps and archives, showed that whereas before European settlement the streams of the region were small anabranching channels within extensive vegetated wetlands, after the

4.8  Changes in River Channels as a Result of Land Use Changes

construction of tens of thousands of seventeenth-to-nineteenth-century mill dams, 1 to 5 m of slackwater sedimentation occurred and buried the pre-settlement wetlands with fine sediment. Where such mill dams were removed, accelerated bank erosion occurred (Pizzuto and O’Neal 2009). Buchty-Lemke and Lehmkuhl (2018) found comparable changes in Germany, as did Maaß and Schüttrumpf (2019) in the Geul River of the Netherlands.

4.8.7 Effects of Urbanisation Urbanisation affects river channels either by direct and deliberate channel modifications or as incidental results of the urbanisation process. An example of the former is the construction of a completely artificial channel for the Los Angeles River in the USA, which is constrained in a concrete corset (Fig. 4.13). When construction is initiated, streams aggrade due to increased sediment delivery to channels from cleared land or active construction sites. However, once construction ends the land surface is stabilised and sediment load is decreased, so that streams scour and erode (https://serc.carleton.edu/vignettes/collection/58524.html) (Accessed 8th June 2023). Urban development causes changes in the infiltration capacity of the land surface because of the increase of impervious surfaces such as car parks, roads, and

89

rooftops. This means that the lag time between peak precipitation and peak runoff is shortened because the flow of water in the catchment is not slowed by infiltration. Besides soil sealing, urbanisation implies an increase in population and in human activities in the catchment areas, ending up with the multiplication of sewage networks and potential urban discharge into the watercourses which accentuate the modification of the hydrological regime: culverts, storm drains, and other artificial links in the stream network increase the rate at which runoff enters a channel. Whitlow and Gregory (1989) working in Harare, Zimbabwe, found that urbanised areas evolved from a drainage density, which was initially between 0.35 and 0.80 km km−2, to one which increased to 3.15 km km−2 including stormwater drains. Characteristics of erosion of the modified urban channels are described, and the downstream reaches indicate an average channel widening of 1.7 times involving average rates of bank erosion of 0.33 m per year. Navratil et al. (2013) and Hawley et al. (2013) discussed the role of urbanisation in channel enlargement and incision, for urban development causes flashier, larger, more erosive discharges that occur with increased frequency and duration (see Sect. 2.4). In an analysis of the literature, Chin (2006) stressed how variable river channel response to urbanisation could be, but found that enlargement was reported in ∼75% of their studied catchments, with cross-sectional areas generally increasing 2–3 times and sometimes as much as 15 times. Channel

Fig. 4.13  Google Earth image of the straightened Los Angeles River in its concrete corset. Scale bar is 300 m. Location: 34° 2′ 42.19ʺ N, 118° 13′ 44.54ʺ W

90

enlargement is the reason why bank and bed reinforcement are widely used along urban rivers where space is limited and infrastructure and buildings are susceptible to undermining (Gurnell et al. 2007). Other urban-induced channel changes include (i) reductions in sinuosity, which commonly result from artificial straitening (see Sect. 4.4), (ii) a tendency (not invariable) for bed material to coarsen from scouring of fines, and (iii) increased competence because of higher peak flows. Trimble (2003) provides a good historical analysis of how the San Diego Creek in Orange County, California, has responded to flow and sediment yield changes related to the spread of both agriculture and urbanisation, while de Milleville et al. (2022) review the way in which the channel of a tributary of the Marne in France has changed.

4.8.8 Effects of Transport Corridors As Roy (2022a) has pointed out, the development of transport infrastructure has many geomorphological consequences. Valleys are often transport routes and so are often followed by roads and railways. Blanton and Marcus (2009, 2014) have considered the effects of such transport corridors on channel forms and have developed a number of hypotheses to look at the effects of what they call ‘transport disconnections’. They suggest, first of all, that these can impede the natural tendencies for meandering and migration of channels across floodplains (Blanton and Marcus 2014; Roy and Sahu 2017; Roy 2022b). Truncated meanders and reduced channel sinuosity can also be caused by confinement of roads and railways. This in turn disrupts the erosion and cut-and-fill alluviation that creates habitat and biological diversity across active channels and floodplains. Within the channel, confining structures such as bridges often concentrate energy, which leads to higher shear stress and stream power that can wash out riffles and degrade lowvelocity habitats such as pools and alcoves. There may be less channel complexity because of the presence of fewer bars and islands. Ponds, oxbow lakes, and palaeochannels with water-loving vegetation can lose their water supply as they become disconnected from the channel and therefore can shrink or disappear. This disconnected floodplain can contain a proportionally reduced proportion of stream banks with gallery forest.

4.9 Holocene and Anthropocene Floodplain Sedimentation Holocene floodplain sedimentation may be related to upstream accelerated erosion. Some of these materials have been termed ‘legacy sediments’ (Wohl 2015). Legacy

4 Rivers

sediment is deposited when intensified land use results in sediment deliveries greater than sediment transport capacity. This may lead to valley-bottom aggradation, which is ultimately followed by channel incision when the sediment wave passes and sediment loads decrease (James 2013). Macklin et al. (2014) used the term ‘Anthropocene Alluvium’ (AA) to describe floodplain sediments generated by human activities in the Holocene. In British and Irish catchments, Foulds and Macklin (2006) suggested that geomorphic instability linked with Holocene land use changes was especially intense in the Bronze and Iron Ages. Macklin et al. (2014) found that the oldest British AA units dated to the Early Bronze Age (c. 4400 cal. BP). The medieval period was also a significant one for the accelerated sedimentation of fine-grained materials, notably in smaller catchments (see also, Macklin et al. 2010), and this can be related to an agricultural revolution in the Middle Ages. There have numerous other studies of the history of erosion and alluviation in the Holocene in Europe (see, for example, Dusar et al. 2011; Notebaert and Verstraeten 2010). In Belgium, Broothaerts et al. (2014) found that typically, peat formation—in a marshy environment during the Early and Middle Holocene—was replaced by clastic overbank deposition as accelerated anthropogenic erosion and sedimentation occurred. Work in Bavaria, Germany, by Heine et al. (2005), showed how agricultural intensification led not only to floodplain sedimentation but also to slope colluviation. Lang (2003), also working in Germany, suggested that accelerated soil erosion led to phases of colluviation and alluviation in the Bronze Age, the Iron Age/Roman period and at c AD 1000. Similarly, Dreibrodt et al. (2010) found that erosion was at its maximum in the late Bronze Age and pre-Roman iron age (c 1600 BC–1000 AD), medieval times (c 1000–1350 AD), and late modern times (from c 1500 until the present). The combination of slope clearance for agriculture with times of intense storms would be an especially powerful stimulus to soil erosion, and catastrophic soil erosion in Central Europe was identified for the first half of the fourteenth century and in the mid-eighteenth to the early nineteenth century by Dotterweich (2008). Zolitschka et al. (2003), however, while recognising the possible impact of climatic fluctuations such as the Little Ice Age, argued that the general lack of synchroneity in the sedimentation record in Germany over the last 5000 years points to the importance of human activities. At a lake in Denmark, Rasmussen and Bradshaw (2005) found higher accumulation rates of minerogenic accumulation during the Late Neolithic, and indicated that this implied increased pressure on the soils resulting in increased erosion rates. The accumulation rate of minerogenic material also suggested increasing erosion throughout

4.9  Holocene and Anthropocene Floodplain Sedimentation

the Early Bronze Age and the Late Bronze Age, with a distinct peak at the end of the latter period. A survey of the Lake Jasień area (northern Poland) by Majewski (2014) demonstrated that in the early Iron Age and the pre-Roman period, deforestation may have led to activation of hillslope processes. In the French Alps, studies of lake sedimentation showed that during the Roman Period the frequency of erosive events was the highest of the last 10,000 years, and that the most intense grazing pressure on landscape occurred during the Roman occupation (GiguetCovex et al. 2014). In another study in the Alps, Arnaud et al. (2012) identified a peak of erosion in the Bronze Age associated with the onset of millet cultivation. Bertran (2004) calculated erosion rates in two small catchments of the Quercy region (south-western France) from colluvial deposits trapped in karstic depressions. These showed a progressive increase during the Holocene. Rates lower than 0.2 t ha−1 yr−1 were found for the period that covers the beginning of the Holocene to the early Iron Age. After the early Iron Age, erosion increased significantly and the mean rate reached 0.8 t ha−1 yr−1 before medieval times. The associated coarse-grained, crudely stratified colluvium is thought to reflect ploughing of the upslope fields. Erosion rates increased to c. 1.3 t ha−1 yr−1 (a more than six-fold increase compared with the early Holocene) during medieval and modem times. One interesting phenomenon in many British and European river valleys is the presence of deposits of freshwater calcareous deposits called tufas (Dabkowski 2020; Pieruccini et al. 2021). During the 1970s and 1980s an increasing body of isotopic dates became available for them. Some of these suggested that from the British Isles to the Mediterranean basin and from Spain to Slovakia, rates of tufa formation were high in the early and mid-Holocene, but declined markedly thereafter (Weisrock 1986, 165–167). Some recent studies have supported this concept. For example, in northern France at Daours tufa deposition

91

ceased just after c. 5000 year ago (Limondin-Lozouet et al. 2013). Similarly, Luzón et al. (2011) found that the reduction in tufa deposition in the Añamaza system of Central Spain also occurred at that time, as did Wehrli et al. (2010), working in Italy and Gradziński et al. (2013) working in Slovakia. If the late Holocene reduction in tufa deposition is indeed a reality (which is contested by, for example, Baker and Simms 1998), then it is necessary to consider a whole range of possible mechanisms (Table 4.3), both natural and anthropogenic (Nicod 1986: 71–80). As yet the case for an anthropogenic role remains unproven (Goudie et al. 1993) and it is possible that climate changes, such as the ending of the mid-Holocene ‘climatic optimum’, were a more important control of the tufa decline (Wehrli et al. 2010). Moreover, the ‘human impact’ theory cannot explain the cases of tufa deposition decline which repeatedly occurred before the Holocene. In some parts of Europe, tufa deposition is still occurring and the climatic factor may have been dominant in controlling tufa nature and deposition (Dabkowski et al. 2015). Nonetheless, in the Trabaque region of central Spain (Domínguez-Villar et al., 2012) there was a drastic diminution in the amount of tufa precipitation after ~4 ka BP, probably caused by anthropogenic deforestation. Widespread forest clearing, started locally in the Early Holocene and widely developed after 5 ka BP, would have drastically lowered the biogenic CO2 in soils, the CaCO3 dissolution in the limestone aquifers, and the deposition rates of tufa from spring groundwaters (Fubelli and Dramis 2023). Also working in Spain, González-Amuchastegui and Serrano (2015) found that in the Holocene, tufa deposition and erosion had responded to climatic fluctuations until c 6.5 ka BP, but subsequently human activity had determined landscape evolution and especially from 4.5 ka BP. In their study of the sediments of Kuk Swamp in Papua New Guinea Hughes et al. (1991) showed low rates of erosion until 9000 BP, when, with the onset of the first phase

Table 4.3  Possible mechanisms to account for the alleged Holocene tufa decline Climatic/natural

Anthropogenic

Discharge reduction following rainfall decline leading to less turbulence

Discharge reduction due to overpumping, diversions, etc.

Degassing leads to less deposition

Increased flood scour and runoff variability of channels due to deforestation, urbanisation, ditching, etc.

Increased rainfall causing more flood scour

Channel shifting due to deforestation of floodplains leads to tufa erosion

Decreasing temperature leads to less evaporation and more CO2 solubility

Reduced CO2 flux in system after deforestation

Progressive Holocene peat and podzol development through time leads to more acidic surface waters

Introduction of domestic stock causes breakdown of fragile tufa structures Deforestation means there are less fallen trees to act as foci for tufa barrages Increased stream turbidity following deforestation reduces algal productivity

92

of forest clearance, erosion rates increased from 0.15 cm per thousand years to about 1.2 cm per thousand years. Rates remained relatively stable until with European contact, the extension of anthropogenic grasslands, subsistence gardens and coffee plantations produced a rate that was very markedly higher: 34 cm per thousand years. In New Zealand anthropogenic land use changes have been restricted to the last ~800 years. There have been two phases of settlement. The first was by Polynesian immigrants, and the second by European colonists within the last 200 years. The Polynesian settlers caused widespread deforestation (of about 50% of the forest area), especially in the east of the South Island. After the arrival of European settlers in the early nineteenth century extensive areas (a further 30% of the country) were cleared for farming and timber, and large numbers of grazing animals were introduced to the transformed landscapes (Basher 2013). A good long-term study of the response rates of erosion to land use changes associated with these demographic changes is provided by a study undertaken on North Island by Page and Trustrum (1997). Their catchment underwent a change from indigenous forest to fern/scrub following Polynesian settlement (c. 560 BP) and then a change to pasture following European settlement (AD 1878). Sedimentation rates under European pastoral land use were between five and six times the rates that occurred under fern/scrub and between eight and seventeen times the rate under indigenous forest. In a broadly comparable study in another part of New Zealand, Sheffield et al. (1995) looked at rates of infilling of an estuary. In pre-Polynesian times rates of sedimentation were 0.1 mm per year, but during Polynesian times the rate climbed to 0.3 mm per year, while since European land clearance in the 1880s the rate has shot up to 11 mm per year (see also Nichol et al. 2000). Richardson et al. (2014) working in Kaeo, northern New Zealand, found that Holocene floodplain aggradation occurred at a rate of 0.3 to 0.7 mm per year. This was accelerated following Polynesian settlement, with aggradation rates in the vicinity of 3.3–10.1 mm per year. A sedimentation rate of at least 13.5 mm per year has characterised the last century or so of European farming. However, in some areas, afforestation since the early 1960s has reduced rates of erosion and gully formation that had been caused by this European farming, as in the East Coast Region of North Ireland (Marden et al. 2012). In Mexico and elsewhere in Central America, there have been various studies of long-term erosion and sedimentation rates. Beach et al. (2006) have suggested that rates were high in the Maya Lowlands in the Pre-Classic Period (c 1000 BC to AD 50) and in Late Classic times (c AD 550– 900). Similarly, O’Hara et al. (1993), based on the study of cores from Lake Patzcuaro in Mexico, identified high rates

4 Rivers

in the Pre-Classic/Early Classic period (2500–1300 BP) and in later Post-classic times (850–350 BP). However, Fisher et al. (2003), who also worked in Lake Patzcuaro, had a different interpretation, arguing that some high rates of erosion were associated not with intense land use, but with some phases of land abandonment, as in post-Hispanic times. Regional degradation was initiated from the disruption of a human-modified environment dependent on human labour that was lost due to the dreadful consequences of Europeanintroduced diseases. In North America Kemp et al. (2020, p. 1) undertook a continent-wide analysis of data on alluvium accumulation in river channels. They reported that ‘rates of alluvium accumulation were broadly stable for ~40,000 years, but increased tenfold during the rapid expansion of agriculture and river system modification associated with European colonization. Interpreted in terms of mass transfer, humans have moved as much sediment in North America in the past century as natural processes can transfer in 700–3000 years’.

4.10 Recent Changes in Sediment Loads Although there have been these many examples of changing rates of sedimentation as a result of human activities during the Holocene, it is clear that changes that have taken place in recent decades have been enormous (Syvitski et al. 2022, p. 1): Between 1950 and 2010, humans have transformed the mobilization, transport and sequestration of sediment, to the point where human action now dominates these fluxes at the global scale. Human activities have increased fluvial sediment delivery by 215% while simultaneously decreasing the amount of fluvial sediment that reaches the ocean by 49%, and societal consumption of sediment over the same period has increased by more than 2,500%.

They also calculated that sediment production (supply) from anthropogenic soil erosion, construction activities, mineral and aggregate mining, and sand and gravel mining from coasts and rivers, increased by about 467% between 1950 and 2010. If it were not for sequestration of sediment behind dams, they estimated that global rivers would have increased their particulate loads by 212% between 1950 and 2010. Cohen et al (2022a, b), in a global survey, showed that the proportion of sediment loads that are composed of bedload is decreasing from headwater to the coast, largely because of dam and reservoir construction. Interestingly, however, they reported that sand and gravel mining from coasts and rivers have reached ∼40 Gt per year, more than the total fluvial sediment load. River bed mining is now greatly reducing fluvial bed-material transport.

4.12  River Deltas

The following discussion of some major fluvial systems illustrates the changes in sediment loads that have occurred. Das (2021) analysed changes in sediment loads in the great rivers of peninsular India and found that after 2000, sediment load in almost all rivers declined more than 40%, largely because of the construction of numerous high capacity reservoirs and dams. In some cases sediment load reductions in peninsular India were even higher than this mean value, and Gupta et al. (2012), by comparing current and historical sediment loads, found that sediment loads of the Narmada had been reduced by 95%. Likewise, Li et al. (2020) found that in the case of the Mississippi in the USA, since the earliest estimates (initially 400–500 Mt per year), land–ocean sediment reduction in the Mississippi River system had shown two temporal phases, decreasing from 350 Mt per year during 1952–1962 to 200 Mt per year during 1963–2009. They postulated that the decline in land–ocean sediment flux was the result of an increase in precipitation and water yield capacity being outweighed by a decrease in sediment concentration. They estimated that a total of 24 Gt of sediment was trapped by dams and reservoirs from 1985 to 2015. They deduced that reservoir construction was the dominant driver (~ 62%) influencing land–ocean sediment flux from the Mississippi River system during 1985–2015. Edmonds et al (2023) reported that between 1932 and 2016, the Mississippi River delta and coastal Louisiana lost an estimated 4833 km2 of land, shrinking by nearly 25%. Among the causes were dam construction, levee development, and canal dredging and fluid extraction for the hydrocarbon industry. The whole history of the Mississippi system in the Anthropocene is reviewed by Russell et al. (2021). Yang et al. (2018) found major changes had taken place in the Yangtze River of China, because of two factors: fluvial sediment being trapped in reservoirs and soil conservation. From 1956 to 1968 (the pre-dam period) to 2013–2015 (following dam construction and soil conservation) the sediment flux decreased by 99% at Xiangjiaba (upper reach), 97% at Yichang (transition between upper and middle reaches), 83% at Hankou (middle reach), and 77% at Datong (tidal limit). On the Mekong in Southeast Asia, there has been a great spasm of dam building since 1990, and when they are completed, cumulative sediment trapping will be 96% (Kondolf et al. 2014).Chua and Lu (2022) found that at Chiang Saen in Thailand, the nearest gauging station to a series of Chinese dams across the Mekong, the average sediment load was 79 ± 32 Mt per year during the pre-dam period of 1965–1991. However, from 2010 to 2019—during which a series of mega-dams had been built—the sediment load decreased drastically by 84% to only 12.5 ± 4.6 Mt per year.

93

4.11 Fluvial Wetland Drainage River floodplains provide important wetland environments, but many of them have been transformed as a result, for example, of drainage. In Europe and the USA 90% of riverine flood plains have been gravely and extensively modified as habitats and in ecological terms have been described as ‘functionally extinct’ (Tockner and Stanford 2002) (see also Sect. 2.3). One particularly spectacular example of marshland transformation is provided by Mesopotamia. The Mesopotamian Marshes are a large area of wetland that originally covered an area of c 20,000 km2. Draining of parts of these marshes began in the 1950s and continued through the 1970s to reclaim land for agriculture and for oil exploration. The draining of the marshes was largely due to dykes, dams, and other water diversion structures constructed in Iraq itself, but these were exacerbated by upstream dam construction on the Tigris and Euphrates rivers in Syria and Türkiye. However, in the late 1980s and 1990s, while the late Saddam Hussein was President, this work developed further in part to evict Shia Muslim insurgents from the marshes (Ahram 2020). By 2003, they were so transformed that they only covered about 10% of their original area. Because they were so dry they became a substantial source of dust storms in Iran, particularly in Ahvaz city (Javadian et al. 2019). Another consequence was that when the marshes were drained they ceased to act as an efficient sediment trap, so that the rivers transported more sediment into the Arabian/Persian Gulf. Figure 4.14 (top) shows the extent of the marshes in 1984, prior to some of the major drainage works, while Fig. 4.14 (middle) shows the extent of the marshes when they were at their most reduced state. However, as Fig. 4.14 (bottom) shows there has been significant recovery since then. Almost immediately after the Hussein dictatorship collapsed in April 2003, farmers and water authorities began remedial measures, so that by February 2004, nearly 20% of the former drained marshes had been re-flooded (Richardson and Hussain 2006). Some wet years also contributed to this change (Al-Nasrawi et al. 2021). The area of open water in 2020 was similar to that in 1984, though there is interannual variability depending on drought incidence.

4.12 River Deltas Many deltas have been formed or have expanded considerably following human interventions that liberated large amounts of sediments in their catchments, especially in Europe, with examples in the Mediterranean such as the

94

4 Rivers

Fig. 4.14  Google Earth images of the Iraqi marshes between 1984 and 2020. Scale bar is 40 km. Location: 31° 2′ 27.70ʺ N, 46° 58′ 34.94ʺ E

Ebro, Ombrone, Po, Rhône, and Tiber. Deltas in southern Europe seem to have grown in Roman times as a result of increased river sediment loads caused by catchment soil erosion (Brückner 1986; Maselli and Trincardi 2013). However, more recently, delta erosion has become a pervasive and developing problem (Renaud et al. 2013), not

least in South and Southeast Asia. Day et al. (2019) have argued that most medium and large deltas face a reduction in area due to reduced sediment input and sea level rise. There are various reasons for this. Large areas in deltas have been ‘reclaimed’ for agriculture, aquaculture, urban growth, and industry. They are highly vulnerable to sea

4.12  River Deltas

95

Fig. 4.14  (continued)

level rise because of their low relief combined with high rates of natural subsidence, often exacerbated by peat oxidation and extraction of subsurface groundwater, natural gas, and petroleum. Deltas sink under their own weight of sediment. They also suffer from a reduced amount of sediment nourishment following dam construction upstream and from a reduction in the number of distributary channels as a consequence of a need to support navigation in a limited number of larger channels (Syvitski and Saito 2007; Syvitski et al. 2009). Indeed, such interventions have already been implicated in the changes that have taken place in the morphology of the Nile Delta and its lagoons over the last half century (El Banna and Frihy 2009). Anthony (2015) has argued that the current significant reductions in fluvial sediment supply to deltas may hasten the ultimate demise of many of them in coming decades through a process of delta shoreline straightening by waves, in addition to accelerated sinking. However, Ibáñez et al. (2019) have warned about overstating the role of humans in modifying delta morphology. As they wrote (p. 24): As most deltas have developed over thousands of years, the much shorter-lived anthropogenic signals from deforestation and other landscape perturbations have had only secondary impact on the total area of deltas. Also, delta progradation is strongly influenced by sand deposition, whereas anthropogenic impacts on sediment load have more often impacted mostly the finer sediment being deposited offshore (prodelta deposits) or in the deltaic plain. These data disproves the hypothesis that

delta size and growth is strongly influenced by human forcings, particularly for larger deltas, since Holocene delta building is mainly determined by natural forces.

With regard to the Mississippi Delta, Walker et al. (1987) indicated that its erosion was the result of complex interactions among a number of physical, chemical, biological, and cultural processes: channelisation, eustatic sea level changes, subsidence resulting from sediment loading by the delta of the underlying crust, changes in the sites of deltaic sedimentation as the delta evolves, catastrophic storm surges, subsidence resulting from subsurface fluid withdrawal, and changes in the amount of sediment carried by the Mississippi in response to upstream land use changes and miscellaneous types of river engineering (Tweel and Turner 2012). In China, construction of c 50,000 dams in the basin of the Yangtze has caused sediment starvation and severe delta erosion (Yang et al. 2011; Dai and Lu 2014). In contrast to the relatively slow historical increase in sediment flux during the period 2000–1000 yr BP, the recent sediment flux has been decreased at an accelerating rate over centennial scales (Wang et al. 2011). Zhang et al. (2022) noted differences between the Mississippi Delta and the Yangtze Delta with respect to recent changes. While the Yangtze Delta has seen an increase of subaerial land of ~1500 km2 since 1950, the Mississippi Delta has lost approximately 5000 km2 of land since the early 1930s. Extensive land reclamation and coastal  shoreline  embankment  in the former have led to land gain at the expense of tidal wetland shrinkage. In

96

contrast, flood control, waterway transportation, and the petroleum industry in the former have resulted in levee construction and canal building, which together with subsidence and sea level rise, have led to significant wetland loss. In addition, the tidal forcing in the Yangtze River Delta is much stronger than that in the Mississippi Delta, which has played a role in redistributing subaqueous sediment back into the delta plain. This has offset the negative effect of fluvial sediment reduction resulting from dam construction upstream. In the later decades of the nineteenth century the Nile Delta in Egypt began to retreat. Its Rosetta mouth lost about 1.6 km of its length between 1898 and 1954. The imbalance between sedimentation and erosion appears to have started with the Delta Barrages (1861) and culminated with the construction of the Aswan High Dam in 1971. In addition, large amounts of sediment are retained in an extremely dense network of irrigation channels and drains that has been developed in the Nile Delta itself (Stanley 1996). Extensive coastal protection works (seawalls, groynes, dykes, jetties, and breakwaters) have been installed at the Rosetta and Damietta headlands, and these have had some success in moderating erosion rates (Ghoneim et al. 2015; Dewidar and Bayoumi 2021), at least on the short term. While, as Ibáñez et al. (2014) showed, some deltas have characteristics that may enable them to respond positively to sea level rise (SLR), other deltas appear to be subjected to especially high rates of SLR (Pethick and Orford 2013). In the Sundarbans of Bangladesh, for example, the combined impact of land subsidence, eustatic SLR, tidal range amplification, and a decrease in freshwater inputs, results in an average rate of increase in effective SLR of 14.1 to 17.2 mm yr−1. The principal mechanism for this is the increased tidal range that occurs in estuary channels recently constricted by embankments. Of more general significance, however, is that some deltas, such as the Mekong (Van Manh et al. 2015; Schmitt et al. 2017) now suffer from virtually no aggradation (because of upstream sediment sequestration behind dams), are suffering from accelerated compaction, and are sinking many times faster than the rate of SLR (Syvitski et al. 2011). Day et al. (2019) provide a detailed analysis of the variable sustainability of deltas from all over the world. In Türkiye, the construction of a dam across the Seyhan River (Özpolat and Demir 2019) caused the river’s delta to switch from accretion to erosion. The shoreline accreted nearly  +  131 m (with a maximum rate of  +  22.9 m per year) from 1950 to 1956. Following the construction of the Seyhan Dam in 1956, there was 2293 m of retreat at the river mouth, with a maximum rate of retreat of − 37  m per year between 1956 and 2018. Dunn and Minderhoud (2022, p. 2) confirmed this for the Mekong Delta:

4 Rivers The low-lying Mekong delta, the third-largest delta in the world and predominantly located in Vietnam, has experienced severe anthropogenic disruptions in recent decades. The delta is under pressure from a growing population, expanding cities, and intensifying agriculture and aquaculture activities. As the upstream Mekong river basin is shared between five other countries (Cambodia, Thailand, Laos, Myanmar, and China) with their own demands on the river’s resources, downstream Vietnam has little control over the fluvial fluxes reaching the delta. The delta suffers from reduced sediment flows from upstream,, sediment extraction within the delta due to channel mining,, and dyke construction that impedes natural floods by restricting connectivity between rivers and floodplains, as well as accelerated subsidence due to groundwater pumping, on top of already high rates of natural compaction and other land-use induced subsidence processes, such as drainage or infrastructural loading.

Dramatic changes have also taken place in the neighbouring Red River delta of Vietnam (Quang et al. 2023), which was associated with the operation of large dam-reservoirs upstream. The evolution of the Ba Lat delta lobe was found to be highly correlated with sediment load, with a huge sediment supply from the Red River causing the delta lobe to Table 4.4  Causes of changes in stream flow Engineering Barrages Channelisation Dams and reservoirs Embankments Bridges Groundwater depletion Interbasin water transfers Land drainage Log jam removal Ponds Land use and land cover changes Afforestation Cropping Deforestation Fires Invasive plants, spread of Reforestation Removal or introduction of riparian and floodplain vegetation Soil compaction Swamp encroachment Urbanisation Water impoundment in paddy fields Anthropogenic climate changes Decay of permafrost Glacier melting Increased evapotranspiration Precipitation amount Precipitation intensity Precipitation types (snow versus rainfall) Rain-on-snowfall events Carbon dioxide fertilisation Increased water efficiency of plants

4.13  Flooding and Runoff Changes

move seaward at a rate of more than 100 m per year between 1975 and 1990. However, since the early 1990s, the annual sediment flux has reduced by 57%, resulting in more than 50% of the delta lobe’s shoreline experiencing severe erosion. Dunn et al. (2019) have attempted to model future changes in deltaic environments. Their projections show major declines in fluvial sediment supply to many of the world’s major deltas over the remainder of the twenty-first century. They believe that mean sediment supply to the 47 major deltas they analysed, decreased on average by 38% (2500 Mt per year) between 1990–2019 and 2070–2099. Dam construction is projected to cause the largest changes in sediment supply, decreasing delivery to the deltas by 30% (2000 Mt per year).

4.13 Flooding and Runoff Changes Stream runoff quantities and propensity to flooding have been affected by a very wide range of factors. The cause of changes in stream flow and flooding are multiple (see Table 4.4).

4.13.1 Groundwater Depletion One of these is groundwater depletion. The rate of global groundwater depletion probably more than doubled during the period 1960–2000 (Aeschbach-Hertig and Gleeson 2012). Most of the major aquifers in the world’s arid and semi-arid zones are experiencing rapid rates of groundwater depletion (Famiglietti 2014). Groundwater is being pumped at far greater rates than it can be naturally replenished, so that many of the largest aquifers on most continents are being mined (see Sect. 2.3). These include the North China Plain, Australia’s Canning Basin, the Northwest Sahara Aquifer System, the Guarani Aquifer in South America, the High Plains and Central Valley aquifers of the USA, and the aquifers beneath north-western India and the Middle East. Where groundwater levels lie below nearby streams, as they are in many parts of the USA, stream water can infiltrate through the streambed, reducing stream flow and recharging the aquifer (Jasechko et al. 2021). Flows, especially in streams in sedimentary rocks where groundwater makes a major contribution to stream discharges, may be reduced as a result of aquifer drawdown. Zektser et al. (2005) established that extensive irrigational pumping has caused stream flow depletion, more severely, in the Northern High Plains, and to a lesser extent in the Southern High Plains of the USA, a finding that was confirmed for Nebraska by Wen and Chen (2006). Condon and Maxwell (2019) summarised studies that showed declining stream flow in all of the stations evaluated in Nebraska, 85% of stations in Kansas, 50% of stations in Oklahoma, and 33% of stations in Colorado. Another study of the Republican River Basin in south-western

97

Nebraska found a 75% decrease in the mean annual flow of the river near its entry to Kansas. Rugel et al. (2012) established that karstic groundwater exploitation in Georgia had also led to flow declines, while in northern California stream flow depletion was associated with residential uses and cannabis cultivation (Zipper et al. 2019). Low flow levels caused by groundwater exploitation have also affected the Ganges (Mukherjee et al. 2018). Climate change, through increased irrigation demand, may have a major impact on future groundwater depletion volumes (de Graaf et al. 2019).

4.13.2 Forest Removal Establishment of the links between stream flow diminution and deforestation is not always simple, for climatic fluctuations can also cause changes in discharge (Limberger et al. 2021). Nonetheless there is a long history of convincing studies, often using paired catchment techniques, which have demonstrated the link (e.g. Hornbeck et al. 1970). The first such experiment, in which a planned land use change was carried out to enable observation of the effects on stream flow, began at Wagon Wheel Gap (Colorado, USA), in 1910 (Bates 1921; Meisinger 1922). Here stream flows from two similar catchments of c 80 ha each were compared for eight years. One valley was then clear-felled and the records were continued. After the clear-felling the annual water yield was 17% above that predicted from the flows of the unchanged control valley. The substitution of one forest type for another may also affect stream flow. This can be demonstrated from the Coweeta catchments (North Carolina, USA), where paired catchment studies have been conducted since 1934 (Elliott and Vose 2011; Miniat et al. 2021). Here two experimental catchments were converted from a mature deciduous hardwood forest cover to a cover of white pine (Pinus strobus). Fifteen years after the conversion, annual stream flow had been reduced by about 20% (Swank and Douglass 1974), largely because during the dormant season the interception and subsequent evaporation of rainfall is greater for pine that it is for hardwoods. Studies have also been undertaken outside of the USA. For example, in central Queensland, Australia, Siriwardena et al. (2006) investigated the results of Brigalow (Acacia harpophylla) forest clearance in the 1960s and its replacement with grass and cropland. They found that runoff in the post-clearing period was greater by 58% than if clearing had not taken place. In Amazonia, the replacement of forest with soy cultivation (see Sect. 2.5) also had major consequences for stream flow (Hayhoe et al. 2011). One type of deforestation that has an impact on stream flow is ‘salvage logging’ that takes place following tree infestation by beetles and other insects (see, e.g., Pomeroy et al. 2012), though the overall effect of such organisms,

98

often introduced by humans, is probably minor (Zhang and Wei 2021). Extreme fire events (see, e.g., Smith et al. (2011) and Sect. 2.4), and die-off following anthropogenic drought may also affect stream flow (Adams et al. 2012). Fires often cause hydrophobic soils, with reduced soil infiltration and acceleration of surface runoff and soil erosion, particularly in semi-arid regions. Forest removal and its replacement with other land uses and land cover (e.g. pastures, crops or bare ground) effects stream flow in many ways. First, forests modify snow accumulation and ablation (Schelker et al. 2013). Lin and Wei (2008) studied the Willow watershed in central British Columbia, Canada, and argued that forest harvesting significantly increased peak flows in spring because of an increase of snow accumulation and an acceleration of snowmelt as a result of removal of forest vegetation. Secondly, mature forests probably have higher rainfall interception rates, an ability to reduce rates of overland flow, and the generation of soils with higher infiltration capacities and a better general structure. Together, these factors tend to produce both a reduction in overall runoff levels and less extreme flood peaks.

4.13.3 Afforestation Although deforestation has been prevalent in many parts of the world, a phenomenon called the ‘forest transition’, a shift from net deforestation to net reforestation has taken place in some locations (see Sect. 2.5) (Meyfroidt and Lambin 2009). Around the Mediterranean Sea, for instance, much farmland has been abandoned, caused by migration to cities or overseas and because farming may have become unprofitable in areas with steep slopes, small field sizes, and with difficulties for access and mechanisation (García-Ruiz et al. 2011). In the north-eastern USA the forested area has increased quite markedly since the 1930s and 1940s, though it is possible that some authors have exaggerated the extent of abandoned agricultural land and the amount of forest regrowth that has occurred (Ramankutty et al. 2010). Afforestation and reforestation tend to reverse the effects of deforestation. For example, López-Moreno et al., (2006) showed that in the Ebro basin of Spain, there has been a general negative trend in flood intensity in recent decades, together with an increase in the importance of low flows in the total annual contribution. They attributed this to the increase in vegetation cover that is a consequence of the farmland abandonment and reforestation that occurred during the twentieth century. Comparable trends have been reported from the Pyrenees (Buendia et al. 2016) and from rural central France (Foucher et al. 2019). This latter study showed a substantial decline (71–78%) of rural population which occurred simultaneously with a sharp decline (85–95%) in the area of arable

4 Rivers

land and with sediment deliveries significantly decreased (75–99%). Increasing forest cover in Uruguay has had similar consequences (Silveira and Alonso 2009). Fears have also been expressed that the replacement of tall natural forests by eucalyptus will produce a decline in stream flow, though this is the subject of debate (Bruijnzeel 1990). Farley et al. (2005), based on an analysis of global data, discovered that annual runoff was reduced on average by 44% and 31% when grasslands and shrublands were afforested, respectively. They suggested that reductions in runoff may be most severe in drier regions, and that in a region where natural runoff is less than 10% of mean annual precipitation, afforestation could lead to a complete loss of runoff. Where natural runoff is 30% of precipitation, runoff will probably be cut by half or more when trees are planted. They also established that eucalyptus afforestation of grasslands could lead to a 75% reduction in runoff, whereas pines led to a 40% decrease.

4.13.4 Riparian Vegetation and the Spread of Invasive Plants Introduced plants (see Sect. 4.8.4) can have an influence on river flow. For example, Tamarix has altered river flow in the south-west USA. With roots either in the water table or freely supplied by the capillary fringe, these shrubs transpire freely. Thus, their removal can lead to large increases in stream flow, though Hultine and Bush (2011) suggested that the hydrological impact of this non-native riparian vegetation may be less serious than has sometimes been proposed. Prosopis juliflora, which is an evergreen tree that can form dense stands, is another invasive plant that appears to lead to major water loss in comparison to native vegetation, as has been the case in Ethiopia (Shiferaw et al. 2023). In southern Africa, the spread of introduced and invasive plants may also cause greater loss of water than the native vegetation and so lead to reductions in stream flow. Le Maitre et al. (2000) working on the Vaal River, estimated that the incremental water use of alien plants is equivalent to a 190 mm reduction in annual rainfall, and is equivalent to almost three-quarters of the virgin mean annual runoff of the river. Also in South Africa, Rebelo et al. (2022) found that the clearing of mature infestations of alien trees, such as pines, from naturally tree-less ecosystems, can increase available surface water resources by around 15–30%. In Chile, Lara et al. (2021) found that removal of invasive eucalyptus forests caused a major increase in stream flow. However, this tendency is not universal. Nayak et al. (2023), working in the mountainous terrains of South India found that the spread of wattles (Acacia) increased flood flows for three possible reasons: (i) their litter may not integrate as well into the soil compared with native vegetation and thereby not aid

4.13  Flooding and Runoff Changes

99

infiltration, resulting in increased overland flow; (ii) a greater soil repellency is observed in areas under wattle cover compared with areas under native grassland and shrubs, which is associated with a greater risk of overland flow; (iii) wattles have root systems which increase lateral soil permeability, which could speed water to streams in extreme events. Spreading wattle roots enhance rapid, shallow subsurface flows in catchments that have suffered invasion.

and Lyon (2021) examined flow records of areas that had been drained by tile drains and found that heavily drained catchments (> 40% of catchment area) consistently reported flashier stream flow behaviour compared to those with low percentages of tile drainage ( 2000 m) where the snowpack will still be present during most of the year, but liquid precipitation will become more frequent.

4.13  Flooding and Runoff Changes

103

Fig. 4.17  Google Earth images of flooding of the Indus River, Pakistan. Top, the situation in August 2021. Bottom, the situation in September 2022. Scale bar is 2 km. Location: 26° 29′ 27.06ʺ N, 67° 52′ 44.26ʺ E

As snowfall is replaced by rainfall, the amount and seasonality of runoff will change. For example, models suggest that the Rhine’s discharge will become markedly more seasonal by the end of the century with mean discharge

decreases of about 30% in summer and increases by about 30% in winter (Shabalova et al. 2003). The increase in winter discharge will be caused by a combination of increased precipitation, reduced snow storage and increased early

104

melt. The decrease in the summer discharge is related mainly to a predicted decrease in precipitation combined with increases in evapotranspiration. Glacier melting in the Alps also contributes to the flow of the Rhine. Once these glaciers have wasted away, this contribution will diminish sharply. On a global basis it is highly likely that through a combination of increasing numbers of people and changing climate there will be increased human and economic losses from flooding (Dottori et al. 2018), and it has been estimated that flood risk in the Indian Subcontinent and East Asia will increase (Winsemius et al. 2016). In 2022, a huge amount of flooding occurred in Pakistan, and onethird of the country was under water (Fig. 4.17). The floods affected at least 33 million people in 72% of the country’s districts and were caused by an extreme monsoon season. The floods led to more than 1000 human casualties, the deaths of 1.2 million livestock (Nanditha et al. 2023), and a marked increase in fatalities caused by malaria. Otto et al. (2023) showed that the majority of the models and observations they made indicated that intense monsoonal rainfall had become heavier as Pakistan had warmed. Some of their models suggested that climate change could have increased the rainfall intensity up to 50%. By contrast, in some parts of the world, there is likely to be an intensification of drought, and this has been identified as a threat to flows in the Missouri River in the USA (Martin et al. 2020). Overpeck and Udall (2020) have written about ‘the aridification of North America’ and suggest that the growing co-occurrence of hot and dry summer conditions may in the future extend all of the way to the east coast of North America, deep into Canada, and south into Mexico. Over the last century or so, largely because of increased drought, snowpack disappearance, and increased evapotranspiration (mainly driven by snow loss and a consequent decrease in reflection of solar radiation), the flows of the Colorado River have declined by 16–20% (Xiao et al. 2018; Hoerling et al. 2019; Milly and Dunne 2020). In glacial regions, accelerated glacier melting will impact upon river flows. At first a lot of flow may be generated (‘peak flow’) but as the glaciers diminish in size the amount of water liberated by their melting declines, reaching zero when the glacier has disappeared (Huss and Hock 2018). There are some ranges, such as the North Caucasus and the Eastern Tienshan, where ‘peak flow’ has already occurred (Rets et al. 2020; Jia et al. 2020). Bliss et al. (2014) undertook a global survey of stream flow response to glacier melting from now to the end of the century. They suggested that the magnitude and sign of trends in annual runoff totals will differ considerably depending on the balance between enhanced melt and the reduction of the glacier reservoir by glacier retreat and shrinkage. In their analysis, most regions exhibited a fairly steady decline in

4 Rivers

runoff, demonstrating that they have passed their peak runoff. Among the projections were the following: runoff from glaciers in Western Canada and the USA was predicted to decline by 72% between 2003–2022 and 2080–2099; low latitudes were predicted to exhibit the fastest runoff decline (96%) due to the rapid and near complete volume loss of ice from mountains (see Sect. 5.4); runoff will be stable for a few decades and then will decline (by 29% in Alaska and by 25% in the southern portion of Arctic Canada); and Iceland, Svalbard, and South Asia will experience increasing runoff until the middle of the century, peaking 22%, 54%, and 27% higher than the initial period and declining thereafter, ending 30%, 10%, and 11% below their initial values, respectively. However, in the northern portion of Arctic Canada and the Russian Arctic, it was predicted the runoff will steadily increase throughout most of the twenty-first century, ending 36% and 85% higher than it was at its start. The melting of rock glaciers may contribute to increased water flow under global warming, though it is probable that they may react more slowly than ordinary glaciers (Jones et al. 2019a, b).

4.14 Conclusion In conclusion, many rivers across the world have experienced significant stream flow changes over the last decades (Salmoral et al. 2015). Drivers of these are multiple, including climate change, land use and land cover changes, water transfers and river impoundment. Many of these drivers interact simultaneously, sometimes making it difficult to discern the impact of each driver individually.

References Adams HD, Luce CH, Breshears DD, Allen CD, Weiler M, Hale VC, Huxman TE (2012) Ecohydrological consequences of droughtand infestation-triggered tree die-off: insights and hypotheses. Ecohydrology 5:145–159 Aeschbach-Hertig W, Gleeson T (2012) Regional strategies for the accelerating global problem of groundwater depletion. Nat Geosci 5:853–861 Angelakis AN, Antoniou G, Voudouris K, Kazakis N, Dalezios N, Dercas N (2020) History of floods in Greece: causes and measures for protection. Nat Hazards 101:833–852 Ahram AI (2020) Development, counterinsurgency, and the destruction of the Iraqi marshes. Int J Middle East Studies 47(3):447–466 Al-Nasrawi AK, Fuentes I, Al-Shammari D (2021) Changes in Mesopotamian wetlands: investigations using diverse remote sensing datasets. Wetlands 41:1–17 Anthony EJ (2015) Wave influence in the construction, shaping and destruction of river deltas: a review. Marine Geol 361:53–78 Arnaud F, Révillon S, Debret M, Revel M, Chapron E, Jacob J, Magny M (2012) Lake Bourget regional erosion patterns reconstruction reveals Holocene NW European Alps soil evolution and paleohydrology. Quat Sci Rev 51:81–92

References Arnell NW, Halliday SJ, Battarbee RW, Skeffington RA, Wade AJ (2015) The implications of climate change for the water environment in England. Progr Phys Geogr 39(1):93–120 Arróspide F, Mao L, Escauriaza C (2018) Morphological evolution of the Maipo River in central Chile: influence of instream gravel mining. Geomorphology 306:182–197 Ashmore P, McDonald J, Barlow V (2023) Multi-decadal changes in river morphology in an urbanizing watershed: highland Creek, Toronto, Canada. Geomorphology 433:108710 Baker A, Simms MJ (1998) Active deposition of calcareous tufa in Wessex, UK, and its implications for the ‘late-Holocene tufa decline.’ Holocene 8:359–365 Basher LR (2013) Erosion processes and their control in New Zealand. In: Dymond JR (ed) Ecosystem services in New Zealand—conditions and trends. Manaaki Whenua Press, Lincoln, New Zealand, pp 363–384 Bates CG (1921) First results in the streamflow experiment, Wagon Wheel Gap, Colorado. J Forestry 19(4):402–408 Beach T, Dunning N, Luzzadder-Beach S, Cook DE, Lohse J (2006) Impacts of the ancient Maya on soils and soil erosion in the central Maya Lowlands. CATENA 65:166–178 Belletti B et al (2020) More than one million barriers fragment Europe’s rivers. Nature 588:436–441 Beniston M, Stoffel M (2016) Rain-on-snow events, floods and climate change in the Alps: events may increase with warming up to 4 ℃ and decrease thereafter. Sci Total Environ 571:228–236 Bertran P (2004) Soil erosion in small catchments of the Quercy region (southwester France) during the Holocene. Holocene 14:597–606 Bertrand M, Liébault F (2019) Active channel width as a proxy of sediment supply from mining sites in New Caledonia. Earth Surf Proc Landf 44(1):67–76 Birken AS, Cooper DJ (2006) Processes of Tamarix invasion and floodplain development along the lower Green River, Utah. Ecological Appl 16:1103–1120 Bishop P, Muñoz-Salinas E (2013) Tectonics, geomorphology and water mill location in Scotland, and the potential impacts of mill dam failure. Appl Geogr 42:195–205 Blanton P, Marcus WA (2009) Railroads, roads and lateral disconnection in the river landscapes of the continental United States. Geomorphology 112(3–4):212–227 Blanton P, Marcus WA (2014) Roads, railroads, and floodplain fragmentation due to transportation infrastructure along rivers. Ann Ass Am Geogr 104(3):413–431 Bliss A, Hock R, Radić V (2014) Global response of glacier runoff to twenty-first century climate change. J Geophys Res: Earth Surf 119:717–730 Bochneva A, Lalomov A, LeBarge W (2021) Placer mineral deposits of Russian Arctic zone: genetic prerequisites of formation and prospect of development of mineral resources. Ore Geol Rev 138:104349 Bradbury J, Cullen P, Dixon G, Pemberton M (1995) Monitoring and management of streambank erosion and natural revegetation on the lower Gordon River, Tasmanian Wilderness World Heritage Area, Australia. Environ Manag 19:259–272 Brander KE, Owen KE, Potter KW (2004) Modelled impacts of development type on runoff volume and infiltration performance. J Am Water Res Ass 40:961–969 Brattebo BO, Booth DB (2003) Long-term stormwater quantity and quality performance of permeable pavement systems. Water Res 37:4369–4376 Bravard JP, Petts GE (1996) Human impacts on fluvial hydrosystems. In: Petts GE, Amoros C (eds) The fluvial hydrosystems. Springer, Dordrecht, pp 242–262 Brazier RE, Puttock A, Graham HA, Auster RE, Davies KH, Beaver BCM (2021) Nature’s ecosystem engineers. Wiley Interdisc Rev: Water 8(1):e1494

105 Brierley GJ et al (2023) Reanimating the strangled rivers of Aotearoa New Zealand. Wiley Interdisc Rev: Water 10(2):e1624 Brookes A (1987) River channel adjustments downstream from channelization works in England and Wales. Earth Surf Proc Landf 12:337–351 Broothaerts N, Notebaert B, Verstraeten G, Kasse C, Bohncke S, Vandenberghe J (2014) Non-uniform and diachronous Holocene floodplain evolution: a case study from the Dijle catchment, Belgium. J Quat Sci 29:351–360 Brown AG et al (2017) The geomorphology of the Anthropocene: emergence, status and implications. Earth Surf Proc Landf 42(1):71–90 Brückner H (1986) Man’s impact on the evolution of the physical environment in the Mediterranean region in historical times. GeoJournal 13:7–17 Bruijnzeel LA (1990) Hydrology of moist tropical forests and effects of conversion: a state of knowledge review. Free University for UNESCO International Hydrological Programme, Amsterdam, p 224 Buchty-Lemke M, Lehmkuhl F (2018) Impact of abandoned water mills on Central European foothills to lowland rivers: a reach scale example from the Würm River, Germany. Geogr Ann: a, Phys Geogr 100(3):221–239 Buendia C, Batalla RJ, Sabater S, Palau A,Marcé R (2016) Runoff trends driven by climate and afforestation in a Pyrenean Basin. Land Degrad Develop27(3):823–838 Butler DR (2006) Human-induced changes in animal populations and distributions, and the subsequent effects on fluvial systems. Geomorphology 79:448–459 Butler DR, Malanson GP (2005) The geomorphic influences of beaver dams and failures of beaver dams. Geomorphology 71(1–2):48–60 Campisano A et al (2017) Urban rainwater harvesting systems: research, implementation and future perspectives. Water Res 115:195–209 Carrer M, Dibona R, Prendin AL, Brunetti M (2023) Recent waning snowpack in the Alps is unprecedented in the last six centuries. Nat Clim Change 13:155–160 Cendrero A et al (2022) Denudation and geomorphic change in the Anthropocene; a global overview. Earth Sci Rev 233:104186 Chand SS et al (2023) Declining tropical cyclone frequency under global warming. Nat Clim Change 12(7):655–661 Chen J, Theller L, Gitau MW, Engel BA, Harbor JM (2017) Urbanization impacts on surface runoff of the contiguous United States. J Environ Manage 187:470–481 Chen Y, Chang Z, Xu S, Qi P, Tang X, Song Y, Liu D (2021) Altitudinal gradient characteristics of spatial and temporal variations of snowpack in the Changbai Mountain and their response to climate change. Water 13(24):3580 Chin A (2006) Urban transformation of river landscapes in a global context. Geomorphology 79:460–487 Chua SD, Lu XX (2022) Sediment load crisis in the Mekong River Basin: severe reductions over the decades. Geomorphology 419:108484 Church MJ, Burt T, Galay VJ, Kondolf GM (2009) Rivers. In: Slaymaker O, Spencer T, Embleton-Hamann C (eds) Geomorphology and global environmental change. Cambridge University Press, Cambridge, pp 98–129 Cohen S, Syvitski J, Ashley T, Lammers R, Fekete B, Li HY (2022) Spatial trends and drivers of bedload and suspended sediment fluxes in global rivers. Water Resourc Res 58(6):e2021WR031583 Cohen TJ, Suesse T, Reinfelds I, Zhang N, Fryirs K, Chisholm L (2022b) The re-greening of east coast Australian rivers: an unprecedented riparian transformation. Sci Total Environ 810:151309 Condon LE, Maxwell RM (2019) Simulating the sensitivity of evapotranspiration and streamflow to large-scale groundwater depletion. Sci Adv 5(6):eaav4574

106 Cotterill D, Stott P, Christidis N, Kendon E (2021) Increase in the frequency of extreme daily precipitation in the United Kingdom in autumn. Weather Clim Extremes 33:100340 Dabkowski J (2020) The late-Holocene tufa decline in Europe: myth or reality? Quat Sci Rev 230:106141 Dabkowski J, Brou L, Naton HG (2015) New stratigraphic and geochemical data on the Holocene environment and climate from a tufa deposit at Direndall (Mamer Valley, Luxembourg). Holocene 25:1153–1164 Dai SB, Lu XX (2014) Sediment load change in the Yangtze River (Changjiang): a review. Geomorphology 215:60–73 Das S (2021) Dynamics of streamflow and sediment load in peninsular Indian rivers (1965–2015). Sci Total Environ 799:149372 Davies P, Lawrence S, Turnbull J, Rutherfurd I, Grove J, Silvester E, Macklin M (2020) Mining modification of river systems: a case study from the Australian gold rush. Geoarchaeology 35(3):384–399 Day JW, Ramachandran R, Giosan L, Syvitski J, Kemp GP (2019) Delta winners and losers in the Anthropocene. In: Wolanski E, Day JW, Elliot M, Ramachandran R (eds) Coasts and estuaries. Elsevier, Amsterdam, pp 149–165 de Graaf IE, Gleeson T, Van Beek LPH, Sutanudjaja EH, Bierkens MF (2019) Environmental flow limits to global groundwater pumping. Nature 574:90–94 de Milleville L, Gob F, Thommeret N, Lespez L, Tales É, Zahm A, Girondin M (2022) The heterogeneity of the hydromorphological responses of a stream to the urbanisation of its basin. Earth Surf Proc Landf. https://doi.org/10.1002/esp.5514 Demaria EM, Roundy JK, Wi S, Palmer RN (2016) The effects of climate change on seasonal snowpack and the hydrology of the northeastern and upper Midwest United States. J Climate 29(18):6527–6541 Dewidar K, Bayoumi S (2021) Forecasting shoreline changes along the Egyptian Nile Delta coast using Landsat image series and geographic information system. Environ Monitoring Assessment 193(7):429 Dickson KE, Dzombak DA (2019) Drivers of interbasin transfers in the United States: insights from sampling. J Am Water Res Ass 55(4):1038–1052 Domínguez-Villar D, Vázquez-Navarro JA, Carrasco RM (2012) Mid-Holocene erosive episodes in tufa deposits from Trabaque Canyon, central Spain, as a result of abrupt arid climate transitions. Geomorphology 161:15–25 Donners K, Waelkens M, Deckers J (2002) Water mills in the area of Sagalassos: a disappearing ancient technology. Anatol Stud 52:1–17 Dotterweich M (2008) The history of soil erosion and fluvial deposits in small catchments of central Europe: deciphering the longterm interaction between humans and the environment—a review. Geomorphology 101:192–208 Dottori F et al (2018) Increased human and economic losses from river flooding with anthropogenic warming. Nat Clim Change 8(9):781–786 Downs PW, Gregory KJ (2004) River channel management. Arnold, London, p 408 Downs PW, Dusterhoff SR, Sears WA (2013) Reach-scale channel sensitivity to multiple human activities and natural events: lower Santa Clara River, California, USA. Geomorphology 189:121–134 Downward S, Skinner K (2005) Working rivers: the geomorphological legacy of English freshwater mills. Area 37:138–147 Draut AE (2012) Effects of river regulation on aeolian landscapes, Colorado River, southwestern USA. J Geophys Res: Earth Surf 117(F2). https://doi.org/10.1029/2011JF002329 Dreibrodt S, Lubos C, Terhorst B, Damm B, Bork H-R (2010) Historical soil erosion by water in Germany: scales and archives, chronology, research perspectives. Quat Int 222:80–95

4 Rivers Dunn FE, Minderhoud PSJ (2022) Sedimentation strategies provide effective but limited mitigation of relative sea-level rise in the Mekong delta. Commun Earth Environ 3(2). https://doi. org/10.1038/s43247-021-00331-3 Dunn FE, Darby SE, Nicholls RJ, Cohen S, Zarfl C, Fekete BM (2019) Projections of declining fluvial sediment delivery to major deltas worldwide in response to climate change and anthropogenic stress. Environ Res Lett 14(8):084034 Dusar B, Verstraeten G, Notebaert B, Bakker J (2011) Holocene environmental change and its impact on sediment dynamics in the Eastern Mediterranean. Earth Sci Rev 108:137–157 East AE, Harrison LR, Smith DP, Logan JB, Bond RM (2023) Six years of fluvial response to a large dam removal on the Carmel River, California, USA. Earth Surf Proc Landf 48(8):1487–1501 Edmonds DA, Toby SC, Siverd CG, Twilley R, Bentley SJ, Hagen S, Xu K (2023) Land loss due to human-altered sediment budget in the Mississippi River Delta. Nat Sustain:61–68. https://doi. org/10.1038/s41893-023-01081-0 El Banna MM, Frihy OE (2009) Human-induced changes in the geomorphology of the northeastern coast of the Nile delta, Egypt. Geomorphology 107:72–78 Elliott KJ, Vose JM (2011) The contribution of the Coweeta Hydrologic Laboratory to developing an understanding of longterm (1934–2008) changes in managed and unmanaged forests. Forest Ecol Manage 261(5):900–910 Famiglietti JS (2014) The global groundwater crisis. Nat Clim Change 4(11):945–948 Farley KA, Jobbágy EG, Jackson RB (2005) Effects of afforestation on water yield: a global synthesis with implications for policy. Global Change Biol 11:1565–1576 Ferrer-Boix C, Scorpio V, Martín-Vide JP, Núñez-González F, Mora D (2023) Massive incision and outcropping of bedrock in a former braided river attributed to mining and training. Geomorphology 436:108774 Fisher CT, Pollard HP, Israde-Alcántara I, Garduño-Monroy VH, Banerjee SK (2003) A reexamination of human-induced environmental change within the Lake Patzcuaro Basin, Michoacan, Mexico. Proc Nat Acad Sci 100:4957–4962 Foley MM et al (2017) Dam removal: listening in. Water Resour Res 53(7):5229–5246 Foucher A, Evrard O, Chabert C, Cerdan O, Lefèvre I, Vandromme R, Salvador-Blanes S (2019) Erosional response to land abandonment in rural areas of Western Europe during the Anthropocene: a case study in the Massif-Central. France. Agric Ecosyst Environ 284:106582 Foulds SA, Macklin MG (2006) Holocene land-use change and its impact on river basin dynamics in Great Britain and Ireland. Progr Phys Geogr 30:589–604 Franco W, Ferraresi C, Revelli R (2019) Functional analysis of Piedmont (Italy) ancient water mills aimed at their recovery or reconversion. Machines 7(2):32 Frans C, Istanbulluoglu E, Mishra V, Munoz-Arriola F, Lettenmaier DP (2013) Are climatic or land cover changes the dominant cause of runoff trends in the Upper Mississippi River Basin? Geophys Res Lett 40:1104–1110 Friedman JM, Auble GT, Shafroth PB, Scott ML, Merigliano MF, Freehling MD, Griffin ER (2005) Dominance of non-native riparian trees in western USA. Biol Invasions 7:747–751 Fubelli G, Dramis F (2023) Calcareous tufa: deposition and erosion during geological times. Appl Sci 13(7):4410 Fyfe JC et al (2017) Large near-term projected snowpack loss over the western United States. Nat Commun 8(1):14996 García-Ruiz JM, López-Moreno JI, Vicente-Serrano SM, LasantaMartínez T, Beguería S (2011) Mediterranean water resources in a global change scenario. Earth Sci Rev 105:121–139

References Garner G, Hannah DM, Watts G (2017) Climate change and water in the UK: recent scientific evidence for past and future change. Progr Phys Geogr 41(2):154–170 Gedney N, Cox PM, Betts RA, Boucher O, Huntingford C, Stott PA (2006) Detection of a direct carbon dioxide effect in continental river runoff records. Nature 439:835–838 Gergel DR, Nijssen B, Abatzoglou JT, Lettenmaier DP, Stumbaugh MR (2017) Effects of climate change on snowpack and fire potential in the western USA. Clim Change 141(2):287–299 Ghassemi F, White I (2007) Inter-basin water transfer: case studies from Australia, United States, Canada, China and India. Cambridge University Press, Cambridge, p 462 Ghoneim E, Mashaly J, Gamble D, Halls J, AbuBakr M (2015) Nile Delta exhibited a spatial reversal in the rates of shoreline retreat on the Rosetta promontory comparing pre-and post-beach protection. Geomorphology 228:1–14 Giguet-Covex C, Pansu J, Arnaud F, Rey PJ, Griggo C, Gielly L, Taberlet P (2014) Long livestock farming history and human landscape shaping revealed by lake sediment DNA. Nat Commun 5.https://doi.org/10.1038/ncomms4211 Gilbert GK (1917) Hydraulic-mining débris in the Sierra Nevada. US Geol Surv Prof Paper 105:154 Gonsamo A et al (2021) Greening drylands despite warming consistent with carbon dioxide fertilization effect. Glob Change Biol 27(14):3336–3349 González-Amuchastegui MJ, Serrano E (2015) Tufa buildups, landscape evolution and human impact during the Holocene in the Upper Ebro Basin. Quat Int 364:54–64 Gori A, Lin N, Xi D, Emanuel K (2022) Tropical cyclone climatology change greatly exacerbates US extreme rainfall–surge hazard. Nat Clim Change 12(2):171–178 Goudie AS, Viles HA (2016) Geomorphology in the Anthropocene. Cambridge University Press, Cambridge, p 324 Goudie AS, Viles HA, Pentecost A (1993) The late-Holocene tufa decline in Europe. Holocene 3:181–186 Gradziński M, Hercman H, Jaśkiewicz M, Szczurek S (2013) Holocene tufa in the Slovak Karst: facies, sedimentary environments and depositional history. Geol Q 57:769–788 Graf WL (1978) Fluvial adjustments to the spread of tamarisk in the Colorado Plateau region. Geol Soc Am Bull89(10):1491–1501 Graf WL (1981) Channel instability in a braided, sand bed river. Water Resour Res 17(4):1087–1094 Grano MC, Bishop P (2017) Barceló’s ‘missing water mills’ and Scottish and southern Italian horizontal mills. Vernacular Build 40:109–122 Grill G, Lehner B, Lumsdon AE, MacDonald GK, Zarfl C, Liermann CR (2015) An index-based framework for assessing patterns and trends in river fragmentation and flow regulation by global dams at multiple scales. Environ Res Lett 10(1):015001 Grill G et al (2019) Mapping the world’s free-flowing rivers. Nature 569:215–221 Gunnell Y, Krishnamurthy A (2003) Past and present status of runoff harvesting systems in dryland peninsular India: a critical review. Ambio 32(4):320–324 Gupta H, Kao SJ, Dai M (2012) The role of mega dams in reducing sediment fluxes: a case study of large Asian rivers. J Hydrol 464:447–458 Gurnell AM (1988) The hydrogeomorphological effects of beaver dam-building activity. Progr Phys Geogr 22(2):167–189 Gurnell A, Lee M, Souch C (2007) Urban rivers: hydrology, geomorphology, ecology and opportunities for change. Geogr Compass 1(5):1118–1137 Guzman O, Jiang H (2021) Global increase in tropical cyclone rain rate. Nat Commun 12(1):5344 Han S, Slater L, Wilby RL, Faulkner D (2022) Contribution of urbanisation to non-stationary river flow in the UK. J Hydrol 613:128417

107 Hawley RJ, MacMannis KR, Wooten MS (2013) Bed coarsening, riffle shortening, and channel enlargement in urbanizing watersheds, northern Kentucky, USA. Geomorphology 201:111–126 Hayhoe SJ, Neill C, Porder S, McHorney R, LeFebvre P, Coe MT, Krusche AV (2011) Conversion to soy on the Amazonian agricultural frontier increases streamflow without affecting stormflow dynamics. Global Change Biol 17:1821–1833 Heine K, Niller HP, Nuber T, Scheibe R (2005) Slope and valley sediments as evidence of deforestation and land-use in prehistporic and historic Eastern Bavaria. Z Geomorph Suppl 139:147–171 Hettler J, Irion G, Lehmann B (1997) Environmental impact of mining waste disposal on a tropical lowland river system: a case study on the Ok Tedi Mine, Papua New Guinea. Mineral Depos 32:280–291 Hoffman JD, Narumalani S, Mishra DR, Merani P, Wilson RG (2008) Predicting potential occurrence and spread of invasive plant species along the North Platte River, Nebruska. Invasive Plant Sci Manag 1(4):359–367 Hodgen MT (1939) Domesday water mills. Antiquity 13:261–279 Hoerling M, Barsugli J, Livneh B, Eischeid J, Quan X, Badger A (2019) Causes for the century-long decline in Colorado River flow. J Climate 32(23):8181–8203 Hohensinner S, Egger G, Muhar S, Vaudor L, Piégay H (2021) What remains today of pre-industrial Alpine rivers? Census of historical and current channel patterns in the Alps. River Res Appl 37(2):128–149 Holden J, Evans MG, Burt TP, Horton M (2006) Impact of land drainage on peatland hydrology. J Environ Quality 35(5):1764–1778 Hopkins KG, Morse NB, Bain DJ, Bettez ND, Grimm NB, Morse JL, Palta MM (2015) Type and timing of stream flow changes in urbanizing watersheds in the Eastern US. Elementa 3(1):000056 Horn JD, Fielding CR, Joeckel RM (2012) Revision of Platte River alluvial facies model through observations of extant channels and barforms, and subsurface alluvial valley fills. J Sed Res 82(2):72–91 Hornbeck JW, Pierce RS, Federer CA (1970) Streamflow changes after forest clearing in New England. Water Resour Res 6(4):1124–1132 Hoyle J, Brooks A, Brierley G, Fryirs K, Lander J (2008) Spatial variability in the timing, nature and extent of channel response to typical human disturbance along the Upper Hunter River, New South Wales, Australia. Earth Surf Proc Landf 33(6):868–889 Hubble TCT, Docker BB, Rutherford ID (2010) The role of riparian trees in maintaining riverbank stability: a review of Australian experience and practice. Ecol Eng 36(3):292–304 Huertas Herrera A, Lencinas MV, Toro Manríquez M, Miller JA, Martínez Pastur G (2020) Mapping the status of the North American beaver invasion in the Tierra del Fuego archipelago. PLoS ONE 15(4):e0232057 Hughes AO (2016) Riparian management and stream bank erosion in New Zealand. NZ J Marine Freshwater Res 50(2):277–290 Hughes RJ, Sullivan ME, Yok D (1991) Human-induced erosion in a highlands catchment in Papua New Guinea: the prehistoric and contemporary records. Z Geomorph Suppl 83:227–239 Hultine KR, Bush SE (2011) Ecohydrological consequences of nonnative riparian vegetation in the southwestern United States: a review from an ecophysiological perspective. Water Resour Res 47:W07542. https://doi.org/10.1029/2010WR010317 Hupp CR, Osterkamp WR (1996) Riparian vegetation and fluvial geomorphic processes. Geomorphology 14:277–295 Hupp CR, Noe GB, Schenk ER, Benthem AJ (2013) Recent and historic sediment dynamics along difficult run, a suburban Virginia Piedmont stream. Geomorphology 180:156–169 Huss M, Hock R (2018) Global-scale hydrological response to future glacier mass loss. Nat Clim Change 8(2):135–140 Ibáñez C, Day JW, Reyes E (2014) The response of deltas to sea-level rise: natural mechanisms and management options to adapt to high-end scenarios. Ecol Eng 65:122–130

108 Ibáñez C et al (2019) Basin-scale land use impacts on world deltas: human vs natural forcings. Glob Planet Change 173:24–32 Ibisate A et al (2016) Geomorphic monitoring and response to two dam removals: rivers Urumea and Leitzaran (Basque Country, Spain). Earth Surf Proc Landf 41(15):2239–2255 IPCC (Intergovernmental Panel on Climate Change) (2013) Climate Change 2013: the physical science basis: contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change. Cambridge University Press, Cambridge and New York Jaeger KL, Wohl E (2011) Channel response in a semiarid stream to removal of tamarisk and Russian olive. Water Resour Res 47(2):W02536. https://doi.org/10.1029/2009WR008741 James LA (2013) Legacy sediment: definitions and processes of episodically produced anthropogenic sediment. Anthropocene 2:16–26 James LA (2019) Impacts of pre-vs. postcolonial land use on floodplain sedimentation in temperate North America. Geomorphology 331:59–77 James LA, Beach TP, Richter DD (2020) Floodplain and terrace legacy sediment as a widespread record of anthropogenic geomorphic change. Ann Ass Am Geogr 111(3):742–755 Jasechko S, Seybold H, Perrone D, Fan Y, Kirchner JW (2021) Widespread potential loss of streamflow into underlying aquifers across the USA. Nature 591:391–395 Javadian M, Behrangi A, Sorooshian A (2019) Impact of drought on dust storms: case study over Southwest Iran.Environ Res Lett 14(12):124029 Jia M, Mao D, Wang Z, Ren C, Zhu Q, Li X, Zhang Y (2020) Tracking long-term floodplain wetland changes: A casestudy in the China side of the Amur River Basin. Int J Appl Earth Observ Geoinformation 92:102185 Joeckel RM, Henebry GM (2008) Channel and island change in the lower Platte River, Eastern Nebraska, USA: 1855–2005. Geomorphology 102(3–4):407–418 Jonell TN, Nave Calton I, Hurst MD, Jones P, Lucas AR, Naylor S (2023) Shaping landscapes and industry: linking historic watermill locations to bedrock river knickpoints. Scottish Geograph J. https://doi.org/10.1080/14702541.2023.2205853 Jones DB, Harrison S, Anderson K, Whalley WB (2019a) Rock glaciers and mountain hydrology: a review. Earth Sci Rev 193:66–90 Jones J et al (2019b) A comprehensive assessment of stream fragmentation in Great Britain. Sci Total Environ 673:756–762 Kahsay A et al (2023) Extent of Lake Tana’s papyrus swamps (1985– 2020), North Ethiopia. Wetlands 43(1):1–16 Kahraman A, Kendon EJ, Chan SC, Fowler HJ (2021) Quasi‐stationary intense rainstorms spread across Europe under climate change. Geophys Res Lett 48(13):e2020GL092361 Kemp DB, Sadler PM, Vanacker V (2020) The human impact on North American erosion, sediment transfer, and storage in a geologic context. Nat Commun 11(1):6012 Kincey M, Gerrard C, Warburton J (2022) Metals, mines and moorland: the changing lead mining landscapes of the North Pennines, UK, 1700–1948. Post-Medieval Archaeo l56(1):1–27 Kiss T, Nagy J, Fehérváry I, Vaszkó C (2019) (Mis) management of floodplain vegetation: the effect of invasive species on vegetation roughness and flood levels. Sci Total Environ 686:931–945 Knighton AD (1989) River adjustment to changes in sediment load: the effects of tin mining on the Ringarooma River, Tasmania, 1875–1984. Earth Surf Proc Landf 14(4):333–359 Knox JC (1977) Human impacts on Wisconsin stream channels. Ann Ass Am Geogr 67:323–342 Knox JC (1987) Historical valley floor sedimentation in the Upper Mississippi Valley. Ann Ass Am Geogr 77:224–244 Knox RL, Morrison RR, Wohl EE (2022a) Identification of artificial levees in the contiguous United States. Water Resour Res 58(4):e2021WR031308

4 Rivers Knox RL, Wohl EE, Morrison RR (2022b) Levees don't protect, they disconnect: a critical review of how artificial levees impact floodplain functions. Sci Total Environ:155773 Kondolf GM (1994) Geomorphic and environmental effects of instream gravel mining. Landsc Urban Planning 28(2–3):225–243 Kondolf GM, Rubin ZK, Minear JT (2014) Dams on the Mekong: cumulative sediment starvation. Water Resour Res 50(6):5158–5165 Knutson T et al (2020) Tropical cyclones and climate change assessment: Part II: projected response to anthropogenic warming. Bull Am Met Soc 101(3):E303–E322 Knutson TR, Chung MV, Vecchi G, Sun J, Hsieh TL, Smith AJ (2021) Climate change is probably increasing the intensity of tropical cyclones. Critical issues in climate change science. Science Brief Review. https://doi.org/10.5281/zenodo,4570334.169 Lang A (2003) Phases of soil erosion-derived colluviation in the loess hills of South Germany. CATENA 51:209–221 Lang OI, Mallia DV, Skiles SM (2023) The shrinking Great Salt Lake contributes to record high dust-on-snow deposition in the Wasatch Mountains during the 2022 snowmelt season. Environ Res Lett. https://doi.org/10.1088/1748-9326/acd409 Langdon J (1991) Water-mills and windmills in the West Midlands, 1086–1500. Econ Hist Rev 44:424–444 Lapp S, Byrne J, Townshend I, Kienzle S (2005) Climate warming impacts on snowpack accumulation in an alpine watershed. Int J Climatol 25(4):521–536 Lara A, Jones J, Little C, Vergara N (2021) Streamflow response to native forest restoration in former Eucalyptus plantations in south central Chile. Hydrol Proc 35(8):e14270 Larsen A, Larsen JR, Lane SN (2021) Dam builders and their works: beaver influences on the structure and function of river corridor hydrology, geomorphology, biogeochemistry and ecosystems. Earth Sci Rev 218:103623 Le Maitre DC, Versfield DB, Chapman RA (2000) The impact of invading alien plants on surface water resources in South Africa: a preliminary assessment. Water SA 26:397–408 Lemaitre-Basset T, Oudin L, Thirel G (2022) Evapotranspiration in hydrological models under rising CO2: a jump into the unknown. Clim Change 172(3–4). https://doi.org/10.1007/ s10584-022-03384-1 Li F, Lawrence DM (2017) Role of fire in the global land water budget during the twentieth century due to changing ecosystems. J Climate 30(6):1893–1908 Li T, Wang S, Liu Y, Fu B, Zhao W (2020) A retrospective analysis on changes in sediment flux in the Mississippi River system: trends, driving forces, and implications. J Soils Sediments 20(3):1719–1729 Limberger L, Silva MES, Pereira G, da Silva CF, Mataveli GAV, Lima BS (2021) Streamflow and precipitation trends in the Brazilian Amazon basin and their association with Pacific decadal oscillation and deforestation. Theor App Climatol 146(1):511–526 Limondin-Lozouet N, Preece RC, Antoine P (2013) The Holocene tufa at Daours (Somme Valley, northern France): malacological succession and palaeohydrological implications. Boreas 42:650–663 Lin Y, Wei X (2008) The impact of large-scale forest harvesting on hydrology in the Willow watershed of Central British Columbia. J Hydrol 359:141–149 Littell JS, McAfee SA, Hayward GD (2018) Alaska snowpack response to climate change: statewide snowfall equivalent and snowpack water scenarios. Water 10(5):668 Liu B, Wang N, Chen M, Wu X, Mo D, Liu J, Xu S, Zhuang Y (2017) Earliest hydraulic enterprise in China, 5100 years ago. Proc Nat Acad Sci 114(52):13637–13642 López-Moreno JI, Beguería S, García-Ruiz JM (2006) Trends in high flows in the central Spanish Pyrenees: response to climatic factors or to land-use change? Hydrol Sci J 51:1039–1050

References Luzón MA, Pérez A, Borrego AG, Mayayo MJ, Soria AR (2011) Interrelated continental sedimentary environments in the central Iberian Range (Spain): facies characterization and main palaeoenvironmental changes during the Holocene. Sed Geol 239:87–103 Maaß AL, Schüttrumpf H (2019) Elevated floodplains and net channel incision as a result of the construction and removal of water mills. Geogr Ann a, Phys Geogr 101(2):157–176 Macklin MG, Lewin J (1989) Sediment transfer and transformation of an alluvial valley floor: the River South Tyne, Northumbria. UK. Earth Surf Proc Landf 14(3):233–246 Macklin MG, Jones AF, Lewin J (2010) River response to rapid Holocene environmental change: evidence and explanation in British catchments. Quat Sci Rev 29:1555–1576 Macklin MG, Lewin J, Jones AF (2013) River entrenchment and terrace formation in the UK Holocene. Quat Sci Rev 76:194–206 Macklin MG, Lewin J, Jones AF (2014) Anthropogenic alluvium: an evidence-based meta-analysis for the UK Holocene. Anthropocene 6:26–38 Magilligan FJ, Graber BE, Nislow KH, Chipman JW, Sneddon CS, Fox CA (2016) River restoration by dam removal: enhancing connectivity at watershed scale. Elementa 4. https://doi.org/10.12952/ journal.elementa.000108 Majewski M (2014) Human impact on Subatlantic slopewash processes and landform development at Lake Jasień (northern Poland). Quat Int 324:56–66 Major JJ et al (2012) Geomorphic response of the Sandy River, Oregon, to removal of Marmot Dam. US Geological Survey, Reston, VA, p 64 Mallakpour I, Villarini G (2015) The changing nature of flooding across the central United States. Nat Clim Change 5(3):250–254 Marden M, Arnold G, Seymour A, Hambling R (2012) History and distribution of steepland gullies in response to land use change, East Coast Region, North Island, New Zealand. Geomorphology 153:81–90 Martin JT et al (2020) Increased drought severity tracks warming in the United States’ largest river basin. Proc Nat Acad Sci 117(21):11328–11336 Martínez-Fernández V, González del Tánago M, Maroto J, García de Jalón D (2017) Fluvial corridor changes over time in regulated and non-regulated rivers (Upper Esla River, NW Spain). River Res Appl 33(2):214–223 Martín-Vide JP, Ferrer-Boix C, Ollero A (2010) Incision due to gravel mining: modeling a case study from the Gállego River. Spain. Geomorphology 117(3–4):261–271 Martín-Vide JP et al (2023) Large wood debris that clogged bridges followed by a sudden release. The 2019 flash flood in Catalonia. J Hydrol Reg Stud 47:101348 Maselli V, Trincardi F (2013) Man made deltas. Sci Rep 3. https://doi. org/10.1038/srep01926 McPhillips L et al (2022) Learning from arid and urban aquatic ecosystems to inform more sustainable and resilient futures. J Hydrol 616:128841 Meisinger CL (1922) The streamflow experiment at Wagon Wheel Gap, Colorado. Science 55:622–624 Meyfroidt P, Lambin E (2009) Geographic and historical patterns of reforestation. Bull Séances Ac Roy Sci D’outre-Mer 55:477–502 Miller SA, Lyon SW (2021) Tile drainage causes flashy streamflow response in Ohio watersheds. Hydrol Proc 35(8):e14326 Miller JD, Kim H, Kjeldsen TR, Packman J, Grebby S, Dearden R (2014) Assessing the impact of urbanization on storm runoff in a peri-urban catchment using historical change in impervious cover. J Hydrol 515:59–70 Milly PC, Dunne KA (2020) Colorado River flow dwindles as warming-driven loss of reflective snow energizes evaporation. Science 367:1252–1255

109 Min S-K, Zhang X, Zwiers FW, Hegerl GC (2011) Human contribution to more-intense precipitation extremes. Nature 470:378–381 Miniat CF et al (2021) The Coweeta hydrologic laboratory and the Coweeta long-term ecological research project. Hydrol Proc 35(7):e14302 Morán-Tejeda E, López-Moreno JI, Stoffel M, Beniston M (2016) Rain-on-snow events in Switzerland: recent observations and projections for the 21st century. Clim Res 71(2):111–125 Mukherjee A, Bhanja SN, Wada Y (2018) Groundwater depletion causing reduction of baseflow triggering Ganges river summer drying. Sci Rep 8(1):12049 Musselman KN et al (2018) Projected increases and shifts in rain-onsnow flood risk over western North America. Nat Clim Change 8(9):808–812 Nanditha JS et al (2023) The Pakistan flood of August 2022: causes and implications. Earth’s Future 11(3):e2022EF003230 Najafi MR, Zwiers F, Gillett N (2017) Attribution of the observed spring snowpack decline in British Columbia to anthropogenic climate change. J Climate 30(11):4113–4130 Nayak RR, Krishnaswamy J, Vaidyanathan S, Chappell NA, Bhalla RS (2023) Invasion of natural grasslands by exotic trees increases flood risks in mountainous landscapes in South India. J Hydrol 617:128944 Napieralski JA, Carvalhaes T (2016) Urban stream deserts: mapping a legacy of urbanization in the United States. Appl Geogr 67:129–139 Navratil O, Breil P, Schmitt L, Grosprêtre L, Albert MB (2013) Hydrogeomorphic adjustments of stream channels disturbed by urban runoff (Yzeron River basin, France). J Hydrol 485:24–36 Naylor LA, Spencer T, Lane SN, Darby SE, Magilligan FJ, Macklin MG, Möller I (2017) Stormy geomorphology: geomorphic contributions in an age of climate extremes. Earth Surf Proc Landf 42(1):166–190 Neave M, Rayburg S, Swan A (2009) River channel change following dam removal in an ephemeral stream. Australian Geogr 40:235–246 Nichol SL, Augustinus PL, Gregory MR, Creese R, Horrocks M (2000) Geomorphic and sedimentary evidence of human impact on the New Zealand landscape. Phys Geogr 21:109–132 Nicod J (1986) Facteurs physico-chimiques de l’accumulation des formations travertineuses. Mediterranée 10:161–164 Notebaert B, Verstraeten G (2010) Sensitivity of West and Central European river systems to environmental changes during the Holocene: a review. Earth Sci Rev 103:163–182 Nury AH, Sharma A, Marshall L, Cordery I (2021) Modelling climate change impacts on the Brahmaputra streamflow resulting from changes in snowpack attributes. J Hydrol 603:126998 O’Briain R, Corenblit D, Gurnell A (2023) Interacting effects of climate change and invasions by alien plant species on the morphodynamics of temperate rivers. Wiley Interdisc Rev: Water:e1649 O’Hara SL, Street-Perrott FA, Burt TP (1993) Accelerated soil erosion around a Mexican highland lake caused by prehispanic agriculture. Nature 362:48–51 Ollero A (2010) Channel changes and floodplain management in the meandering middle Ebro River. Spain. Geomorphology 117(3–4):247–260 Otto FE et al (2023) Climate change increased extreme monsoon rainfall, flooding highly vulnerable communities in Pakistan. Environ Res: Climate 2(2):025001 Overpeck JT, Udall B (2020) Climate change and the aridification of North America. Proc Nat Acad Sci 117(22):11856–11858 Özpolat E, Demir T (2019) The spatiotemporal shoreline dynamics of a delta under natural and anthropogenic conditions from 1950 to 2018: a dramatic case from the Eastern Mediterranean. Ocean Coast Manag 180:104910

110 Page MJ, Trustrum NA (1997) A late Holocene lake sediment record of the erosion response to land use change in a steepland catchment, New Zealand. Z Geomorph 41:369–392 Pethick J, Orford JD (2013) Rapid rise in effective sea-level in southwest Bangladesh: Its causes and contemporary rates. Glob Planet Change 111:237–245 Pieruccini P, Susini D, Buonincontri MP, Bianchi G, Hodges R, Lubritto C, Di Pasquale G (2021) Late Holocene human-induced landscape changes in calcareous tufa environments in Central Mediterranean valleys (Pecora river, Southern Tuscany, Italy). Geomorphology 383:107691 Pizzuto J, O’Neal M (2009) Increased mid-twentieth century riverbank erosion rates related to the demise of mill dams, South River, Virginia. Geology 37:19–22 Poeppl RE, Keesstra SD, Hein T (2015) The geomorphic legacy of small dams—an Austrian study. Anthropocene 10:43–55 Pomeroy J, Fang X, Ellis C (2012) Sensitivity of snowmelt hydrology in Marmot Creek, Alberta, to forest cover disturbance. Hydrol Proc 26:1891–1904 Quang NH, Thang HN, Van An N, Luan NT (2023) Delta lobe development in response to changing fluvial sediment supply by the second largest river in Vietnam. CATENA 231:107314 Quintero F, Villarini G, Prein AF, Zhang W, Krajewski WF (2022) Discharge and floods projected to increase more than precipitation extremes. Hydrol Proc 36(11):e14738 Ramankutty N, Heller E, Rhemtulla J (2010) Prevailing myths about agricultural abandonment and forest regrowth in the United States. Ann Ass Am Geogr 100:502–512 Rasmussen P, Bradshaw EG (2005) Mid- to late-Holocene land-use change and lake development at Dallund S0, Denmark: study aims, natural and cultural setting, chronology and soil erosion history. Holocene 15:1105–1115 Rebelo AJ, Holden PB, Hallowes J, Eady B, Cullis JD, Esler KJ, New MG (2022) The hydrological impacts of restoration: a modelling study of alien tree clearing in four mountain catchments in South Africa. J Hydrol 610:127771 Reddy VR, Reddy MS, Palanisami K (2018) Tank rehabilitation in India: review of experiences and strategies. Agric Water Manag 209:32–43 Reid D, Church M (2015) Geomorphic and ecological consequences of riprap placement in river systems. J Am Water Resour Ass 51(4):1043–1059 Renaud FG, Syvitski JP, Sebesvari Z, Werners SE, Kremer H, Kuenzer C, Friedrich J (2013) Tipping from the Holocene to the Anthropocene: how threatened are major world deltas? Current Opinion Environ Sustain 5:644–654 Rets EP, Durmanov IN, Kireeva MB, Smirnov AM, Popovnin VV (2020) Past ‘peak water’ in the North Caucasus: deglaciation drives a reduction in glacial runoff impacting summer river runoff and peak discharges. Clim Change 163:2135–2151 Richardson CJ, Hussain NA (2006) Restoring the Garden of Eden: an ecological assessment of the marshes of Iraq. Bioscience 56(6):477–489 Richardson DM et al (2007) Riparian vegetation: degradation, alien plant invasions, and restoration prospects. Diversity Distrib 13:126–139 Richardson JM, Fuller IC, Holt KA, Litchfield NJ, Macklin MG (2014) Rapid post-settlement floodplain accumulation in Northland, New Zealand. CATENA 113:292–305 Robinson M (1990) Impact of improved land drainage on river flows. Institute of Hydrology, Wallingford, Report 113, p 226 Rogers S, Chen D, Jiang H, Rutherfurd I, Wang M, Webber M, Crow‐ Miller B, Barnett J, Finlayson B, Jiang M, ShiC (2020) An integrated assessment of China's South—North water transfer project. Geogr Res 58(1):49–63

4 Rivers Rollason E, Sinha P, Bracken LJ (2021) Interbasin water transfer in a changing world: a new conceptual model. Prog Phys Geogr 46:371–397 Rousi E, Selten F, Rahmstorf S, Coumou D (2021) Changes in North Atlantic atmospheric circulation in a warmer climate favor winter flooding and summer drought over Europe. J Clim 34(6):2277–2295 Roy S (2022a) Role of transportation infrastructures on the alteration of hillslope and fluvial geomorphology. Anthr Rev 9(3):344–378 Roy S (2022b) Impact of linear transport infrastructure on fluvial connectivity across the catchments of West Bengal, India. Geocarto Int 37(17):5041–5066 Roy S, Sahu AS (2017) Potential interaction between transport and stream networks over the lowland rivers in Eastern India. J Environ Manag 197:316–330 Rugel K, Jackson CR, Romeis JJ, Golladay SW, Hicks DW, Dowd JF (2012) Effects of irrigation withdrawals on streamflows in a karst environment: lower Flint River Basin, Georgia, USA. Hydrol Proc 26(4):523–534 Russell C, Waters CN, Himson S, Holmes R, Burns A, Zalasiewicz J, Williams M (2021) Geological evolution of the Mississippi River into the Anthropocene. Anthr Rev 8(2):115–140 Rutherford I (2000) Some human impacts on Australian stream channel morphology. In: Brizga S, Finlayson B (eds) River management: the Australasian experience. Wiley, Chichester, pp 11–49 Ryken N, Vanmaercke M, Wanyama J, Isabirye M, Vanonckelen S, Deckers J, Poesen J (2015) Impact of papyrus wetland encroachment on spatial and temporal variabilities of stream flow and sediment export from wet tropical catchments. Sci Total Environ 511:756–766 Rynne C (2009) Water-Power as a factor of industrial location in early Medieval Ireland: the environment of the early Irish water mill. Industr Archaeol Rev 31(2):85–95 Salmoral G, Willaarts BA, Troch PA, Garrido A (2015) Drivers influencing streamflow changes in the Upper Turia basin, Spain. Sci Total Environ 503:258–268 Sanders BF et al (2022) Large and inequitable flood risks in Los Angeles, California. Nat Sustain 6(1):47–57 Schelker J, Kuglerova L, Eklöf K, Bishop K, Laudon H (2013) Hydrological effects of clear-cutting in a boreal forest–snowpack dynamics, snowmelt and streamflow responses. J Hydrol 484:105–114 Schmitt RJP, Rubin Z, Kondolf GM (2017) Losing ground - scenarios of land loss as consequence of shifting sediment budgets in the Mekong Delta. Geomorphology 294:58–69 Schottler SP, Ulrich J, Belmont P, Moore R, Lauer J, Engstrom DR, Almendinger JE (2014) Twentieth century agricultural drainage creates more erosive rivers. Hydrol Proc 28:1951–1961 Scorpio V, Aucelli PP, Giano SI, Pisano L, Robustelli G, Rosskopf CM, Schiattarella M (2015) River channel adjustments in Southern Italy over the past 150 years and implications for channel recovery. Geomorphology 251:77–90 Segura-Beltrán F, Sanchis-Ibor C (2013) Assessment of channel changes in a Mediterranean ephemeral stream since the early twentieth century. The Rambla de Cervera, eastern Spain. Geomorphology 201:199–214 Seignemartin G, Mourier B, Riquier J, Winiarski T, Piégay H (2023) Dike fields as drivers and witnesses of twentieth-century hydrosedimentary changes in a highly engineered river (Rhône River, France). Geomorphology 431:108689 Serra-Llobet A, Kondolf GM, Magdaleno F, Keenan-Jones D (2022) Flood diversions and bypasses: benefits and challenges. Water 9(1):e1562 Sezen C, Šraj M, Medved A, Bezak N (2020) Investigation of rain-onsnow floods under climate change. Appl Sci 10(4):1242

References Shabalova MV, van Deursen WPA, Buishand TA (2003) Assessing future discharge of the river Rhine using regional climate model integrations and a hydrological model. Clim Res 23:233–246 Sharma R, Malaviya P (2021) Management of stormwater pollution using green infrastructure: the role of rain gardens. Water 8(2):e1507 Sheffield AT, Healy TR, McGlone MS (1995) Infilling rates of a steepland catchment estuary, Whangamata, New Zealand. J Coast Res 11:1294–1308 Sheng J, Wilson JP (2009) Watershed urbanization and changing flood behaviour across the Los Angeles metropolitan region. Nat Hazards 48:41–57 Shiferaw H, Alamirew T, Dzikiti S, Bewket W, Zeleke G, Teketay D, Schaffner U (2023) Water abstraction of invasive Prosopis juliflora and native Senegalia senegal trees: a comparative study in the Great Rift Valley Area. Ethiopia. Sci Total Environ 862:160833 Shiklomanov IA (1985) Large scale water transfers. In: Rodda JC (ed) Facets of hydrology II. Wiley, Chichester, pp 345–387 Siddik M, Bakar A, Dickson KE, Rising J, Ruddell BL, Marston LT (2023) Interbasin water transfers in the United States and Canada. Sci Data 10(1):1–9 Silveira L, Alonso J (2009) Runoff modifications due to the conversion of natural grasslands to forests in a large basin in Uruguay. Hydrol Proc 23:320–329 Sinha P, Rollason E, Bracken LJ, Wainwright J, Reaney SM (2020) A new framework for integrated, holistic, and transparent evaluation of inter-basin water transfer schemes. Sci Total Environ 721:137646 Siriwardena L, Finlayson BL, McMahon TA (2006) The impact of land use change on catchment hydrology in large catchments: the Comet River, Central Queensland, Australia. J Hydrol 326:199–214 Slater LJ, Villarini G (2017) Evaluating the drivers of seasonal streamflow in the US Midwest. Water 9(9):695 Smith HG, Sheridan GJ, Lane PN, Bren LJ (2011) Wildfire and salvage harvesting effects on runoff generation and sediment exports from radiata pine and eucalypt forest catchments, south-eastern Australia. Forest Ecol Manag 261:570–581 Snaddon CD, Wishart MJ, Davies BR (1998) Some implications of inter-basin water transfers for river ecosystem functioning and water resources management in southern Africa. Aquat Ecosyst Health Manag 1(2):159–182 Spate OHK, Learmonth ATA (1967) India and Pakistan. Methuen, London, p 877 Stanley DJ (1996) Nile delta: extreme case of sediment entrapment on a delta plain and consequent coastal land loss. Marine Geol 129:189–195 Surfleet CG, Tullos D (2013) Variability in effect of climate change on rain-on-snow peak flow events in a temperate climate. J Hydrol 479:24–34 Surian N, Rinaldi M (2003) Morphological response to riverengineering and management in alluvial channels in Italy. Geomorphology 50(4):307–326 Swank WT, Douglass JE (1974) Streamflow greatly reduced by converting deciduous hardwood stands to pine. Science 185:857–859 Syvitski JPM, Saito Y (2007) Morphodynamics of deltas under the influence of humans. Glob Planet Change 57:261–282 Syvitski JPM et al (2009) Sinking deltas due to human activities. Nat Geosci 2:681–686 Syvitski JP (2011) Global sediment fluxes to theEarth’s coastal ocean. Appl Geochem 26:S373–S374 Syvitski JPM et al (2020) Extraordinary human energy consumption and resultant geological impacts beginning around 1950 CE initiated the proposed Anthropocene Epoch. Comm Earth Environ 1(1):1–13

111 Syvitski J, Ángel JR, Saito Y, Overeem I, Vörösmarty CJ, Wang H, Olago D (2022) Earth’s sediment cycle during the Anthropocene. Nat Rev Earth Environ 3(3):179–196 Tockner K, Stanford JA (2002) Riverine flood plains: present state and future trends. Environ Conserv 29(3):308–330 Townsend-Small A, Pataki DE, Liu H, Li Z, Wu Q, Thomas B (2013) Increasing summer river discharge in southern California, USA, linked to urbanization. Geophys Res Lett 40:4643–4647 Trimble SW (1974) Man-induced soil erosion on the Southern Piedmont. Soil Conservation Society of America, Ankeny, p 180 Trimble SW (2003) Historical hydrographic and hydrologic changes in the San Diego Creek watershed, Newport Bay, California. J Hist Geogr 29:422–444 Trimble SW (2004) Effects of riparian vegetation on stream channel stability and sediment budgets. Water Sci Appl 8:153–169 Tuel A, El Moçayd N, Hasnaoui MD, Eltahir EA (2022) Future projections of High Atlas snowpack and runoff under climate change. Hydrol Earth System Sci 26(3):571–588 Tweel AW, Turner RE (2012) Landscape-scale analysis of wetland sediment deposition from four tropical cyclone events. PLoS ONE 7(11):e50528 Uribelarrea D, Pérez-González A, Benito G (2003) Channel changes in the Jarama and Tagus rivers (central Spain) over the past 500 years. Quat Sci Rev 22(20):2209–2221 Utsumi N, Kim H (2022) Observed influence of anthropogenic climate change on tropical cyclone heavy rainfall. Nat Clim Change 12(5):436–440 Van Manh N, Dung NV, Hung NN, Kummu M, Merz B, Apel H (2015) Future sediment dynamics in the Mekong Delta floodplains: impacts of hydropower development, climate change and sea level rise. Glob Planet Change 127:22–33 Verhage FY, Anten NP, Sentelhas PC (2017) Carbon dioxide fertilization offsets negative impacts of climatechange on Arabica coffee yield in Brazil. Clim Ch 144:671–685 Vita-Finzi C (1961) Roman dams in Tripolitania. Antiquity 35:14–20 Walker HJ, Coleman JM, Roberts HH, Tye RS (1987) Wetland loss in Louisiana. Geogr Ann 69A:189–200 Walsh RPD et al (2006) Changes in the spatial distribution of erosion within a selectively logged rainforest catchment in Borneo 1988–2003. In: Owens P, Collins A (eds) Soil erosion and sediment redistribution in river catchments: measurement, modelling and management. CABI, Wallingford, pp 239–253 Walter RC, Merritts DJ (2008) Natural streams and the legacy of water-powered mills. Science 319:299–304 Wang H, Saito Y, Zhang Y, Bi N, Sun X, Yang Z (2011) Recent changes of sediment flux to the western Pacific Ocean from major rivers in East and Southeast Asia. Earth Sci Rev 108:80–100 Warrick JA, Stevens AW, Miller IM, Harrison SR, Ritchie AC, Gelfenbaum G (2019) World’s largest dam removal reverses coastal erosion. Sci Rep 9(1):1–12 Wehrli M, Mitchell EA, van der Knaap WO, Ammann B, Tinner W (2010) Effects of climatic change and bog development on Holocene tufa formation in the Lorze Valley (central Switzerland). Holocene 20:325–336 Weisrock A (1986) Variations climatiques et periodes de sedimentation carbonatée a l’Holocene—l’age des depôts. Mediterranée 10:165–167 Wen F, Chen X (2006) Evaluation of the impact of groundwater irrigation on streamflow in Nebraska. J Hydrol 327:603–617 Westbrook CJ, Cooper DJ, Anderson CB (2017) Alteration of hydrogeomorphic processes by invasive beavers in southern South America. Sci Total Environ 574:183–190 Whitlow JR, Gregory KJ (1989) Changes in urban stream channels in Zimbabwe. Regulated Rivers Res Manag 4(1):27–42

112 Wieting C, Friedman JM, Rathburn S (2022) River channel response to invasive plant treatment across the American Southwest. Earth Surf Proc Landf. https://doi.org/10.1002/esp.5503 Winsemius HC et al (2016) Global drivers of future river flood risk. Nat Clim Change 6(4):381–385 Wohl E (2014) A legacy of absence: wood removal in US rivers. Progr Phys Geogr 38(5):637–663 Wohl E (2015) Legacy effects on sediments in river corridors. Earth Sci Rev 147:30–53 Wohl E, Merritts DJ (2007) What is a natural river? Geogr Compass 1:871–900 Wright SN, Thompson LM, Olefeldt D, Connon RF, Carpino OA, Beel CR, Quinton WL (2022) Thaw-induced impacts on land and water in discontinuous permafrost: a review of the Taiga Plains and Taiga Shield, northwestern Canada. Earth Sci Rev 232:104104 Xiao M, Udall B, Lettenmaier DP (2018) On the causes of declining Colorado River streamflows. Water Resour Res 54(9):6739–6756 Xi D, Lin N, Gori A (2023) Increasing sequential tropical cyclone hazards along the US East and Gulf coasts. Nat Clim Change 13(3):258–265 Yang X, Lu X (2014) Drastic change in China’s lakes and reservoirs over the past decades. Sci Rep 4. https://doi.org/10.1038/srep06041 Yang Q, Wang K, Zhang C, Yue Y, Tian R, Fan F (2011) Spatiotemporal evolution of rocky desertification and its driving forces in karst areas of Northwestern Guangxi, China. Environ Earth Sci 64:383–393 Yang HF et al (2018) Human impacts on sediment in the Yangtze River: a review and new perspectives. Glob Planet Change 162:8–17

4 Rivers Zaimes GN, Schultz RC (2015) Riparian land-use impacts on bank erosion and deposition of an incised stream in north-central Iowa, USA. CATENA 125:61–73 Zaimes GN, Tufekcioglu M, Schultz RC (2019) Riparian land-use impacts on stream bank and gully erosion in agricultural watersheds: what we have learned. Water 11(7):1343 Zektser S, Loáiciga HA, Wolf JT (2005) Environmental impacts of groundwater overdraft: selected case studies in the southwestern United States. Environ Geol 47:396–404 Zhang M, Wei X (2021) Deforestation, forestation, and water supply. Science 371:990–991 Zhang W et al (2022) Comparing the Yangtze and Mississippi River Deltas in the light of coupled natural-human dynamics: lessons learned and implications for management. Geomorphology 399:108075 Zhou Q (2014) A review of sustainable urban drainage systems considering the climate change and urbanization impacts. Water 6(4):976–992 Zipper SC et  al (2019) Cannabis and residential groundwater pumping impacts on streamflow and ecosystems in Northern California. Environ Res Comm 1(12):125005 Zolitschka B, Behre KE, Schneider J (2003) Human and climatic impact on the environment as derived from colluvial, fluvial and lacustrine archives—examples from the Bronze Age to the Migration period, Germany. Quat Sci Rev 22:81–100

5

The Cryosphere

Abstract

The cryosphere comprises snow,  sea ice, lake and river ice, icebergs, glaciers and ice caps, ice sheets, ice shelves, permafrost, and seasonally frozen ground. These phenomena are highly susceptible to climate change. This chapter concentrates on the disappearance of snowpack, disruption of permafrost and the formation of thermokarst, glacier retreat, and the formation of glacial lakes.

Keywords

Climate change · Glaciers · Periglacial · Permafrost · Snowpack · Thermokarst

5.1 Introduction The cryosphere is that portion of the Earth's climate system that includes solid precipitation, snow, sea ice, lake and river ice, icebergs, glaciers and ice caps, ice sheets, ice shelves, permafrost, and seasonally frozen ground. As with other environments, humans are creating changes, some of which are associated with climate change. The cryosphere may be especially susceptible to current warming (Bowden 2010) for a variety of reasons. Very importantly, in higher latitudes, the amount of temperature increase predicted is greater than the global mean, and this has been the case in recent decades. Secondly, the nature (e.g. rain rather than snow) and amount of precipitation may also change substantially. Thirdly, the northern limits of some very important vegetation zones, including boreal forest, taiga, and tundra, may shift latitudinally by hundreds of kilometres. Changes in snow cover and vegetation type may impact upon the state of permafrost because of their role in insulating the ground surface (Ling and Zhang 2003). In this

chapter we will look at three aspects of the cryosphere: snowpack disappearance; permafrost degradation and thermokarst development; and glacier retreat and the formation of glacial lakes.

5.2 Snowpack Disappearance As we saw in Sect. 2.9, present and future climatic warming will have a major influence on snow cover and snowpacks because of changes in how much precipitation falls as rain rather than snow, and how quickly snowpacks will melt in response to higher temperatures. This is illustrated dramatically when one compares images of a portion of Greenland at the same time of year (December) in 1988 compared to 2020 (Fig. 5.1). The difference is stark. For the western USA, predictions of future snowpack decline show regional variability, but in general indicate snowpack losses on the order of ~35 ± 10% by mid-century and ~50 ± 10% before the end of the twenty-first century (Siirila-Woodburn et al. 2021; Shrestha et al. 2021).

5.3 Permafrost Disruption and Thermokarst In high latitudes and at high altitudes some areas are underlain by permanently frozen subsoil—permafrost. It is an especially important control of a wide range of geomorphological processes and phenomena, including slope stability, ground subsidence, erosion rates, and stream runoff (see Sect. 4.13.8). Permafrost can be disturbed and degraded by human activities, and in the tundra ground subsidence is associated with thermokarst development, this being irregular, hummocky terrain produced by the melting of the permafrost. It is characterised by lakes and deranged drainage (Fig. 5.2). Ice wedge fissures may also degrade (Jorgenson et al. 2022).

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 A. Goudie, Landscapes of the Anthropocene with Google Earth, https://doi.org/10.1007/978-3-031-45385-4_5

113

114

5  The Cryosphere

Fig. 5.1  Google Earth images of changes in snow cover in part of Greenland between 1988 and 2020. Scale bar is 30 km. Location: 80° 51′ 45.55ʺ N, 25° 28′ 15.76ʺ W

Permafrost has been degraded by recent warming and lake formation has gone on apace (Farquharson et al. 2016, 2019; Lewkowicz and Way 2019). Along the Mackenzie Highway in Canada, between 1962 and 1988 the mean annual temperature rose by 1 °C and the southern fringe of

the discontinuous permafrost zone moved northwards by c 120 km (Kwong and Tau 1994). Jones et al. (2011) noted an expansion of lakes in the continuous permafrost zone of the Seward Peninsula and Olthof et al. (2015) described lake expansion in the Tuktoyaktuk Coastal Plain of north-west

5.3  Permafrost Disruption and Thermokarst

115

Fig. 5.2  Google Earth image of Drew Point thermokarst, Alaska, showing the aligned lakes and deranged drainage. Scale bar is 6 km. Location: 70° 50′ 36.05ʺ N, 153° 50′ 37.32ʺ W

Canada. However, as lakes expand the opportunity for drainage increases due to the encroachment towards a drainage gradient. Thus, total surface area of lakes in their study region declined by 15% due to the lateral drainage of several large lakes. In Alaska, in the discontinuous permafrost zone, complete thawing under a lake may lead to drainage integration. This causes the lake to be drained, thereby reducing their number (Yoshikawa and Hinzman 2003). Kirpotin et al. (2009) revealed that in Siberia, in the zone of continuous permafrost, thermokarst lakes expanded their areas by about 10–12% between 1973 and 2008, but that in the zone of discontinuous permafrost lake drainage prevailed, confirming observations made in Alaska. Sannel and Kuhry (2011) undertook studies in northern Canada, European Russia, and in northern Sweden and in their study the most extensive lateral expansion along lake margins from the mid-1970s to the mid-2000s occurred in large lakes (> 20,000 m2). They suggested that these are more likely to experience erosion as they have a longer fetch and thereby higher potential wave energy. They found that the maximum recorded lateral expansion rate was 7.3 m per decade in the Hudson Bay lowlands of Canada. The development of thermokarst lakes is not restricted to Arctic regions. It has also been described from the mountains of high Asia (Serban et al. 2021). In the Tibetan Plateau (Luo et al. 2022) an overall significant increase in thermokarst lake numbers (+158%) and surface areas (+ 123%) has

taken place over the last five decades. Webb and Liljedahl (2023) reviewed 139 sites from 57 studies of lake area change across northern permafrost regions, and this revealed that lake area is largely decreasing across the discontinuous permafrost zone, and in the continuous permafrost zone, the number of sites showing increasing lake area is nearly equal to the number of sites showing decreasing lake area. They suggested that lake area decline is probably a result of permafrost thaw, which promotes the formation of surface and subsurface drainage pathways that grow and accumulate across the landscape over time. The thawing of permafrost can also lead to rapid river bank erosion, as was recorded by Kanevskiy et al. (2015) in Alaska and by Fuchs et al. (2020) in the Lena Delta of Siberia. Accelerated permafrost melting was also implicated in slope destabilisation (Williams 1995) (see Sect. 9.8.7). With increasing exploitation of tundra areas in North America and Siberia for such activities as oil exploitation, there was inevitably an increasing interest in the problems caused by disturbance of the permafrost by human actions, such as forest clearance (Nicholas and Hinkel 1996), disturbance by construction and transport activity, and pipeline construction (Williams 1986). The movement of tracked vehicles has been particularly harmful to surface vegetation and deep rutting soon results from permafrost degradation. Similar effects may be produced by the siting of heated buildings on permafrost, by the laying of oil (Fig. 5.3), sewer

116

5  The Cryosphere

Fig. 5.3  Google Earth image of network of oil pipes and other installations in the permafrost at Prudhoe Bay, Alaska. Scale bar is 4 km. Location: 70° 14′ 30.66ʺ N, 148° 15′ 59.53ʺ W

and water pipes in or on the active layer, and by the installation of seismic lines (Williams et al. 2013).When surface vegetation is cleared for agricultural or constructional purposes the depth of thaw will tend to increase. Locally, global warming may promote more lightning strikes and fire occurrence, which can also contribute to permafrost degradation (Brown et al. 2015; Holloway et al. 2020; Chen et al. 2021). Attempts have been made to assess the future distribution of permafrost. On a Northern Hemisphere basis, Nelson and Anisimov (1993), in a pioneering study, calculated the areas of continuous, discontinuous, and sporadic permafrost for the year 2050. They indicated an overall reduction of 16% by that date. More recently, Yokohata et al. (2020) have predicted a global reduction of c 35%. For the Seward Peninsula in Alaska, Debolskiy et al. (2020) calculated that the near‐surface permafrost loss by the end of the century would be up to 43%. In Canada, Woo et al. (1992, p. 297) suggested that if temperatures rise by 4–5 °C, ‘Permafrost in over half of what is now the discontinuous zone could be eliminated’. An average northward displacement of the southern permafrost boundary by 150 ± 50 km would be expected for each 1 °C warming so that a total maximum displacement of between 1000 and 2000 km would be possible given the large amount of warming projected for these latitudes. Jin et al. (2000) attempted to model the response of permafrost to different degrees of temperature rise in the Tibetan Plateau region

and suggested that by the end of the twenty-first century, with a rise of 2.9 °C, the permafrost area would decrease by 58%. A more recent modelling exercise by Nie et al. (2021) predicted a decrease of up to 42%. In Chile, Pereira et al. (2021) estimated that the permafrost area in this region will decrease between 13 and 87% by the end of the century.

5.4 Valley Glaciers and Small Ice Caps The world’s alpine or mountain glaciers are numerous, and in all there are probably over 160,000 on the face of Earth. They are sensitive to climate change, and we have many examples of changes in glacier length since the end of the Little Ice Age (LIA) in the mid to late nineteenth century (Oerlemans et al. 1998). The rate of retreat has not been constant, or the process uninterrupted, and some glaciers have shown a tendency to advance for some of the period. In the case of the more active example rates of retreat can often be very high, being of the order of 20 to 70 m per year over extended periods of some decades. It is therefore common to find that over the last hundred or so years alpine glaciers in many areas have retreated by some km (Fig. 5.4). Writing in 1996, Fitzharris (p. 246) looked at how glaciers had performed since the end of the LIA in various mountain regions. For the European Alps he suggested that the glaciers had lost about 30–40% of their surface area and about 50% of

5.4  Valley Glaciers and Small Ice Caps

117

Fig. 5.4  Google Earth images of valley glaciers in southern Chile, showing the retreat between 2003 and 2020. Note the formation of a new glacial lake by 2020. Scale bar is 8 km. Location: 51° 15′ 49.83ʺ S, 73° 32′ 18.79ʺ W

their ice volume. In North America glaciers had also shown a general retreat after the LIA maximum, particularly at lower elevations and southern latitudes. In the Rocky Mountains the area lost was about 25%. In the case of China’s monsoonal

temperate glaciers they had lost an amount equivalent to 30% of their modern glacier area. New Zealand glaciers had lost between one quarter and almost half of their volume between the LIA maximum and the 1970s.

118

Not all glaciers have retreated in recent decades but many have. These changes are expressed in terms of their mass balance, which is defined as the difference between gains and losses (expressed in terms of water equivalent). The World Glacier Monitoring Service (WGMS) has suggested that globally the average annual mass loss of glaciers during the warming decade from 1996 to 2005 was twice that of the previous decade (1986–1995) and over four times that from 1976 to 1985. The WGMS has also illustrated the global picture of glacier retreat (https://wgms.ch/ global-glacier-state/) (Accessed 8th June 2023). Trends vary between regions, but the overall picture of retreat is clearly demonstrated (see Fig. 5.5). That said, the tempo of glacier change can be variable. This can be illustrated for Scandinavian glaciers. The positive mass balance (and advance) of some of these notwithstanding rising temperatures has been attributed to increased storm activity and precipitation inputs coincident with a high index of the North Atlantic Oscillation (NAO) in winter since 1980 (Nesje et al. 2000). However, since 2000, the Norwegian glaciers, which were still advancing in the 1990s, have started to retreat at a rapid rate, though with interruptions (Andreassen et al. 2020). If retreat continues, then by 2100, Nesje et al. (2008) calculated that about 98% of Norwegian glaciers are likely to disappear and that their area may be reduced by around a third. A positive mass balance phase in the Austrian Alps between 1965 and 1981 has been correlated with a negative NAO index (Schöner et al., 2000). Marine-terminating or tidewater glaciers (i.e. glaciers that drain directly into the ocean) can retreat very speedily and appear to be relatively unstable (Vieli 2021). Venteris (1999) gave rates of more than 1 km per year. Such rapid retreat is accomplished by iceberg calving, with icebergs detaching from glacier termini when the ice connection is no longer able to resist either the upward force of flotation and/or the downward force of gravity. Certainly, calving permits larger volumes of ice to be lost to the glacier than would be possible through surface ablation alone. For the Greenland ice sheet, calving, together with submarine melting at the ice-ocean contact, accounts for approximately 50% of wasting, and for the Antarctic ice sheet, it is close to 90% (van der Ween 2002). The rapid retreat is favoured by the thinning of ice near the termini, its flotation and its weakening by bottom crevasses. Increased melting of the submerged parts of these glaciers by warming ocean waters is thought to be another important driver of this retreat (Cowton et al. 2019; Jackson et al. 2020). Tidewater glaciers on the Antarctic Peninsula have been retreating and thinning fast (Pritchard and Vaughan 2007) as they have in Spitzbergen (Kavan et al. 2022). The Columbia tidewater glacier (Fig. 5.6) in Alaska is perhaps the most famous case of all. It began rapidly losing

5  The Cryosphere

ice during the early 1980s. Since that time, it has retreated more than 20 km and lost 50% of its volume (https://earthobservatory.nasa.gov/world-of-change/ColumbiaGlacier) (Accessed 8th June 2023), while the Mendenhall Glacier, which calves into a proglacial lake, displayed 3 km of terminus retreat in the twentieth century (Motyka et al. 2002). Not all Alaskan tidewater glaciers have been retreating, however, and the Hubbard Glacier has been advancing for a century (https://pubs.usgs.gov/fs/fs-001-03/fs-001.03.pdf) (Accessed 8th June 2023). Kochtitzky and Copland (2022) reviewed measurements of 1704 tidewater glaciers in the Northern Hemisphere for 2000, 2010, and 2020, including the Greenland Ice Sheet, to provide the first complete measure of their variability. 123 glaciers became no longer marine-terminating over this period, and overall, 85.3% of glaciers retreated, 2.5% advanced, and the remaining 12.3% did not change outside of uncertainty limits. Many high-altitude glaciers in the mountains of the tropics have also displayed fast rates of decay over the last hundred years or so, to the extent that some of them now only have around one-sixth to one-third of the area they had at the end of the nineteenth century (Kaser 1999). Due to their relatively small size compared to polar ice sheets, the climatic warming since the mid-twentieth century has had devastating effects on these types of glacier. Veettil and Kamp (2019), Thompson et al. (2021), and Knight (2023) surveyed the changes that have taken place in recent decades, and these are some of their findings: The glacier area in Venezuela decreased from 2.03 to 0.29 km2 (85.7%) between 1952 and 2003, and then to around 0.1 km2 in 2011. For Colombia, a glacier area reduction of 50% between the 1950s and 2000 was estimated; the total glacial area was estimated to be 109 km2 for the 1970s, 55.4 km2 in the 2000s, and 36.8 km2 in 2015. In Peru, between 1987 and 2010, glaciers in the entire Cordillera Blanca lost 25% in area. Glaciers in the Cordillera Vilcanota lost up to around 4 km2 annually between 1988 and 2012. An even greater area loss was observed in the Cordillera Carabaya, where the glacial area decreased by 86% from 1975 to 2015. In Peru, the surface area of the Quelccaya ice cap decreased by 46% between 1976 and 2020. In Peru, the Incachiriasca Glacier showed a loss of 51.4% of the glacier’s total area: from 0.528 km2 (1975) to 0.257 km2  (2018), equivalent to − 0.0063 km2 1 −1 yr−  (1.2% yr ). The annual rate of decline has increased considerably, especially since 2010, from 1% in 2001–2010 to 3% in 2010–2018 (Navarro et al. 2023). Mt Kenya’s glaciers retreated dramatically between 1963 and 1987 and further to 1998, when the glacial area had

5.4  Valley Glaciers and Small Ice Caps

119

Fig. 5.5  Changes in glacier mass balance from 1950 to 2022 (modified from: https://wgms.ch/ global-glacier-state/) (Accessed 8th June 2023). Public domain through Creative Commons

been reduced to 0.4 km2. Glacier area loss was 15.2% from 1987 to 1993, 31% from 1993 to 2004, and 40% from 2004 to 2015, indicating an accelerating glacier recession. On Mt Kilimanjaro, the glacial area decreased from 6.7 km2 to 3.3 km2 between 1953 and 1989, to 2.6 km2 in 2000 and to 1.7 km2 in 2016. In 1880 its glaciated area had been 20 km2.

The total glaciated area in the Ruwenzori Mountains declined from around 2 km2 in 1987 to around 1 km2 in 2003, and to zero by 2023. In Papua in the early 1970s the glaciated area was 7.5 km2. The area decreased from 3.85 km2 in 1988 to 0.58 km2 in 2015, which is a decrease of 85%.

120

5  The Cryosphere

Fig. 5.6  Google Earth images of the Columbia tidewater glacier, Alaska, in 1990 and 2020. Scale bar is 10 km. Location: 61° 3′ 32.13ʺ N, 147° 0′ 46.63ʺ W

The reasons for the retreat of the East African glaciers include not only an increase in temperature, but also a relatively dry phase since the end of the nineteenth century (which led to less accumulation of snow) and a reduction in cloud cover, which led to more ablation (Molg et al. 2003).

Glaciers in the Himalaya–Karakoram mountain ranges harbour approximately half of the ice volume in Highmountain Asia and modulate the flow of freshwater to almost 869 million people within the Indus, Tarim, Ganga, and Brahmaputra river basins. Their changing state is

5.4  Valley Glaciers and Small Ice Caps

therefore of great significance. The recent response of these Asian glaciers shows great regional variations which depend on the amount of debris cover that occurs on their surfaces (Ali et al. 2017) and also on differing precipitation trends (Yao et al. 2007). In the west of the region, around

121

half of the westerlies-influenced Karakoram glaciers have been advancing or have been stable, showing a slight positive mass balance in recent years (Gardelle et al. 2012; Bahuguna et al. 2021), though this seems to be changing (ICIMOD 2023). The same is true of the western Kun Lun

Fig. 5.7  Google Earth images of the advancing snout of the Hassanabad Glacier, northern Pakistan, between 2006 (top) and 2022 (bottom). Scale bar is 2 km. Location: 36° 20′ 43.29ʺ N, 74° 34′ 48.28ʺ E

122

and the north-western Himalayas (Muhammad et al. 2019). In northern Pakistan, the Hassanabad Glacier advanced between 2006 and 2022 (Fig. 5.7).This has been called ‘the Karakoram anomaly’ because it contrasts with glacier retreat worldwide (Minora et al. 2013; Farinotti et al. 2020). It is caused by a recent increase in winter monsoonal snowfall (Dimri 2021), some local cooling, and the effects of thick debris mantles on some glaciers (Qureshi et al. 2017). The Karakoram glaciers are also known for their propensity to surge (Paul 2020), and this includes the Hassanabad Glacier (Bhambri et al. 2017). However, moving eastwards, the great bulk of the monsoon-influenced glaciers in the central Himalaya have been retreating and losing mass because of rising temperatures and decreasing precipitation at high altitudes, especially those with a limited debris cover (Scherler et al. 2011). Indeed, glaciers in the central Himalaya exhibit some of the fastest retreat rates on Earth (Norris et al. 2019). These are some of the findings of recent research on Asian mountain glaciers: Zhu et al. (2014), working on the Naimona’Nyi glaciers in the western Himalaya shows that the glacier retreat rate between 2003 and 2013 was five times of that in the previous 30 years (1973 to 2003) Nurakynov et al. (2023) found that in the Zhetysu Alatau Range (Tien Shan). The total glacier area decreased by 49 ± 2.8% or by 399 ± 11.2 km2 from 813.6 ± 22.8 km2 to 414.6 ± 11.6 km2 during 1956–2016 Since the early twentieth century, glaciers on the Tibetan Plateau have generally been retreating, and this trend has accelerated since the 1990s. In the central part, glaciers lost 22% of their coverage from 1977 to 2010 (Wang et al. 2013) In the Chinese Altai Mountains, analyses by Wang et al. (2015) showed that the collective area of all 201 glaciers investigated was reduced by 30.4% from 1959 to 2008. Fifty-five glaciers disappeared entirely. The rate of loss has slowed since (Wang et al. 2023) Glacier area is estimated to have decreased by 20–25% in the Tien Shan, 30–35% in the Pamirs, and 50% in northern Afghanistan during the twentieth century. For the second part of the century, glacier area loss for the Polar Urals was 22.3% (Khromava et al. 2014) In the Caucasus Mountains the mean rate of glacier mass loss has accelerated from 0.42 ± 0.61 m of water equivalent per year between 2000 and 2010, to 0.64 ± 0.66 m w.e. per year between 2010 and 2019 (Tielidze et al. 2022a). Glacier mass loss was nearly 4 times higher in 2000–2020 than it was between 1911 and 1960 (Tielidze et al. 2022b) Nie et al. (2021) suggested that it is likely that only 32% of the glacier area in the Himalayas will remain by the end of the twentieth century Li and Xu (2023) found that in western China from 2000 to 2020, the glaciers in western China showed a retreating trend overall, with the area reduced by 15,575 km2 and an average area retreat rate of 1.46%/a. During this period, from 2000 to 2010, the glacier area decreased by 9848 km2, with an average shrinkage rate of 1.26%/a. From 2010 to 2020, the glacier area decreased by 5728 km2 with a rate of 1.85%/a

5  The Cryosphere ICIMOD (2023, p. xiii) reporting on the situation in the whole Hindu Kush and Himalayan system, stated ‘Glacier mass balance has become increasingly negative, with rates increasing from – 0.17 m w.e. per year from 2000–2009 to – 0.28 m w.e. per year from 2010–2019, suggesting an acceleration in mass loss. The most negative mass balances are observed in the eastern part of the HKH within the Southeast Tibet and Nyainqêntanglha regions showing – 0.78 ± 0.10 m w.e. per year for 2010–2019, while the West Kunlun region shows a near-balanced mass budget of – 0.01 ± 0.04 m w.e. per year. The Karakoram region, known previously for balanced regional mass balances, showed a slight wastage of – 0.09 ± 0.04 m w.e. per year for 2010–2019. These results indicate moderate mass loss of the Karakoram glaciers, especially post-2013 and suggest that the Karakoram Anomaly—anomalous behaviour of glaciers in the Karakoram, showing stability or even growth—has probably come to an end’

In New Zealand the situation is complex. Length change records for Franz Josef and Fox Glaciers demonstrate that these glaciers have lost ~3 km in length and at least 3–4 km2 in area since the 1800s (Purdie et al. 2014), with the greatest overall loss occurring between 1934 and 1983. Within this dramatic and ongoing retreat, however, both glaciers have experienced periods of re-advance (Purdie et al. 2021) and Mackintosh et al. (2017) related this to local cooling rather than to any increase in precipitation. Looking at a larger sample of glaciers, Chinn et al. (2012) showed that estimated ice volume (in water equivalents) for the Southern Alps had decreased from 54.5 km3 in 1976 to 46.1 km3 by 2008, a loss of 15% of the total ice volume. Carrivick et al. (2020) determined volume changes for 400 mountain glaciers across the Southern Alps for three time periods; (i) pre-industrial “Little Ice Age (LIA)” to 1978, (ii) 1978 to 2009, and (iii) 2009 to 2019. At least 60 km3 ± 12 km3 or between 41 and 62% of the Little Ice Age total ice volume has been lost. The rate of mass loss has nearly doubled from − 0.4 m w.e (water equivalent) per year during 1600 to 1978 to − 0.7 m w.e per year at present. Anderson et al. (2021) predict that in the Southern Alps a reduction of 50–92% in glacier cover relative to present day will occur by the end of the century. One fascinating possible result of ice cap wastage is enhanced tectonic activity as a result of changes in the loading on the Earth’s crust (McGuire 2012). Such tectonic deformation has been detected in Patagonia (Lenzano et al. 2023).

5.5 Glacial Lakes One of the most dynamic and apparent impacts of a warming climate is the expansion of glacial lakes (Sattar et al. 2022; Steffen et al. 2022). From time to time these may drain catastrophically to give outburst floods. Some lakes

5.5  Glacial Lakes

develop behind moraine dams, which consist of unconsolidated sediments that were typically deposited along a steep ice front that recently melted away and are thus highly unstable. Dam failures can also be triggered by thawing permafrost or by displacement waves from rockfall, ice avalanches or ice calving. The resulting sudden and often catastrophic discharge of water characteristically transforms into large debris flows. Hence, glacial lake outburst floods (GLOFs) are among the most dangerous natural hazards in high mountain areas and pose an immense threat to people and infrastructures regionally (Furian et al. 2021). There are many examples of accelerating lake formation. Working on a 1300 km length of ice margin in western Greenland, Carrivick and Quincey (2014) used remotely sensed imagery for the period from 1987 to 2010. They discovered that there had been a c 44% net increase in the number of lakes, and a c 20% expansion in total lake surface area. Lakes have also developed in Switzerland (Mölg et al. (2021), Norway (Laute and Beylich 2020), and Arctic Sweden (Dye et al. 2022). Similarly, in the Tibetan Plateau, from 1986 and 2001 the total number of lakes increased by 11% and the total lake surface areas increased by 47%. Glacial lakes also expanded in the Mount Everest area (Benn et al. 2012), on the border between Bhutan and China (Komori 2008), and in the Eastern Himalayas (Veh et al. 2020; Zheng et al. 2021) (Fig. 5.8). Zhang et al (2023) estimated the volume change of glacial lakes across the greater Himalaya. They

123

showed that proglacial lakes have increased 47% by number, 33 ± 2% by area and 42 ± 14% by volume from 2000 to 2020. In Peru there is a good data set on glacier lake development (Emmer et al. 2020), and in the Peruvian Andes, Vilimek et al. (2005) showed that following rapid deglaciation the volume of Palcacocha Lake increased from 514,800 m3 in 1972 to 3,690,000 m3 in 2003 (Fig. 5.9), and this expansion continues to pose hazards associated with potential outburst floods (Stuart-Smith et al. 2021). Further south, in Patagonia, Mölg (2014) found that between 1985 and 2011 the number of proglacial lakes increased from 223 to 327 and their area expanded by 59%. Updated data in de Vries et al. (2023) shows that this trend has continued. Carrivick et al. (2022) have discussed recent and future proglacial lake development in New Zealand. On a global basis, Taylor et al. (2023) report that since 1990, the number, area, and volume of glacial lakes globally has grown rapidly, increasing by 53%, 51%, and 48% respectively, but that the greatest threat is posed to the people living in the mountains of High Asia, as in Bhutan (Rinzin et al. 2023).

5.6 Polar Ice Sheets and Ice Caps The state of the polar ice sheets and ice caps is a matter of great interest because of their crucial role in determining global sea-level rise. In the case of Greenland Ice Sheet,

Fig. 5.8  Google Earth image of glacial lakes produced following glacial retreat in Lunana, Bhutan. Scale bar is 3 km. Location: 28° 6′ 48.80ʺ N, 90° 15′ 43.30ʺ E. Details of this site and its history are given in Ageta et al. (2000) and in Rinzin et al. (2023)

124

5  The Cryosphere

Fig. 5.9  Google Earth image of the greatly expanded glacial lake at Palcacocha in Peru. Scale bar is 800 m. Location: 9° 23′ 37.01ʺ S, 77° 22′ 36.42ʺ W

Mouginot et al. (2019) reconstructed its mass balance. They found that the decadal mass balance switched from a mass gain of + 47 ± ± 21 Gt per year in 1972–1980 to a loss of 51 ± ± 17 Gt per year in 1980–1990. Thereafter the mass loss increased from 41 Gt per year in 1990–2000, to 187 Gt per year in 2000–2010, and to 286 Gt per year in 2010–2018—a six-fold since the 1980s and an average of 80 Gt/y per decade. Over the last 30 years both ablation and discharge have increased significantly, while snowfall has not (Gregory et al. 2020). Around half of the ice loss was due to increased surface runoff (Imbie Team 2020), while the increase in glacier discharge was probably the icedynamical response of outlet glaciers to reduced buttressing by their ice tongues, which have thinned due to basal melting by warmer seawater. In that connection, Rignot et al. (2021) and Wood et al. (2021) have pointed to the important role of enhanced intrusion of warm Atlantic Waters (AW) into fjords. Ice streams have speeded up (Khan et al. 2022). There have also been great declines in Arctic sea ice cover, and these are running at 6.22% per decade (Cai et al. 2021). Johannessen and Shalina (2023) found that during the period 1979–2022, the mean September (summer minimum) sea ice extent has decreased dramatically, by 39.7%, while in March (winter maximum) it has decreased by 11.8% and annually by 18.2%. There have also been changes in the extent of what is called fast ice. For example, because of the low air

temperature and the highly indented coastline, the coastal waters of Svalbard are covered every year by ice that holds fast to the coastline or the sea bottom. It usually accumulates in fjords, between islands, and in shallow inshore waters. In the Arctic, fast ice is biologically significant as a breeding and moulting site for seals, mainly ringed seals (Pusa hispida), which are the principal prey of polar bears (Ursus maritimus). Moreover, fast ice protects coastal areas from erosion by wave action for as long as it persists, and may also provide a barrier against permafrost melting. Urbański and Litwicka (2022) found that on average, the minimum two-monthly extent of land-fast sea ice along the Svalbard coast was about 12,000 km2 between 1973 and 2000. However, in 2005–2019, the fast ice extent halved to about 6000 km2. They believed that a further increase in mean winter air temperatures by two degrees, which could occur in the next 10–20 years, could result in a minimum two-monthly land-fast ice extent of only about 1500 km2. Fast ice wastage has also been found for other areas, such as the Laptev Sea in the Russian Arctic (Selyuzhenok et al. 2015). In Antarctica, changes in ocean heat content linked to changes in Southern Hemisphere atmospheric conditions have enhanced basal melting of ice shelves, causing them to shrink. Ice shelves are thick, floating platforms of ice ranging from  1500 m in thickness, and are formed where glaciers or ice sheets flow on to the ocean. Floating ice shelves fringe 74% of Antarctica's coastline.

References

Observations over the past 60 years indicate that a number of ice shelves around Antarctica have been rapidly thinning, retreating, and collapsing, particularly in West Antarctica and the Antarctic Peninsula.. Rising atmospheric and oceanic temperatures, which cause shelf thinning and melting, act with wind forcing and upwelling to increase the retreat of ice shelves and to facilitate crevasse formation and propagation, ultimately leading to calving events (Ingels et al. 2021; Hogg and Gudmundsson 2017). This reduction in some shelves has reduced their buttressing capability and has led to increased ice discharge into the Southern Ocean (Smith et al. 2020), though in Eastern Antarctica some shelves have been advancing (Andreasen et al. 2023). Rignot et al. (2019) observed that the Antarctic ice sheet has been losing mass along its periphery due the enhanced flow of its glaciers, at a rate that has been increasing over time, while there has been no long-term trend change in snowfall accumulation in the interior. The total mass loss increased from 40 Gt per year in 1979–1990 to 50 Gt per year in 1989–2000, 166 Gt per year in 1999–2009, and 252 Gt per year in 2009–2017, a more than six-fold increase over the period. Glacer retreat in parts of West Antarctica has been rapid (Milillo et al. 2019, 2022).

5.7 Conclusion It is a truism that the cryosphere is highly dependent on temperature. It is, therefore, not surprising that its components are especially sensitive to global heating. Moreover, because of the importance of glaciers and ice caps for controlling global sea levels, the melting of ice has implications all over the world, especially in the coastal lowlands where such a large proportion of Earth’s human population lives. This is a matter that will be returned to in the next chapter. It is not only sea-level rise that has global implications. Changes in albedo as snow and ice disappear, and the release of the greenhouse gas methane as permafrost melts, will have global climatic consequences.

References Ageta Y, Iwata S, Yabuki H, Naito N, Sakai A, Chiyuke N, Karma T (2000) Expansion of glacier lakes in recent decades in the Bhutan Himalayas. IAHS Publ 264:165–176 Ali I, Shukla A, Romshoo SA (2017) Assessing linkages between spatial facies changes and dimensional variations of glaciers in the upper Indus Basin, western Himalaya. Geomorphology 284:115–129 Anderson B et al (2021) Modelled response of debris-covered and lake-calving glaciers to climate change, Kā Tiritiri o te Moana/ Southern Alps, New Zealand. Glob Planet Change 205:103593 Andreassen LM, Elvehøy H, Kjøllmoen B, Belart JM (2020) Glacier change in Norway since the 1960s–an overview of mass balance, area, length and surface elevation changes. J Glaciol 66:313–328

125 Andreasen JR, Hogg AE, Selley HL (2023) Change in Antarctic ice shelf area from 2009 to 2019. Cryosphere 17(5):2059–2072 Bahuguna I, Rathore BP, Jasrotia AS, Randhawa SS, Yadav SKS, Ali S, Gauta, N, Poddar J, Srigyan M, DhanadeA, Joshi P (2021) Recent glacier area changes in Himalaya–Karakoram and the impact of latitudinal variation.Current Sci 121(7):929 Benn DI et al (2012) Response of debris-covered glaciers in the Mount Everest region to recent warming, and implications for outburst flood hazards. Earth Sci Rev 114:156–174 Bhambri R, Hewitt K, Kawishwar P, Pratap B (2017) Surge-type and surge-modified glaciers in the Karakoram. Sci Rep 7(1):15391 Bowden WB (2010) Climate change in the Arctic—Permafrost, thermokarst, and why they matter to the non-Arctic world. Geogr Compass 4:1553–1566 Brown DR et al (2015) Interactive effects of wildfire and climate on permafrost degradation in Alaskan lowland forests. J Geophys Res: Biogeosciences 120(8):1619–1637 Cai Q, Wang J, Beletsky D, Overland J, Ikeda M, Wan L (2021) Accelerated decline of summer Arctic sea ice during 1850–2017 and the amplified Arctic warming during the recent decades. Environ Res Lett 16(3):034015 Carrivick JL, Quincey DJ (2014) Progressive increase in number and volume of ice-marginal lakes on the western margin of the Greenland Ice Sheet. Glob Planetary Change 116:156–163 Carrivick JL, James WH, Grimes M, Sutherland JL, Lorrey AM (2020) Ice thickness and volume changes across the Southern Alps, New Zealand, from the little ice age to present. Sci Rep 10(1):1–10 Carrivick JL et al (2022) Coincident evolution of glaciers and icemarginal proglacial lakes across the Southern Alps, New Zealand: Past, present and future. Glob Planet Change 211:103792 Chen Y, Chang Z, Xu S, Qi P, Tang X, Song Y, Liu D (2021) Altitudinal gradient characteristics of spatial and temporal variations of snowpack in the Changbai Mountain and their response to climate change. Water 13(24):3580 Chinn T, Fitzharris BB, Willsman A, Salinger MJ (2012) Annual ice volume changes 1976–2008 for the New Zealand Southern Alps. Glob Planet Change 92:105–118 Cowton TR, Todd JA, Benn DI (2019) Sensitivity of tidewater glaciers to submarine melting governed by plume locations. Geophys Res Lett 46(20):11219–11227 Debolskiy MV, Nicolsky DJ, Hock R, Romanovsky VE (2020) Modeling present and future permafrost distribution at the Seward Peninsula, Alaska. J Geophys Res: Earth Surf 125(8):e2019JF005355 de Vries MV, Romero M, Penprase SB, Ng GH, Wickert AD (2023) Increasing rate of 21st century volume loss of the Patagonian Icefields measured from proglacial river discharge. J Glaciol 14. https://doi.org/10.1017/jog.2023.9 Dimri AP (2021) Decoding the Karakoram anomaly. Sci Total Environ 788:147864 Dye A, Bryant R, Rippin D (2022) Proglacial lake expansion and glacier retreat in Arctic Sweden. Geogr Ann: Series a, Phys Geogr 104:268–287 Farinotti D, Immerzeel WW, de Kok RJ, Quincey DJ, Dehecq A (2020) Manifestations and mechanisms of the Karakoram glacier Anomaly. Nat Geosci 13(1):8–16 Farquharson LM, Mann DH, Grosse G, Jones BM, Romanovsky VE (2016) Spatial distribution of thermokarst terrain in Arctic Alaska. Geomorphology 273:116–133 Farquharson LM, Romanovsky VE, Cable WL, Walker DA, Kokelj SV, Nicolsky D (2019) Climate change drives widespread and rapid thermokarst development in very cold permafrost in the Canadian High Arctic. Geophys Res Lett 46(12):6681–6689 Fitzharris B (1996) The cryosphere: changes and their impacts. In: Watson RT, Zinyowera MC, Moss RH, Dokken DJ (eds) Climate change 1995. Impacts, adaptation and mitigation of climate change: scientific and technical analyses. Cambridge University Press, Cambridge, pp 241–265

126 Fuchs M et al (2020) Rapid fluvio-thermal erosion of a yedoma permafrost cliff in the Lena River Delta. Front Earth Sci 8. https://doi. org/10.3389/feart.2020.00336 Furian W, Loibl D, Schneider C (2021) Future glacial lakes in High Mountain Asia: an inventory and assessment of hazard potential from surrounding slopes. J Glaciol 67:653–670 Gardelle J, Berthier E, Arnaud Y (2012) Slight mass gain of Karakoram glaciers in the early twenty-first century. Nat Geosci 5(5):322–325 Gregory JM, George SE, Smith RS (2020) Large and irreversible future decline of the Greenland ice sheet. Cryosphere 14(12):4299–4322 Hogg AE, Gudmundsson GH (2017) Impacts of the Larsen-C Ice shelf calving event. Nat Clim Change 7(8):540–542 Holloway JE, Lewkowicz AG, Douglas TA, Li X, Turetsky MR, Baltzer JL, Jin H (2020) Impact of wildfire on permafrost landscapes: a review of recent advances and future prospects. Permaf Periglac Proc 31(3):371–382 ICIMOD (2023) Water, ice, society, and ecosystems in the Hindu Kush Himalaya: an outlook. https://doi.org/10.53055/ ICIMOD.1028. Accessed 21 June 2023 IMBIE Team (2020) Mass balance of the Greenland Ice Sheet from 1992 to 2018. Nature 579:233–239 Ingels J et al (2021) Antarctic ecosystem responses following ice‐shelf collapse and iceberg calving: science review and future research. Wiley Interdisc Rev: Clim Change 12(1):e682 Jackson RH et al (2020) Meltwater intrusions reveal mechanisms for rapid submarine melt at a tidewater glacier. Geophy Res Lett 47(2):e2019GL085335 Jin H, Li S, Cheng G, Shaoling W, Li X (2000) Permafrost and climatic change in China. Glob Planet Change 26(4):387–404 Johannessen OM, Shalina EV (2023) Will the summer sea ice in the Arctic reach a tipping point? Atmos Ocean Sci Lett 16(3):100352 Jones BM, Grosse G, Arp CD, Jones MC, Walter Anthony KM, Romanovsky VE (2011) Modern thermokarst lake dynamics in the continuous permafrost zone, northern Seward Peninsula, Alaska. J Geophys Res: Biogeosciences 116(G2). https://doi. org/10.1029/2011JG001666 Jorgenson MT et al (2022) Rapid transformation of tundra ecosystems from ice-wedge degradation. Glob Planet Change 216:103921 Kanevskiy M, Shur Y, Strauss J, Jorgenson T, Fortier D, Stephani E, Vasiliev A (2015) Patterns and rates of riverbank erosion involving ice-rich permafrost (yedoma) in northern Alaska. Geomorphology 253:370–384 Kaser G (1999) A review of the modern fluctuations of tropical glaciers. Glob Planet Change 22:93–103 Kavan J, Tallentire GD, Demidionov M, Dudek J, Strzelecki MC (2022) Fifty years of tidewater Glacier surface elevation and retreat dynamics along the south-east coast of Spitsbergen (Svalbard Archipelago). Remote Sens 14(2). https://doi.org/10.3390/ rs14020354 Khan SA et al (2022) Extensive inland thinning and speed-up of Northeast Greenland Ice Stream. Nature 611:727–732 Khromova T, Nosenko G, Kutuzov S, Muraviev A, Chernova L (2014) Glacier area changes in Northern Eurasia. Environ Res Lett 9(1):015003 Kirpotin SN, Polishchuk Y, Bryksina N (2009) Abrupt changes of thermokarst lakes in Western Siberia: impacts of climatic warming on permafrost melting. Int J Environ Stud 66:423–431 Knight J (2023) The last glaciers in Africa and their environmental implications. J Af Earth Sci:104863 Kochtitzky W, Copland L (2022) Retreat of Northern Hemisphere marine‐terminating glaciers, 2000–2020. Geophys Res Lett 49(3):e2021GL096501 Komori J (2008) Recent expansions of glacial lakes in the Bhutan Himalayas. Quat Int 18:177–186

5  The Cryosphere Kwong YTJ, Tau TY (1994) Northward migration of permafrost along the Mackenzie Highway and climatic warming. Clim Change 26:399–419 Laute K, Beylich AA (2020) Recent glacier changes and formation of new proglacial lakes at the Jostedalsbreen ice cap in southwest Norway. In: Beylich AA (ed) Landscapes and landforms of Norway. Springer, Cham, pp 71–95 Lenzano MG, Rivera A, Durand M, Vacaflor P, Carbonetti M, Lannutti E, Gende M, Lenzano L (2023). Detection of crustal uplift deformation in response to glacier wastage in Southern Patagonia. Remote Sens 15(3). https://doi.org/10.3390/rs15030584 Lewkowicz AG, Way RG (2019) Extremes of summer climate trigger thousands of thermokarst landslides in a High Arctic environment. Nat Commun 10(1):1329 Li J, Xu X (2023) Glacier change and its response to climate change in western China. Land 12(3). https://doi.org/10.3390/ land12030623 Ling F, Zhang T (2003) Impact of the timing and duration of seasonal snow cover on the active layer and permafrost in the Alaskan Arctic. Permafr Periglac Proc 14:141–150 Luo J, Niu F, Lin Z, Liu M, Yin G, Gao Z (2022) Abrupt increase in thermokarst lakes on the central Tibetan Plateau over the last 50 years. Catena 217:106497 Mackintosh AN, Anderson BM, Lorrey AM, Renwick JA, Frei P, Dean SM (2017) Regional cooling caused recent New Zealand glacier advances in a period of global warming. Nat Commun 8(1):14202 McGuire B (2012) Waking the giant. Oxford University Press, Oxford, p 303 Milillo P, Rignot E, Rizzoli P, Scheuchl B, Mouginot J, Bueso-Bello J, Prats-Iraola P (2019) Heterogeneous retreat and ice melt of Thwaites Glacier, West Antarctica. Sci Adv 5(1):eaau3433 Milillo P et al (2022) Rapid glacier retreat rates observed in West Antarctica. Nat Geosci 15(1):48–53 Minora U et al (2013) 2001–2010 glacier changes in the Central Karakoram National Park: a contribution to evaluate the magnitude and rate of the “Karakoram anomaly”. Cryosphere Disc 7(3):2891–2941 Mölg N (2014) Hasty retreat of glaciers in northern Patagonia from 1985–2011. J Glaciol 60:1033–1043 Mölg N et al (2021) Inventory and evolution of glacial lakes since the Little Ice Age: lessons from the case of Switzerland. Earth Surf Proc Landf 46:2551–2564 Molg T, Georges C, Kaser G (2003) The contribution of increased incoming shortwave radiation to the retreat of the Rwenzori Glaciers, East Africa, during the 20th century. Int J Climatol 23:291–303 Motyka RJ, O’Neal S, Connor CL, Echelmeyer KA (2002) Twentieth century thinning of Mendenhall Glacier, Alaska, and its relationship to climate, lake calving and glacier run-off. Glob Planet Change 35:93–112 Mouginot J et al (2019) Forty-six years of Greenland Ice Sheet mass balance from 1972 to 2018. Proc Nat Acad Sci 116(19):9239–9244 Muhammad S, Tian L, Nüsser M (2019) No significant mass loss in the glaciers of Astore Basin (North-Western Himalaya), between 1999 and 2016. J Glaciol 65:270–278 Navarro Á, Úbeda J, Gómez J, Pellitero R (2023) 1975–2018: 43 years of glacial retreat in the Incachiriasca Glacier (Nevado Salcantay, Vilcabamba Range, Peru). In: De Lázaro Torres ML, De Miguel GR (eds) Sustainable development goals in Europe: a geographical approach. Springer International Publishing, Cham, pp 263–278 Nelson FE, Anisimov OA (1993) Permafrost zonation in Russia under anthropogenic climate change. Permafr Periglac Proc 4:137–148 Nesje A, Lie O, Dahl SO (2000) Is the North Atlantic Oscillation reflected in glacier mass balance records? J Quat Sci 15:587–601 Nesje A, Bakke J, Dahl SO, Lie O, Matthews JA (2008) Norwegian mountain glaciers in the past, present and future. Glob Planet Change 60:10–27

References Nicholas JR, Hinkel KM (1996) Concurrent permafrost aggradation and degradation induced by forest clearing, central Alaska, USA. Arc Alp Res 28(3):294–299 Nie Y et al (2021) Glacial change and hydrological implications in the Himalaya and Karakoram. Nature Rev Earth Environ 2(2):91–106 Norris J, Carvalho LM, Jones C, Cannon F (2019) Deciphering the contrasting climatic trends between the central Himalaya and Karakoram with 36 years of WRF simulations. Clim Dynam 52:159–180 Nurakynov S et al (2023) Accelerated glacier area loss in the Zhetysu (Dzhungar) Alatau Range (Tien Shan) for the Period of 1956– 2016. Remote Sensing 15(8):2133 Oerlemans J et al (1998) Modelling the response of glaciers to climate warming. Clim Dynam 14:267–274 Olthof I, Fraser RH, Schmitt C (2015) Landsat-based mapping of thermokarst lake dynamics on the Tuktoyaktuk coastal plain, Northwest Territories, Canada since 1985. Remote Sens Environ 168:194–204 Paul F (2020) A 60-year chronology of glacier surges in the central Karakoram from the analysis of satellite image time-series. Geomorphology 352:106993 Pereira SR, Marquardt C, Beriain E, Lambert F (2021) Permafrost evolution in a mountain catchment near Santiago de Chile. J S Am Earth Sci 109:103293 Pritchard HD, Vaughan DG (2007) Widespread acceleration of tidewater glaciers on the Antarctic Peninsula. J Geophys Res 112:F03S29. https://doi.org/10.1029/2006JF000597 Purdie H, Anderson B, Chinn T, Owens I, Mackintosh A, Lawson W (2014) Franz Josef and Fox glaciers, New Zealand: historic length records. Glob Planet Change 121:41–52 Purdie H, Bealing P, Gomez C, Anderson B, Marsh OJ (2021) Morphological changes to the terminus of a maritime glacier during advance and retreat phases: Fox Glacier/Te Moeka o Tuawe. New Zealand. Geogr Ann A 103(2):167–185 Qureshi MA, Yi C, Xu X, Li Y (2017) Glacier status during the period 1973–2014 in the Hunza Basin, Western Karakoram. Quat Int 444:125–136 Rignot E, Mouginot J, Scheuchl B, Van Den Broeke M, Van Wessem MJ, Morlighem M (2019) Four decades of Antarctic Ice Sheet mass balance from 1979–2017. Proc Nat Acad Sci 116(4):1095–1103 Rignot E et  al. (2021) Retreat of Humboldt Gletscher, North Greenland, driven by undercutting from a warmer ocean. Geophys Res Lett 48(6):e2020GL091342 Rinzin S, Zhang G, Sattar A, Wangchuk S, Allen SK, Dunning S, Peng M (2023) GLOF hazard, exposure, vulnerability, and risk assessment of potentially dangerous glacial Lakes in the Bhutan Himalaya. J Hydrology 619:129311 Sannel ABK, Kuhry P (2011) Warming‐induced destabilization of peat plateau/thermokarst lake complexes. J Geophys Res: Biogeoscienc es 116(G3):doi:https://doi.org/10.1029/2010JG001635 Sattar A, Haritashya UK, Kargel JS, Karki A (2022) Transition of a small Himalayan glacier lake outburst flood to a giant transborder flood and debris flow. Sci Rep 12(1):12421 Scherler D, Bookhagen B, Strecker MR (2011) Spatially variable response of Himalayan glaciers to climate change affected by debris cover. Nat Geosci 4(3):156–159 Schöner W, Auer I, Böhm R (2000) Climate variability and glacier reaction in the Austrian eastern Alps. Ann Glaciol 31:31–38 Selyuzhenok V, Krumpen T, Mahoney A, Janout M, Gerdes R (2015) Seasonal and interannual variability of fast ice extent in the southeastern Laptev Sea between 1999 and 2013. J Geophys Res: Oceans 120(12):7791–7806 Șerban RD, Jin H, Șerban M, Luo D (2021) Shrinking thermokarst lakes and ponds on the northeastern Qinghai-Tibet plateau over the past three decades. Permafr Periglac Proc 32(4):601–617

127 Shrestha RR, Bonsal BR, Bonnyman JM, Cannon AJ, Najafi MR (2021) Heterogeneous snowpack response and snow drought occurrence across river basins of northwestern North America under 1.0 C to 4.0 C global warming. Clim Change 164:1–21 Siirila-Woodburn ER et al (2021) A low-to-no snow future and its impacts on water resources in the western United States. Nat Rev Earth Environ 2(11):800–819 Smith B, Fricker HA, Gardner AS, Medley B, Nilsson J, Paolo FS, Holschuh N, Adusumilli S, Brunt K, Csatho B,Harbeck K (2020) Pervasive ice sheet mass loss reflects competing ocean and atmosphere processes. Science368:1239–1242 Steffen T, Huss M, Estermann R, Hodel E, Farinotti D (2022) Volume, evolution, and sedimentation of future glacier lakes in Switzerland over the 21st century. Earth Surf Dynam 10(4):723–741 Stuart-Smith RF, Roe GH, Li S, Allen MR (2021) Increased outburst flood hazard from Lake Palcacocha due to human-induced glacier retreat. Nat Geosci 14(2):85–90 Taylor C, Robinson TR, Dunning S, Rachel Carr J, Westoby M (2023) Glacial lake outburst floods threaten millions globally. Nat Commun 14(1):487 Thompson LG, Davis ME, Mosley-Thompson E, Porter SE, Corrales GV, Shuman CA, Tucker CJ (2021) The impacts of warming on rapidly retreating high-altitude, low-latitude glaciers and ice corederived climate records. Glob Planet Change 203:103538 Tielidze LG, Jomelli V, Nosenko GA (2022a) Analysis of regional changes in geodetic mass balance for all Caucasus glaciers over the past two decades. Atmosphere 13(2):256 Tielidze LG, Nosenko GA, Khromova TE, Paul F (2022b) Strong acceleration of glacier area loss in the Greater Caucasus between 2000 and 2020. Cryosphere 16(2):489–504 Urbański JA, Litwicka D (2022) The decline of Svalbard landfast sea ice extent as a result of climate change. Oceanologia 64(3):535–545 Van der Ween CJ (2002) Polar ice sheets and global sea-level: how well can we predict the future? Glob Planet Change 32:165–194 Veettil BK, Kamp U (2019) Global disappearance of tropical mountain glaciers: observations, causes, and challenges. Geosciences 9(5):196 Veh G, Korup O, Walz A (2020) Hazard from Himalayan glacier lake outburst floods. Proc Nat Acad Sci 117(2):907–912 Venteris ER (1999) Rapid tide water glacier retreat: a comparison between Columbia Glacier, Alaska and Patagonian calving glaciers. Glob Planet Change 22:131–138 Vieli A (2021) Retreat instability of tidewater glaciers and marine ice sheets. In: Shroder JF (ed) Snow and ice-related hazards, risks, and disasters. Elsevier, Amsterdam, pp 671–706 Vilímek V, Zapata ML, Klimeš J, Patzelt Z, Santillán N (2005) Influence of glacial retreat on natural hazards of the Palcacocha Lake area, Peru. Landslides 2:107–115 Wang X, Siegert F, Zhou AG, Franke J (2013) Glacier and glacial lake changes and their relationship in the context of climate change, Central Tibetan Plateau 1972–2010. Glob Planet Change 111:246–257 Wang P, Li Z, Luo S, Bai J, Huai B, Wang F, Wang W, Wang L (2015) Five decades of changes in the glaciers on the Friendship Peak in the Altai Mountains, China: changes in area and ice surface elevation. Cold Regions Sci Technol 116:24–31 Wang X, Huang Y, Liu T, Du W (2023) Impacts of climate change on glacial retreat during 1990–2021 in the Chinese Altay Mountains. CATENA 228:107156 Webb EE, Liljedahl AK (2023) Diminishing lake area across the northern permafrost zone. Nat Geosci 16:202–209 Williams PJ (1986) Pipelines and permafrost: science in a cold climate. McGill-Queen’s Press, Montreal, p 140 Williams PJ (1995) Permafrost and climate change: geotechnical implications. Phil Trans Roy Soc London A352:347–358

128 Williams TJ, Quinton WL, Baltzer JL (2013) Linear disturbances on discontinuous permafrost: implications for thaw-induced changes to land cover and drainage patterns. Environ Res Lett 8(2):025006 Woo M-K, Lewkowicz AG, Rouse WR (1992) Response of the Canadian permafrost environment to climate change. Phys Geogr 13:287–317 Wood M et  al (2021) Ocean forcing drives glacier retreat in Greenland. Sci Adv 7(1):eaba7282 Yao T, Pu J, Lu A, Wang Y, Yu W (2007) Recent glacial retreat and its impact on hydrological processes on the Tibetan Plateau, China, and surrounding regions. Arc Antarc Alp Res 39:642–650 Yokohata T et al (2020) Model improvement and future projection of permafrost processes in a global land surface model. Progr Earth Planet Sci 7:1–12

5  The Cryosphere Yoshikawa K, Hinzman LD (2003) Shrinking thermokarst ponds and groundwater dynamics in discontinuous permafrost near Council, Alaska. Permafr Periglac Proc 14:151–160 Zhang G et al (2023) Underestimated mass loss from lake-terminating glaciers in the greater Himalaya. Nat Geosci 3:1–6 Zheng G et al (2021) Increasing risk of glacial lake outburst floods from future Third Pole deglaciation. Nat Clim Change 11(5):411–417 Zhu D, Tian L, Wang J, Wang Y, Cui J (2014) Rapid glacier retreat in the Naimona’Nyi region, western Himalayas, between 2003 and 2013. J Appl Remote Sen 8:083508–108350

6

Coasts

Abstract

Humans have modified coastlines. Sometimes this has been deliberate, as with the construction of various coastal defence structures, but many changes have been non-deliberate, including accelerated coastal erosion and the degradation of specific coastal types, including reefs, marshes, and mangroves. Coast lines will be highly susceptible to climate changes and to associated sea level rises.

Keywords

Beaches · Coastal defence · Marshes · Reclamation · Reefs

6.1 Introduction: Coastal Modification As Syvitski et al. (2020, p. 7) have written: Coastal engineering has globally added thousands of km of groins, jetties, seawalls, breakwaters and harbors to control the movement of coastal sediment, leading either to coastal erosion or to siltation. Lacking the delivery of silt from the interior, along with the rise of coastal aquaculture and coastal megacities, river deltas are subsiding at rates of tens to hundreds of mm/y. Many coastlines now retreat at highly variable rates of tens to hundreds of m/y, except where substantial seawalls are emplaced, as in the Netherlands. The global extent of wetlands today is ~10 Mkm2. Best estimates suggest that 54–57% of the total area of natural wetlands has already been lost, with the rate of loss accelerating during the 20th and 21st centuries. In many tropical areas, natural and protective mangrove swamps have been replaced with shrimp and fish farms (see Sect. 2.3), further exposing coastlines to erosion.

Coastal zones are home to huge numbers of people, and they have had a major impact on coastal landforms and processes (Viles and Spencer 1995). Bird (1979) divided human impacts into those that were direct and those that were indirect. He reviewed the effects of seawalls,

breakwaters, dredging and dumping, sediment availability, and vegetation change. Likewise, Walker (1984) wrote about both indirect and unintentional modifications and with direct and intentional modifications. He concentrated on land reclamation from the sea and coastal stabilisation. Walker and Mossa (1986, p. 116) were especially intrigued by the coast of Japan: In few environments is this ability better exemplified than along the world’s shorelines and in few countries is it more in evidence than in Japan. Japan, with a highly varied and dynamic coast, now supports some 8000 km of dikes and seawalls, 4000 harbours, 10,000 groins and jetties, and 3000 detached breakwaters. More than one-fourth of its over 32,000 km long shoreline is now considered artificial and another one-eighth as only seminatural.

Walker (1988) discussed the role of artificial structures more generally, while Bird (1996) wrote a general review of beach management. A good Australian treatment of coastal management is that by Harvey and Caton (2003). Nordstrom (2000) reviewed the beaches and dunes of developed coasts. He remarked that they were eliminated, altered through use, reshaped, remobilised, stabilised, or created to suit human needs. Among the mechanisms he addressed were the construction of buildings, agricultural development, mining, trampling by pedestrians, off-road vehicle use, afforestation, grazing, waste disposal, ground subsidence, and military use.

6.2 Deliberately Created Landforms 6.2.1 Coastal Defence Structures, Groynes, Tsunami Walls, etc. Various structures have been constructed along the world’s shorelines, including those for aquaculture, resource extraction, and the like (Bugnot et al. 2021). Along many shorelines, ‘hard engineering’ structures have been put in place for

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 A. Goudie, Landscapes of the Anthropocene with Google Earth, https://doi.org/10.1007/978-3-031-45385-4_6

129

130

coastal protection, and ‘shoreline hardening’ has taken place (Gittman et al. 2016). These structures include groynes of various morphologies (Fig. 6.1), seawalls, revetments, and the like (Reeve et al. 2011; Nordstrom 2014; Williams et al.

6 Coasts

2016). Along shorelines subject to tsunamis, tsunami walls have been constructed (Fig. 6.2) (Oetjen et al. 2022). As shown in Sect. 6.3.1, however, coastal defence structures can in some cases exacerbate problems of erosion.

Fig. 6.1  Coastal defence structures. Top: Google Earth image of defence structures on the Mediterranean coast of Israel in Tel Aviv. Scale bar is 700 m. Location: 32° 4′ 39.81ʺ N, 34° 46′ 2.59ʺ E. Bottom: Fishtail groynes causing beach accretion at Jaywick, Essex, England. Scale bar is 600 m. Location: 51° 46′ 33.29ʺ N, 1° 7′ 42.49ʺ E

6.2  Deliberately Created Landforms

131

Fig. 6.2  Tsunami defence walls. Top: Google Earth image of tsunami defence wall in Japan. Scale bar is 100 m. Location: 38° 59′ 47.64ʺ N, 141° 40′ 58.80ʺ E. Bottom: Google Earth image of tsunami defence walls at Kesennuma, Japan. Scale bar is 400 m. Location: 38° 49′ 30.77ʺ N, 141° 35′ 22.31ʺ E

For this reason, various ‘soft’ approaches to coastal defence have been developed, including beach nourishment, managed realignment, and the promotion of sedimentation in

mudflat environments (French 2001). Managed realignment is the organised abandonment of the former shoreline carried out with the intention of creating a more sustainable

132

future coast. In the UK it was put into practice in 1990 on Northey Island, Essex. In 2020 there were 52 realignment sites on the British coast, occupying 2690 ha (Oliver 2023).

6.2.2 Artificial Islands One type of coastal reclamation is the making of artificial islands. This has greatly developed in recent decades because of the availability of increasingly powerful means to dredge, drain, and dump sediment. The world’s largest artificial island is probably the Flevopolder in the Netherlands, which has an area of 970 km2 and was competed in 1968. Even more extraordinary is the construction of a series of islands on the shores of the Persian/Arabian Gulf: The Pearl-Qatar lies off Doha and has created over 32 km of new shoreline. The new Doha International Airport involved producing an island of some 20 km2 Bahrain has constructed the Durrat Al Bahrain with an area of 20 km2 off its southeastern shore and the Amwaj Islands with an area of 4.3 km2 off its northeastern shore Dubai has built (i) the Palm Jumeirah, which adds 78 km of extra shoreline, (ii) the Palm Jebel Ali, and (iii) The World, an artificial archipelago of c 300 islands in the rough shape of a world map. It adds roughly 232 km of extra shoreline (Fig. 6.3) In Ras Al Khaimah Emirate, the Al Marjan scheme has created a group of four islands offshore and has an area of c 2.7 km2

Inevitably, there are environmental implications of these schemes: they have involved the dredging of vast quantities of sediment from the sea floor, the construction of breakwaters which require massive quarrying of rock onshore, the obliteration of mangrove swamps, the degradation of corals (Rutz 2012), and the alteration of wave climates and sediment budgets. In some parts of the world, notably Hong Kong and Osaka (Japan), artificial islands have been built to accommodate new airports, while in the South China Sea, China is constructing artificial islands for strategic reasons (see Sect. 6.3.4). New islands may also be developed as part of tourist infrastructure, and this is the case in the Maldives (Fig. 6.4). In future, some island states may attempt to build artificial islands to overcome the effects of rising sea levels, as in Kiribati (Lister and Muk-Pavic 2015) or the Maldives (Brown et al. 2020).

6.2.3 Artificial Reefs Artificial reefs are submerged constructional structures placed on the seabed deliberately to mimic some characteristics of a natural reef (Ramm et al. 2021; Vivier et al.

6 Coasts

2021). They can be constructed from such materials as sunken ships and barges, old cars and tyres, dumped rock and concrete blocks, waste mussel and oyster shells, sandfilled geotextile cages, train carriages, pulverised fuel ash, rope netting, and abandoned oil rigs. They are created (i) to provide a habitat for fishes and thus to help artisanal fisheries, (ii) to give coastal protection and foreshore stabilisation, (iii) to restrict damage to sea grasses by trawlers, (iv) to act as a substratum upon which corals can grow and be rehabilitated (Perkol-Finkel et al. 2006), (v) to provide locations for recreational divers, (vi) to create improved conditions for surfers and body boarders, (vii) and for wind farms (Degraer et al. 2020). Their use has developed since the 1960s, and reviews of European examples are provided by Jensen (2002) and Fabi et al. (2011). Artificial surfing reefs are becoming more common in the UK (Rendle and Rodwell 2014), Portugal (Mendonça et al. 2011), and elsewhere, including Australia, and experiments are being undertaken to ascertain what the best shape is for the generation of optimal waves (e.g. Black and Mead 2009). To date their performance has been less than stellar.

6.2.4 Salt Pans For centuries humans have won salt from coastal environments. In Britain, for example, there are many mounds and embankments associated with coastal salt-making industries, some of which date back to the Neolithic (Sherlock 2021) (https://historicengland.org.uk/images-books/publications/iha-preindustrial-salterns/heag225-pre-industrialsalterns/) (accessed 25 March 2023). These ‘salterns’ were on a small scale, but today some salt pan areas are enormous and salt is won on an industrial scale, as in the Rann of Kutch, India (Fig. 6.5). Coastal salt making also has a long history in China (Chiang 1976), though in some areas the extent of salt pans has decreased as the land is converted to more profitable uses (Wang et al. 2015a, b). It is also widespread around the Mediterranean Sea, as in Tunisia (Fig. 6.6).

6.2.5 Coastal Reclamation Deliberate coastal reclamation to produce more available productive land has a long history, and in England the Romans, for example, started the reclamation of the Fens, Romney Marsh, and the Somerset Levels. The extent of reclamation of the Fens from Saxon times to the present has been described by Doody and Barnett (1987). Likewise, in Italy, the Pontine Marshes were drained in classical Roman times (Sevink et al. 2023). Many schemes were also developed in Europe in medieval times (Charlier et al. 2005).

6.2  Deliberately Created Landforms

133

Fig. 6.3  Google Earth images of the artificial islands of Dubai in 2002 (top) and 2022 (bottom). Scale bar is 10 km. Location: 24° 59′ 41.66ʺ N, 55° 3′ 24.64ʺ E

Coastal mega-cities, such as Penang in Malaysia (Chee et al. 2017), Hong Kong, Macau, Singapore, and Abu Dhabi have now expanded by reclaiming land from the sea. In the case of Singapore reclamation now amounts to

about 20% of its total area (Wang et al. 2015a, b) and has been at the expense of coral reefs and other landform types (Lai et al. 2015). Murray et al. (2014) mapped coastal reclamation around the Yellow Sea, between China and Korea,

134

6 Coasts

Fig. 6.4  Google Earth image of development of tourism structures in the Maldive Islands. Scale bar is 200 m. Location: 4° 15′ 39.90ʺ N, 73° 22′ 40.45ʺ E

and their analysis revealed that over a quarter of tidal flats existing in the 1980s had disappeared by the late 2000s (i.e. 1.2% annually). For China as a whole, there has been a reduction of coastal wetland area by slightly over 50% (Wang et al. 2014). The area par excellence of coastal reclamation is the Netherlands (Fig. 6.7) (Hoeksema 2007). The outline of the country in 1300, prior to major reclamation activity, is very different from what we see today. By the thirteenth century, the Dutch were regularly using windmills to pump water off reclaimed areas known as polders. About onequarter of the present total land area of the Netherlands has been reclaimed from the sea and from lakes during the past 800 years, the greatest achievement being the conversion of the former Zuiderzee into a freshwater lake, the Ijsselmeer, and the reclamation from it of four major polders together occupying 165,000  ha. In 1969, the Flevopolder was finished, as part of these. It has a total land surface of 970 km2, which makes it by far the largest artificial island created by land reclamation in the world. The island consists of two  polders, Eastern Flevoland and Southern Flevoland. This was achieved because between 1927 and 1932, a 30.5 km dyke (the Afsluitdijk) was constructed. There have also been major changes in the south of the country, involving the construction of dykes in the estuary/ delta of the Rhine–Meuse–Scheldt rivers.

Sengupta et al. (2023, p. 1) have summarised the global situation with regard to coastal reclamation, thus, based on their analysis of Landsat imagery from 2000 to 2020 for 135 cities with populations in excess of 1 million. Findings indicate that 78% (106/135) of these major coastal cities have resorted to reclamation as a source of new ground, contributing a total 253,000 ha of additional land to the Earth’s surface in the 21st century, equivalent to an area the size of Luxembourg. Reclamation is especially prominent in East Asia, the Middle East, and Southeast Asia, followed by Western Europe and West Africa. The most common land uses on reclaimed spaces are port extension (>70 cities), followed by residential/commercial (30 cities) and industrial (19 cities).

One can add to this that smaller coastal cities (such as Manama in Bahrain) have also undertaken extensive reclamation (Fig. 6.8).

6.3 Non-deliberate Changes 6.3.1 Accelerated Coastal Erosion Active erosion is a pervasive feature of many beaches, not least in the USA, where over two-thirds of the coastline of New England and the mid-Atlantic region of the USA has suffered from erosion in recent decades (Hapke et al. 2013). While most areas are subject to some degree of natural

6.3  Non-deliberate Changes

135

Fig. 6.5  Google Earth images of the construction of large salt pans in the twenty-first century in the Rann of Kutch, northern India. Scale bar is 10 km. Location: 23° 50′ 50.86ʺ N, 69° 17′ 48.24ʺ E

erosion and accretion, the balance can be upset by human activity. Paradoxically, some erosion has been accelerated as a result of efforts to reduce it. Seawalls, for example, can be a barrier which interrupts exchange and supply

of sediment between the beach and its hinterland (Hanley et al. 2014). A common cause of beach and cliff erosion at one point is coast protection at another. Beach formation is often encouraged by the construction of a range of ‘hard

136

6 Coasts

Fig. 6.6  Google Earth image of salt pans in Sfax, Tunisia. Scale bar is 1 km. Location: 34° 42′ 49.24ʺ N, 10° 44′ 59.29ʺ E

engineering’ structures. However, these sometimes merely displace the erosion (possibly in an even more marked form) further along the coast. This is illustrated in Fig. 6.9. Piers or breakwaters can have similar effects to groynes (Fig. 6.10). In recent years that is there has been an increasing trend towards so-called soft engineering as a means of coastal protection (Temmerman et al. 2013), rather than using ‘hard engineering’. It has always been said that a good beach is one of the best forms of coastal protection. If material is removed from a beach, accelerated cliff retreat may take place. Removal of beach materials may be necessary to secure valuable minerals, including heavy minerals or to provide aggregates for construction. Problems of coastal erosion are exacerbated because there is now abundant evidence to suggest that much of the reservoir of sand and shingle that creates beaches is in some respects a relict feature. It was transported shoreward and incorporated in present-day beaches during the phase of rapidly rising post-glacial sea levels that characterised the Flandrian (Holocene) transgression until about 6000 years BP. Since then, world sea levels have been much more stable, and much less material is, as a consequence, being added to beaches and shingle complexes. It is because of these problems that many erosion prevention schemes now involve beach nourishment (by the artificial addition of appropriate sediments to build up the beach) (Hanley et al. 2014) or employ miscellaneous sand bypassing techniques (including pumping and dredging)

whereby sediments are transferred from the accumulation side of an artificial barrier to the erosional side. In some areas, however, rivers bring material into the coastal zone which becomes incorporated into beaches through the mechanism of longshore drift. Thus any change in the sediment load of such rivers may result in a change in the sediment budget of neighbouring beaches. Where the sediment load is reduced through the construction of large reservoirs, behind which sediments accumulate, coastal erosion may result (Yang et al. 2011). In Texas, where over the last century four times as much coastal land has been lost as has been gained, one of the main reasons for this change is believed to be the reduction in the suspended loads of some of the rivers discharging into the Gulf of Mexico. These rivers carried in 1961–70 on average only about one-fifth of what they carried in 1931–40. Construction of great levées on the lower Mississippi River since 1717 (see Sect. 4.5) has also affected the Gulf of Mexico coast. The channelisation of the river has increased its velocity, reduced overbank deposition of silt onto swamps, marshes, and estuaries, and changed the salinity conditions of marshland plants. As a result, the coastal marshes and islands have suffered from increased erosion or a reduced rate of development. Likewise, in France the Rhône only carries about 5% of the load it did in the nineteenth century; and in Asia, the Indus discharges less than 20% of the load it did before construction of large barrages over the last half century (Milliman 1990). The sediment load of the Mekong has

6.3  Non-deliberate Changes

137

Fig. 6.7  Land reclamation in the Netherlands. Top: the Netherlands in 1300 and in the twentieth century. Middle: the progress of land reclamation in the Netherlands since 1300. Modified by author from various sources

138

6 Coasts

Fig. 6.8  Google Earth images of land reclamation in Manama, Bahrain, between 2002 (top) and 2022 (bottom). Scale bar is 5 km. Location: 26° 13′ 27.20ʺ N, 50° 32′ 22.13ʺ E

been reduced by c 74% over pre-dam levels (Van Binh et al. 2020). The total annual sediment load of major Chinese rivers transported to the coast decreased from 2.03 billion t per year during the period 1955–1968 to 0.50 billion t per

year during the period 1997–2010, largely as a result of dam construction (Liu et al. 2021). For example, the annual sediment load of the Yangtze decreased from 488.75 × 106 t per year in the late 1950s to 128.35 × 106 t per year in the

6.3  Non-deliberate Changes

139

Fig. 6.9  Google Earth image of the interruption of longshore drift by groynes on Cape Cod, USA. Scale bar is 100 m. Location: 41° 39′ 5.52ʺ N, 70° 8′ 58.96ʺ W

2010s (Tian et al. 2021). On a global basis, large dams may retain 25–30% of the global flux of river sediment (Vörösmarty et al. 2003) (see also Sect. 4.2). Anthony (2015) argued that the current tendency for there to be significant reductions in fluvial sediment supply to deltas may signify the demise of many of them in the coming decades through a process of delta shoreline straitening by waves. In some areas anthropogenic vegetation modification creates increased erosion potential. On the hurricaneafflicted coast of Belize, Central America, Stoddart (1971) showed that natural, dense vegetation thickets on low, sand islands (cays) acted as a baffle against waves and served as a massive sediment trap for coral blocks, shingle, and sand transported during extreme storms. When, however, the natural vegetation was replaced by coconut plantations, the hurricane threat increased because these had an open structure easily penetrated by sea water, tended to have little or no ground vegetation (thus exposing the cay surface to stripping and channelling), and had a dense but shallow root net easily undermined by wave attack.

6.3.2 Changing Salt Marshes Salt marshes are important habitats for wildlife and also help in coastal protection. There are many ways in which they have been transformed by humans, including by

drainage (Fig. 6.11). In some parts of the world they have shown high rates of loss. In South Africa, for example, approximately 43% of salt marsh habitat has been lost due to encroaching development and agriculture from the 1930s to 2018 (Adams 2020). In China, the area of salt marshes has declined considerably from 151,324 ha in 1985 to 115,397 ha in 2019, a drop of 23.7% (Chen et al. 2022). Globally, McOwen et al. (2017) estimated the loss of salt marsh at between 25 and 50%. In many parts of the world, the nature of some salt marshes, and the rate at which they accrete, has been transformed by major vegetational changes. One of the most spectacular cases of this is illustrated by the hexaploid Spartina alterniflora, native to the North American Atlantic coast, and its repeated introductions over the last two centuries, southwards (e.g. Brazil, Argentina; South Africa), westwards to the Pacific coast of California, eastwards to the west European Atlantic coasts, including the Wadden Sea, and to China, where populations have spectacularly expanded in the last decade. In Europe, hybridisation between S. alterniflora and the native S. maritima resulted in the formation of a vigorous and successful allododecaploid species, Spartina anglica, which rapidly expanded on European saltmarshes and is now introduced in several continents (Ainouche and Gray 2016). It spread rapidly in Britain (Doody 1984). The plant has often been effective at excluding other species and also at trapping sediment.

140

6 Coasts

Fig. 6.10  Erosion and accretion. Top: Google Earth image of beach erosion and accretion associated with the harbour wall at Rye, southern England. Scale bar is 500 m. Location: 50° 55′ 51.98ʺ N, 0° 46′ 25.40ʺ E. Bottom: Google Earth image of beach accretion on one side of a breakwater and sediment depletion on the other at Long Beach, California. Scale bar is 600 m. Location: 33° 44′ 55.09ʺ N, 118° 6′ 22.99ʺ W

Rates of accretion can therefore become very high. This caused progressive silting up of estuaries such as those of the Dee. In the Yangtze estuary of China it has had a great

competitive effect on native species, including Scirpus mariqueter and Phragmites australis, and the conversion of mudflats to Spartina meadows has taken place (Li et al.

6.3  Non-deliberate Changes

141

Fig. 6.11  Google Earth images of salt marshes in Essex, south eastern England. The top image (scale bar is 90 m) shows a more or less natural marsh, whereas the bottom image (scale bar is 100 m) shows a marsh with linear drainage features. Locations: 51° 52′ 48.34ʺ N, 1° 13′ 46.81ʺ E (top), 51° 53′ 18.34ʺ N, 1° 14′ 10.78ʺ E (bottom)

2009). On the positive side, the presence of Spartina meadows dampens down wave erosion and can contribute to coastal defence (Zhang et al. 2023).

However, Spartina invasion is only one of the causes of changes in accretion rates on marshes (Gedan et al. 2011). Other important factors include changed water and sediment

142

inputs from the land as a result of land cover changes (Mattheus et al. 2010; Ladd et al. 2019), the construction of dykes and levees, the digging of canals, the throwing up of spoil banks, land reclamation schemes, drainage ditches, tidal restriction by bridges and berms, and subsidence resulting from fluid abstraction (Gedan et al. 2009). In some parts of the world, including eastern England, northwest Europe, Canada, and the USA, marsh growth is now being actively encouraged by the removal of coastal defence structures, such as seawalls, and the allowing of natural sediment to accumulate to construct a new marsh on what was agricultural land. The intention is to mitigate flood and erosion risks, act as a buffer against storm surges, and to create more natural shorelines. It is also a means of coping with what has been described as ‘coastal squeeze’— the problem of marsh development in the face of sea level rise when inward migration is stopped by the presence of seawalls (Leo et al. 2019; Silva et al. 2020). This ‘managed realignment’ has been described by Esteves (2014) and Friess et al. (2014). As Boorman and Hazelden (2017, p. 389) explained, this is defined as: …..the adoption of a new, generally landwards situated, sea defence line, usually a sea wall but which may be on rising ground or upland. Where a sea defence line is in the form of a sea wall, and is to be relocated landwards, then there are two options for the old sea wall. Most commonly the wall is breached giving the sea access through one or more openings in the wall; but a more expensive option is to remove the old wall completely. Either way, this increases the inter-tidal area and facilitates new inter-tidal habitat development, most desirably salt marsh, seaward of this wall as an ecological buffer. Using salt marsh vegetation as a buffer affords the sea wall additional protection from erosion and thus saves on building and maintenance costs.

One method of protecting low coastlines is to encourage sedimentation on mud flats, using such means as brushwood fencing (see French 2001, pp. 246–251).

6.3.3 Mangroves Mangroves are coastal intertidal wetland forests composed of halophytic trees and shrubs. In 2020 there was an estimated 147,359 km2 of mangrove forest globally, 51% of which occurred in the Asia–Pacific, 29% in the Americas, and 20% in Africa. Indonesia had the largest area of mangrove forest—totalling 20% of the global total—followed by Brazil, Australia, Mexico, and Nigeria, which together contain almost half of the world’s mangroves (UNEP 2023). Even though they cover just 0.1% of the Earth’s continental surface, they are nonetheless of extreme importance, not least because they and their associated soils and sediments are hugely important stores of carbon (Atwood et al. 2017; Richards et al. 2020). In addition,

6 Coasts

these ecosystems constitute a reservoir, refuge, feeding ground, and nursery for many useful and unusual plants and animals. Moreover, they can serve as buffers against the erosion caused by tropical storms—a crucial consideration in low-lying areas like Bangladesh. In spite of these obvious advantages, mangrove forests are being degraded and destroyed on a large scale in many parts of the world, either through exploitation of their wood resources or because of their conversion to agriculture, aquaculture, salt-evaporation ponds, and infrastructure or urban developments (Fig. 6.12). This has been the case with the Sunderbans, where the cover of dense mangrove forest declined at an annual average rate of 1.3% from 1975 to 2020 (Akbar Hossain et al. 2022). Aquaculture has traditionally been seen as a leading cause of mangrove deforestation and fragmentation. Onshore aquaculture for fish and shellfish production was the leading cause of mangrove deforestation during the second half of the twentieth century (Friess et al. 2019), and globally it is responsible for just over half of mangrove declines. More recently, the expansion of oil palm plantations (see Sect. 2.5) has accounted for 16% of their loss in Southeast Asia between 2000 and 2012 (Friess 2016). FAO data suggests that the world’s mangrove forests, which covered 19.8 Mha in 1980, have now been reduced to just 14.7 Mha. The annual loss is running at about 1% per year (compared to 1.7% a year from 1980 to 1990) (http://www.fao. org/DOCREP/005/Y7581E/y7581e04.htm) (accessed 15 July 2017). Friess (2016) and Friess et al. (2019) reported that deforestation rates in some parts of the world have decreased over the last decade, possibly because easily transformed sites have now been exploited, or because of an increasing appreciation of the value that mangrove swamps have. For example, while in the 1970s–1990s it was assumed that mangroves in Southeast Asia were being lost at an annual rate of c 1% per year, recent analyses suggest that this has decreased to c 0.2%. Bhowmik et al. (2022) reported an overall decline (net loss) of more than 5% in global coverage between 1990 and 2020. Globally, the mangrove cover declined by 8600 km2 between 1990 and 2020. The south and southeast Asian region experienced the highest mangrove loss (3870 km2 and more than 6% decline in the global coverage) between 1990 and 2020. Among the Asian countries, Indonesia encountered the highest areal loss (more than 700 km2), while Malaysia experienced the highest loss in percentage (more than 3%) between 2000 and 2010. The situation in Myanmar has been described as ‘catastrophic’ (De Alban et al. 2020). For the 1996–2016 period net national mangrove cover declined by 52%, with annual net loss rates of 3.6–3.9%. Lacerda et al. (2022) suggested that between 1996 and 2016 global annual mangrove loss was about 0.21% of the total area, whereas in north

6.3  Non-deliberate Changes

143

Fig. 6.12  Google Earth image of the Sunderbans of India and Bangladesh. The darker areas are mangrove swamps, while the lighter areas are those that have been cleared. Scale bar is 50 km. Location: 22° 1′ 55.35ʺ N, 89° 17′ 50.58ʺ E

and central America and the Caribbean the average rate was 0.36% and in southeast Asia 0.29%. They reported that other regions showed lower rates, such as the Middle East (0.23%) and Australasia and South America (0.14%). Even lower loss rates occurred in west and central Africa and the Pacific Islands (0.06%), and there was even a small gain in mangrove area of 0.03% year−1 in the east Asia.

6.3.4 Coral Reefs Coral reefs are important because they are among the most diverse, productive, and beautiful communities in the world. They provide many ecological services (Woodhead et al. 2019). In addition, they also provide coastal protection, opportunities for recreation and tourism, potential sources of substances like drugs, and livelihoods for fishermen. They have been called the marine version of the tropical rainforests, rivalling their terrestrial counterparts in both richness of species and biological productivity. As HoeghGuldberg et al. (2019, p. 2) have pointed out, ‘Many human coastal communities, comprised of at least 500 million people worldwide, have developed a high degree of dependency on ecosystem goods and services provided by coral reefs’. Coral reefs are undergoing profound change at the present time. Many are being heavily degraded. The Great Barrier Reef has suffered from a group of recent pressures:

predation by the crown-of-thorns starfish, bleaching events associated with elevated temperatures, and pollution by sediment. As Pandolfi et al. (2005, p. 1275) remarked, ‘Large animals, like turtles, sharks and groupers, were once abundant on all coral reefs, and large long-lived corals created a complex architecture supporting diverse fish and invertebrates. Today the most degraded reefs are little more than rubble, seaweed, and slime’. Severe declines in coral cover on reefs have been identified in recent decades, though there are debates as to just how serious the degradation has been, not least in the context of the Great Barrier Reef (GBR) of Australia (Hughes et al. 2011; Sweatman et al. 2011). In the Indo-Pacific region coral cover declined from 42.5% in the early 1980s to only 22.1% by 2003, an average annual loss rate of 1%. In the Caribbean between 1977 and 2001 the annual rate was even higher—1.5% (Bruno and Selig 2007), and over the last 25–30 years coral cover in that region has fallen from an average of roughly 50% to only 10% (Hughes et al. 2013). Reductions in the cover of hard corals are often associated with an increase in algal communities, especially in the coral zones of the Western Atlantic (Tebbett et al. 2023). Accelerated sedimentation resulting from poor land management (Fabricius 2005), together with dredging, is probably responsible for more damage to reef communities than any other mechanism, for suspended sediments create

144

turbidity which restricts the light penetration which is necessary for coral growth (López-Londoño et al. 2021). Also, the soft, shifting sediments may not favour colonisation by reef organisms. An interesting example of increased rates of sedimentation is provided by geochemical studies of longlived corals from Australia’s Great Barrier Reef (McCulloch et al. 2003). These showed that since 1870 and the start of European settlement in its catchment, the Burdekin River has carried five to ten times more sediment to the reef than it did previously. Recently, there has been some amelioration of the problem as the construction of the Burdekin Falls Dam (completed in 1987) has reduced sediment loadings (Lewis et al. 2021). Pollution is an increasingly serious problem, particularly in areas with a dense human population (Tkachenko 2017). Sewage is the second worst form of stress to which coral reefs are exposed, for oxygen-consuming substances in sewage result in reduced levels of oxygen in the water of lagoons. Sewage may also cause nutrient enrichment to stimulate algal growth and feed various predators, which in turn can overwhelm coral. Some of the sewage is caused by the growth of tourism (Lachs et al. 2019). Runoff from the land can also cause nutrient enrichment, because it may contain nitrates and other nutrients derived from fertilisers. Equally, poor land management can also cause salinity levels to be reduced below the level of tolerance of reef communities because of accelerated runoff of freshwater from catchments draining into lagoons. The vast increase in the number of cruise ships can also produce a great deal of pollution and waste (Lloret et al. 2021). Reefs may also be threatened by coral bleaching associated with recent global heating. Coral bleaching is a result of the breakdown of the symbiosis between corals and their symbiotic microalgae, causing the loss of pigments and symbionts, giving corals a pale, bleached appearance. It can be fatal (Sully et al. 2019; Van Woesik et al. 2022). UNEP (https://www.unep.org/interactives/status-world-coralreefs/) (accessed 8 June 2023) has reported: At the global scale, the estimated average cover of living hard coral exhibited distinct fluctuations during the last 40 years. Prior to the first mass coral bleaching event in 1998, the global average cover of hard coral was high (>30%) and stable, although the scarcity of data prior to 1998 reduced the level of certainty in estimates. The 1998 coral bleaching event killed approximately 8% of the world’s coral. To put this into context, this represents more than the total amount of living coral in any one of the Caribbean, Red Sea and Gulf of Aden, South Asia or Western Indian Ocean regions. During the subsequent decade, the global average cover of hard coral recovered to pre1998 levels (33.3% in 2009), but between 2009 and 2018, there was a progressive loss amounting to 14% of the coral from the world’s coral reefs, which is more than all the coral currently living on Australia’s coral reefs.

6 Coasts

In the longer term, reefs may also be adversely affected by ocean acidification associated with increasing carbon dioxide levels in ocean waters (Davis et al. 2021). This is an issue that will be returned to in Sect. 6.4.3. Increased warming and other processes have led to the loss of dissolved oxygen in the oceans. This hypoxia is likely to increase in a warmer and could have negative consequences for coral reef taxa due to the key role of oxygen in organism functioning and fitness (Pezner et al. 2023). Many areas are showing increasing production of what is called ‘coral rubble’ (Kenyon et al 2023). This is produced when various mechanical, biological, and/or chemical processes fracture live coral colonies or the reef framework, creating fragments and rubble. It is often observed following disturbances from extreme storm events, but bio-erosive processes also reduce the structural integrity of carbonate material, accelerating the likelihood of fragmentation and net reef erosion. In addition, rubble production and its extent are worsened as a result of increasing direct human disturbances, including ship groundings, damage from anchors, blast fishing, mining of coral, and trampling. As we have seen above, heatwaves can also cause coral bleaching and mortality, and altered coral assemblages, and are increasing in intensity and frequency as sea surface temperatures rise, with subsequent increases in the generation of rubble. This is significant because the unstable and unconsolidated nature of the rubble makes it susceptible to frequent mobilisation, and this shifting substrate can lead to low coral recruitment, as coral fragments, recruits, and juveniles are abraded and smothered, limiting reef regeneration and recovery. Some small islands have suffered from severe erosion. As Thomas et al. (2020, p. 6) reported, ‘Several low-lying Pacific Islands in the Solomon Islands and Micronesia have already been lost—including Kale and Rapita in the northern Solomon Islands—and more are experiencing severe erosion due to sea-level rise since the mid-twentieth century. Severe erosion on the islands of Hetaheta and Sogomou in the northern Solomon Islands has led to 62% and 55% island loss, respectively, over the twentieth century. On the island of Nuatambu, 51% land loss in the village area and subsequent 50% house loss directly attributable to shoreline recession has led to the forced relocation of communities’. In some parts of the world, coral islands are being transformed by the installation of air ports and various military facilities. This has been the case in the South China Sea where the surfaces of some islands are now totally covered (Figs. 6.13 and 6.14) (Barnes and Hu 2016). Extensive construction works have also been undertaken to provide tourist infrastructure, as in the Maldives (Duvat 2020; Holdaway et al. 2021) (see Sect. 6.2.2).

6.3  Non-deliberate Changes

145

Fig. 6.13  Google Earth images of Subi Reef, South China Sea, in 2004 (top) and 2021 (bottom). Scale bar is 2 km. Location: 10° 55′ 21.57ʺ N, 114° 5′ 11.95ʺ E

146

6 Coasts

Fig. 6.14  Google Earth image of Fiery Cross Reef in 2014 (top) and 2022 (bottom). Scale bar is 2 km. Location: 9° 32′ 56.09ʺ N, 112° 53′ 19.17ʺ E

6.4  The Future

For all these reasons, many attempts are being made to undertake restoration to halt or reverse reef degradation, but so far there has been limited success, especially at the large scale (Hughes et al. 2023).

6.3.5 Estuaries Estuaries have been transformed by various human activities, including accelerated sedimentation caused by accelerated soil erosion upstream and reduced sedimentation caused by dam construction (Ezcurra et al. 2019). Also very important have been the construction of jetties at their mouths, construction works such as training walls associated with navigation, embankments, dredging, and land reclamation (see, for example, Pasternack et al. 2001; Poirier et al. 2011; Irabien et al. 2015; Flor-Blanco et al. 2015; Pye and Blott 2014). There are also more and more storm surge barriers being constructed across estuaries, and these have major impacts on tidal scour, sedimentation, and marsh development (Orton et al. 2023). Let us consider two examples from the USA. First, Jalowska et al. (2015) reported on the history of the Roanoke bayhead delta in North Carolina. After the mid1600s AD, when the first European settlers began to clear forest for farming, the delta rapidly accreted and the interdistributary bay filled with sediment from increased agricultural runoff. Regression was also facilitated by the low rates of sea level rise at that time (− 0.01 to 0.047 cm per year compared to 0.37 cm per year today) (see Sect. 6.4.1). An episode of bayhead delta retreat was then initiated during the nineteenth century and this continues today. This is because improved agricultural practices and dam construction upstream have decreased the amount of sediment being delivered. The San Francisco Bay estuary in California is the largest estuary on the west coast of North America. It has lost over 90% of its tidal wetlands through conversion to agriculture, grazing, or urban development (Parker and Boyer 2019). Jaffe et al. (2007) surveyed the changing rates of sedimentation in part of this great estuary—San Pablo Bay. Their analysis of a series of historical bathymetric surveys revealed large changes in morphology and sedimentation. In 1856, the morphology of this bay was complex, with a broad main channel, a major side channel connecting to the Petaluma River, and an ebb-tidal delta crossing shallow parts of the bay. In 1983, its morphology was much simpler because all channels except the main one had filled with sediment and erosion had planed the shallows, creating a uniform gently sloping surface. These changes were influenced by human activities that altered sediment delivery from inflowing rivers. Thus from 1856 to

147

1887, high sediment delivery (14.1 × 106 m3 per year) during the hydraulic gold-mining period in the Sierra Nevada Mountains resulted in net deposition of 259 ± 14 × 106 m3 in San Pablo Bay. This rapid deposition filled channels and increased the intertidal mudflat area by 60%. However, from 1951 to 1983, 23  ± 3 × 106 m3 of sediment was eroded from San Pablo Bay as sediment delivery from the Sacramento and San Joaquin rivers decreased to a mere 2.8 × 106 m3 per year because of damming of rivers, riverbank protection, and altered land use. Intertidal mudflat area in 1983 was 31.8 ± 3.9  km2, similar to that in 1856. Figure 6.15 shows a heavily affected estuary in northwest Madagascar. Here, soil erosion has increased the sediment load of the Betsiboka, Madagascar’s largest river. Entrained lateritic sediments, derived from erosion in the interior, colour the river a blood-red hue. As a result, Bombetoka Bay has significantly changed during the past 30 years, with a dramatic increase in the amount of sediment moved by the river and deposited in the estuary and in offshore delta lobes (Raharimahafa and Kusky 2010).

6.4 The Future 6.4.1 The Amount of Sea Level Rise by 2100 In most areas, sea levels are rising and will continue to rise because of the steric (thermal) effect and the increasing rate of melting of glaciers and ice masses (Hamlington et al. 2020). The average rate of sea level rise (SLR) was 1.3 mm yr−1 between 1901 and 1971, increasing to 1.9 mm per year between 1971 and 2006 and further increasing to 3.7 mm per year between 2006 and 2018 (https://report. ipcc.ch/ar6syr/pdf/IPCC_AR6_SYR_LongerReport.pdf) (accessed 24 March 2023). The WMO (https://library.wmo. int/doc_num.php?explnum_id=11593) (accessed 8 June 2023) reported in 2023 that global annual SLR was estimated to be 3.4 ± 0.3 mm over the 30 years of the satellite altimeter record (1993–2022), but that the rate has doubled between the first decade of the record (1993–2002) and the last (2013–2022), during which the rate has exceeded 4 mm per year. The acceleration in global mean sea level was estimated to be 0.12 ± 0.05 mm per year over the 30-year period. Over the years there has been a considerable diversity of views about how much SLR is likely to occur by 2100. In general, however, estimates have tended to be revised downwards through time (Pirazzoli 1996), but with increasing evidence that polar ice sheets are melting rapidly (Rignot et al. 2011), rates should now perhaps be revised upwards. By the end of the century sea level might

148

6 Coasts

Fig. 6.15  Google Earth image of estuarine accelerated sedimentation in northwest Madagascar. Scale bar is 30 km. Location: 15° 56′ 17.94ʺ S, 46° 25′ 41.00ʺ

be 0.5–1.4 m above the 1990 level or even 0.75–1.9 m (Vermeer and Rahmstorf 2009). Nicholls et al. (2011) believed that with a 4 °C or more rise in temperature that a credible upper bound for twenty-first century SLR is 2 m. A recent IPCC report (2022) (https://www.ipcc.ch/report/ar6/ wg2/downloads/report/IPCC_AR6_WGII_Chapter03.pdf) (accessed 8 June 2023) predicts that global mean sea level will rise between 0.43 and 0.84 m by 2100 relative to 1986– 2005. The amount of SLR will show regional variations due to such factors as climate-forced circulation changes and gravitational effects resulting from glacier and land ice mass changes, and one area where SLR will be greater than the global norm is the heavily populated Atlantic coastline in the vicinity of New York, USA (Carson et al. 2016; Davis and Vinogradova 2017).

6.4.2 Land Subsidence The effects of global SLR will be compounded in those areas that suffer from local subsidence as a result of tectonic movements, isostatic adjustments, and fluid abstraction (see Sect. 8.2) (Nienhuis et al. 2023). Areas where land is rising because of isostasy (e.g. Fennoscandia or the Canadian Shield) or because of tectonic uplift (e.g. much of the Pacific coast of the Americas) will be less at risk

than regions that are subsiding. Loading of sediment onto the world’s great river deltas (e.g. India, Ganges, Mekong, Tigris-Euphrates and Zambezi) causes subsidence to occur, and in addition, sediment compaction occurs through time. Some areas subside because of on-going adjustment to the application and removal of ice loadings to the crust in the Pleistocene. During glacials, areas directly under the weight of ice caps were depressed, whereas areas adjacent to them bobbed up by way of compensation (the so-called peripheral bulge). Conversely, during the Holocene, following removal of the ice load, the formerly glaciated areas have rebounded whereas the marginal areas have foundered. A good example of this is the Atlantic coast of North America (Engelhart et al. 2009) or the southeast coast of England. Elsewhere, a range of human actions can promote subsidence (see Chap. 8): the withdrawal fluids; the extraction of solids through mining; the hydrocompaction of sediments; the oxidation and shrinkage of organic deposits (e.g. peat) peats; the degradation of permafrost; and the catastrophic development of sinkholes in karstic terrain. Even the shear weight of buildings in cities like New York may cause some subsidence (Parsons et al. 2023). In some areas of subsidence caused by humans the rate of subsidence can be over 20 mm per year, as in Bahrain. The highest subsidence rates appear in Tianjin (China), Semarang (Indonesia),

6.4  The Future

and Jakarta (Indonesia), where maximum rates exceed 30 mm per year—dwarfing global mean SLR by over ten times (Wu et al. 2022).

6.4.3 Reefs Coral reefs face a suite of threats from climate change, SLR, and ocean acidification (Kayanne 2016; Hughes et al. 2017; Hoegh-Guldberg et al. 2019). Those corals stressed by temperature or pollution might well find it more difficult to cope with rapidly rising sea levels than would healthy corals. One potential change is that of increasing hurricane frequency, intensity, and distribution. They might build some coral islands up, erase others, and through high levels of runoff and sediment delivery they could change the turbidity and salinity of the water in which corals grow. This is discussed further in Sect. 2.9. Increased sea surface temperature could have deleterious consequences for corals which are near their thermal maximum (Hoegh-Guldberg et al. 2019). Most coral species cannot tolerate temperatures greater than about 30 °C, and even a rise of 1–2 °C could adversely affect many shallow water species. As seen in Sect. 6.3.4 coral bleaching was a widespread feature in the warm years of the 1980s and 1990s. The mass coral bleaching, which occurred continuously across different parts of the tropics from 2014 to 2016, is considered the longest and most severe global coral bleaching event on record, and the Great Barrier Reef underwent mass bleaching three times between 2016 and 2020 (IPCC 2022, Chap. 3, p. 410). Hoegh-Guldberg (1999) and subsequent workers (e.g. McWhorter et al. 2022) have suggested that continued warming trends superimposed on interannual and decadal patterns of variability are likely to increase the incidence of bleaching and coral mortality unless significant adaptation to increased temperatures occurs. Teneva et al. (2012) suggested that the most threatened reefs may be in the Central and Western Equatorial Pacific. On the other hand, some corals appear to have an ability to acclimatise to elevated temperatures (Palumbi et al. 2014; Sweet and Brown 2016) allowing them to inhabit reef areas with water temperatures far above their expected tolerances. Such acclimatisation offers some hope for coral survival (Coles et al. 2018; De Carlo et al. 2019; Sully et al. 2019; Van Woesik et al. 2022), but it is an area where our understanding is still very limited (Torda et al. 2017). SLR is another crucial issue. In the 1980s there were widespread fears that if rates of SLR were high (perhaps 2–3 m or more by 2100) then coral reefs would be unable to keep up, so that submergence of atolls might occur. Particularly vulnerable were Tokelau, the Marshall Islands, Tuvalu, the Line Islands, Kiribati in the Pacific Ocean,

149

and the Maldives in the Indian Ocean. Reefs have a range of topographies, and low-lying reef islands on the rims of atolls may be especially vulnerable to the effects of SLR (Woodroffe 2008). However, with the reduced expectations for the degree of SLR that may occur (see Sect. 6.4.1), there has arisen a belief that coral reefs may survive and even prosper with moderate rates of SLR. During the early Late Pleistocene and early Holocene, rates of SLR were sometimes 30–50 mm yr−1, which is markedly higher than those generally predicted for coming decades. In spite of this coral reefs grew upwards at a modal rate of 6–7 mm yr−1. The implication of this is that it is unlikely that existing coral reefs will be extensively ‘drowned out’ by any likely future SLR (Kench et al. 2009). On the other hand, because of the effects of coral bleaching, and pollution, by sewage and sediment there is some evidence in the Caribbean that rates of coral accretion have declined in recent years (Perry et al. 2013). This makes it more difficult for reefs to keep up with SLR. Reefs may also suffer from increasing ocean acidification (Royal Society 2005), for a proportion of the extra carbon dioxide being released into the atmosphere by the burning of fossil fuels and biomass is absorbed by sea water. This produces carbonic acid, an increase of which will cause that water to become more acidic (i.e. it will have a lower pH than now). This will be particularly harmful to those organisms, including scleractinian corals, which are dependent on the presence of carbonate ions to build their hard parts out of calcium bicarbonate (Orr et al. 2005; Pelejero et al. 2010). However, there may also be a range of indirect effects of ocean acidification on corals, including changes in competition between different hard corals, soft corals winning more competitive interactions with hard corals, interactions with macroalgae, predation, bio-eroder abundance, and disease dynamics (Hill and Hoogenboom 2022). The absorption of carbon dioxide has already caused the pH of modern sea surface waters to be more acidic and less alkaline than they were in pre-industrial times. The IPCC (2022) reported that the pH of global surface waters has decreased from 8.2 to 8.1 since the pre-industrial era (1750 CE). Ocean pH may fall an additional 0.3 units by 2100 (Caldeira and Wickett 2003), which means that the oceans may be more acidic than they have been for 25 million years. Doney (2006) warned that several centuries from now, if we continue to add carbon dioxide to the atmosphere, ocean pH may be lower than at any time in the past 300 million years. Another reason why which coral reefs may change is that future wave environments may be transformed (Quataert et al. 2015). Future coral bleaching events and ocean acidification could kill off corals, reduce their cover, and result in a decrease in their hydrodynamic roughness. Together or independently, this will reduce bottom friction,

150

which in turn would increase wave heights, wave run-up, and wave-driven flooding. In addition, climate change may drive changes in extreme wave heights and their directions. Coral reefs play an important role in coastal protection against storms so that ‘we can anticipate that decreasing rates of reef accretion, increasing rates of bio-erosion, rising sea-levels, and intensifying storms may combine to jeopardize a wide range of coastal barriers’ (HoeghGuldberg et al. 2007, p. 1742). Overall, some predictions for the future health of reefs are exceedingly pessimistic. For instance, Sale wrote (2013, p. 325): Coral reefs, as we knew them in the 1970s, are likely to have disappeared entirely from the planet by 2050, if current trends in human environmental impacts continue….What will be left is eroding limestone benches, dominated by macroalgae, and with small isolated coral colonies.

Equally, Spalding and Brown (2015, p. 771) have warned: Without the stabilization of greenhouse gas concentrations, it seems inevitable that many of the world’s coral reefs will become nonaccreting habitats—they will, based on most common definitions, cease to be coral reefs. This will happen more or less rapidly in different locations and will have concomitant and profound impacts on both biodiversity and people. As reefs decline, many of the millions of people who live near reefs will lose critical sources of food, as well as coastal protection and tourism revenues. Ironically, however, the main drivers of current reef decline—pollution, overfishing, sedimentation, and direct destruction—may be just as influential in the near term as climate drivers in the long term.

Van der Zande et al. (2020, p. 2203) were particularly gloomy about the effects of warming and acidification: Our results indicate that ocean warming and acidification under business-as-usual CO2 emission scenarios will likely extirpate thermally sensitive coral species before the end of the century, while slowing the recovery of more thermally tolerant species from increasingly severe mass coral bleaching and mortality. This could ultimately lead to the gradual disappearance of tropical coral reefs globally, and a shift on surviving reefs to only the most resilient coral species.

In some parts of the world, seagrass meadows can over time trap sediment, build upwards, and create various forms of reef. Seagrasses are marine flowering plants forming underwater meadows. This is the case with the Posidonia oceanica meadows of the Mediterranean (Bonhomme et al. 2015). These meadows have great value, not least for maintaining fish production (Unsworth et al. 2019) and for providing habitat for a variety of fauna, including Dugongs and Green Turtles. They may also play an underestimated geomorphological role. As Fonseca (1996, p. 263) pointed out, ‘The existence in many coastal areas of hundreds or thousands of hectares of seagrass beds seaward of the shoreline that can dampen waves, capture sediment, promote fining of sediments and export tons of organic material which modify

6 Coasts

sediment composition, provides all the attributes to modify shoreline processes both qualitatively and quantitatively’. However, they are highly vulnerable to human activities, such as pollution, nutrient runoff, and coastal development, and rank among the most threatened ecosystems on Earth (Waycott et al. 2009), with global loss rates accelerating from 0.9% per year in the 1940s to 7% per year towards the end of the twentieth century (Laffoley and Baxter 2016). Since the 1990s there has been some recovery of seagrass meadows in Europe due to management actions which have included improvement of water quality, reduction of industrial sewage, and anchoring and trawling regulation (de Los Santos et al. 2019). Some seagrasses, such as the Posidonia meadows of the eastern Mediterranean, may be threatened by rising seawater temperatures (Litsi-Mizan et al. 2023), and worldwide this seems to be an issue of some concern (Jung et al. 2023). Many species will show a contraction in their range (Daru and Rock 2023). Furthermore, SLR causes more wave energy to be received by seagrass communities, thus creating more damage to them (Tang and Hadibarata 2022). In many estuaries and bays, oyster reefs are an important component (Rodriguez et al. 2014; Zu Ermgassen et al. 2012). Created from aggregations of oysters, they support diverse and abundant ecological communities and underpin ecosystem services such as coastal protection, water filtration, fisheries productivity, and carbon sequestration (Howie and Bishop 2021). As Beck et al. (2011) have explained, centuries of resource extraction, exacerbated by coastal degradation, have pushed native oyster reefs to the brink of functional extinction worldwide. Overall, they estimated that 85% have been lost globally. However, attempts to restore oyster reefs have had some success (Goelz et al. 2020), and this has been helped by the spread of invasive Pacific oysters (Magallana gigas) which are rapidly expanding their global distribution across the historical distributions of native oyster taxa, whose reef habitats have been largely eradicated (McAfee and Connell 2021).

6.4.4 Salt Marshes In future, coastal marshes may be susceptible to a suite of influences: SLR, changes in storm frequency and intensity, increases in ambient temperature, ocean physical changes, including elevated sea temperature, and acidification (Morzaria-Luna et al. 2014; Fitzgerald and Hughes 2019). These wetland environments are potentially very vulnerable in the face of sea level rise (Gedan et al. 2011; Woodroffe et al. 2016), particularly where sea defences prevent the landward migration of marshes as sea level rises. In such locations what is termed ‘coastal squeeze’ occurs (Silva et al. 2020). As Fitzgerald and Hughes (2019, p. 508)

6.4  The Future

have pointed out, ‘Salt marshes formed in protected depositional settings during a period when the rate of rise was 0.2–1.6 mm per year. Their sustainability is now threatened by a rate of rise that is many times greater than when they were evolving, a rate that may outpace the marshes’ ability to add sediment and build belowground biomass’. Crosby et al. (2016) argued that without mitigation of greenhouse gas emissions salt marsh loss could exceed 90%, while Valiela et al. (2018) feared that 40 to 95% of the world’s salt marshes will be submerged by the end of this century. Sediment supply, both organic and inorganic, is a crucial issue. On coasts with limited sediment supply a rise in sea level will impede the normal process of marsh progradation, and increasing wave attack will start or accelerate erosion along their seaward margins. Marshes will attempt to move landwards, and where their hinterland is low lying, the salt marsh vegetation will tend to take over from freshwater or terrigenous communities. However, such landward movement is not possible where seawalls or embankments have been built at the inner margins of a marsh. However, salt marshes are very dynamic and in some situations may well be able to cope, even with quite rapid rises of sea level (Reed 1995). Indeed, Kirwan et al. (2016) have argued that in general, increased tidal inundation caused by rising sea level promotes more frequent and longer episodes of mineral sediment settling on the marsh platform, enhanced vegetation growth, and faster rates of organic matter accumulation. This feedback results in accretion rates that have accelerated in parallel with observed historical SLR. This is a conclusion supported by the work of Weston et al. (2023) along the eastern seaboard of the USA. Reed (1990) suggested that salt marshes in riverine settings may receive sufficient inputs of sediment that they are able to accrete rapidly enough to keep pace with projected rises of sea level. Areas of high-tidal range are also areas of high sediment-transport potential and may thus be less vulnerable to SLR (Simas et al. 2001). Likewise, some vegetation associations, e.g. Spartina swards (see Sect. 6.3.2), may be relatively more effective than others at encouraging accretion and plants are crucial for sediment accumulation (Cahoon et al. 2021). Conversely, marshes that may be highly susceptible to SLR include areas of deltaic sedimentation where, because of sediment movement controls (e.g. reservoir construction) rates of sediment supply are low. Such areas may also be areas of rapid subsidence. Microtidal marshes (