The Healing Power of Forests - The Philosophy behind Restoring Earth's Balance with Native Trees [First edition] 4333020735

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The

Healing er Pow of Forests

T he Phi_losophy behind Restoring Earth's Balaflce with Native Trees

This book was produced in collaboration with Professor Elgene 0. Box. The sections by Professor Miyawaki are excerpted from copy­ righted works published in Japanese under the titles Shokubutsu to Ningen (Plants and Humans) by Japan Broadcast Publishing Co., Ltd. and Midori Kaifuku no Shohosen (Medical Prescriptions for Restoring Forests) by Asahi Shimbun Company. We acknowledge with gratitude the editorial cooperation of the following persons: Margaret Suzuki, who translated the sections by Professor Miyawaki originally in Japanese; Professor Kazue Fujiwara of Yokohama National University, who checked the sci­ entific and common names in English of plants; and Dr. Shin'ichi Suzuki at the Japanese Center for International Studies in Ecology, who prepared the glossary. The photograph on the front cover depicts the environmental pro­ tection grove around the Oita Steelworks of the Nippon Steel Corporation in Oita Prefecture, Japan. Courtesy of Nippon Steel Cor­ poration. The photograph on the title pages shows a field around AEON Yachiyo-Midorigaoka Shopping Center in Chiba Prefecture, Japan, in which saplings of native trees were planted. After the planting, mulch (rice straw) was laid down to protect them then later to serve as fertilizer. Photos by Masayuki Tsutsui. Edited by Joy S. Sobeck and William Feuillan. Cover design and layout of photographs by NOBU. The text of this book is set in a computer version of Melior with a computer version of Optima for display.

First edition, 2006 Published by Kasei Publishing Co., 2-7-1 Wada, Suginami-ku, Tokyo 166-8535, Japan. Copyright © 2006 by Kasei Publishing Co.; all rights reserved. Printed in Japan. ISBN 4-333-02073-5

Contents

Prologue

g

Chapter 1: Forests and Civilization Forests Cover Only a Tenth of the Earth The Loss of Primeval Nature Forest Exploitation and the Vicissitudes of Civilization The Mediterranean Region Stripped of Its Forest The Summergreen Deciduous Forest Zone Clearing a Wilderness in One Hundred Years Growth in Limited Environments �uman Systems and Carrying Capacity No Virgin Forests Left in Asia Development and Over-Development Carbon and Global Warming Development and Conservation Dangers of Over-Development Human Beings Are Part of Nature Native Forests of Native Trees A Contrast with Japan Source of the Homeland Image 5

13 13 17 18 21

24 25 27 33 38

42 47 54 57 58 61

62 63

6

CONTENTS

Chapter 2: Communities of Living Things Biological Communities Balance in Natural Communities Actual and Abstract Plant Communities External Constraints on Plant Communities External Limitations Internal Regulation in Plant Communities Habitat Segregation Regulation: Summary Community Dynamics and Plant Strategies Optimal Locations May Not Be Optimal Plants and Humans Are More Than Just Similar Dead Centers Versatility May Not Pay in the World of Plants Quality and Quantity The Black Pine Groves on the Shanan Coast No Advantage to Being Too Strong The Leucaena Trees of the Bonin Islands Nitrogen Pollution by Civilization Chapter 3: Mantle and Fringe Communities Forests Destroyed by Roads for Tourism The Mantle Community Conditions for Growth of Mantle Communities Restoring Plant Life along Roads Beautiful Women and Clothes The Fringe Community Trees Planted Inappropriately Do Not Last Long Tropical Jungles Are Usually Created Artificially

65 65 67 68 69 72 75 82 84 85 85 87 88 90 90 91 93 94 97 101 101 105 107 109 110 111 113 115

CONTENTS Chapter 4: Temporal Vegetation Succession and Substitute Plant Communities Maintaining Existing Conditions Progressives and Conservatives How Plant Communities Succeed Each Other Pioneer Plant Species Climax-the End Product of Succession The Clements Succession Model Primary and Secondary Succession Progressive, Retrogressive, and Deviant Succession Substitute Vegetation Nature Is a Beauty with Perfect Taste Existing Vegetation Lasting Communities Vanishing Native Vegetation Natural Vegetation Potential Natural Vegetation The Relation between Substitute and Potential Natural Vegetation Potential Natural Vegetation Acts like a Mirror Ecological Plant Types What Is an Association? Mapping Actual Vegetation Mapping the Potential Natural Vegetation Chapter 5: Forest Reconstruction So-Called Greening Creating an Environmental Protection Forest

7 117 118 120 123 124 125 126 126 128 131 131 133 134 135 137 138 140 143 146 147 149 150 155 155 157

8

CONTENTS

The Need for Dedicated Program Directors Corporate Environmental Protection Groves Native Forests throughout the World Epilogue The Environmental Revolution Dilemmas in Human Ecology Societal Values and Business Values Global Change Sustainable Development? A Post-Sustainable World? Converting Tragedy to Recovery Scientific and Common Names of Plants Mentioned in the Book Glossary Additional Readings Index Photographs and special maps follow page 64

167 167

178 181 184 188 189 197 206 209 211

221 229 265 271

Prologue

On the morning of January 17, 1995, the Great Hanshin Earthquake suddenly struck Kobe and its surrounding area in western Honshu, Japan. The most modern and ostensibly strongest structures of concrete and steel toppled, including elevated expressways and bullet-train support pylons. Homes and other buildings collapsed, huge fires caused immense damage, and more than five thousand people lost their lives. At the time, I was in the mountains of Borneo, researching ways of regenerating tropical rainforests, and I saw the CNN television news reports when I came down to town. What flashed across my mind first was a question: "I wonder if the area at the foot of Mount Rokko suffered the worst damage from landslides." I feared that all the trees and groves there, which I had taught were useful in reducing disaster damage, had been destroyed. After returning to Japan I quickly made two field surveys of the affected area. Trembling inside, I boarded a helicopter to survey the damage and take aerial photographs before conducting inspections on the ground. In the neighborhood where the expressway supports had collapsed, I saw that the two lines of street trees were still standing, as tall as ever, amid the ruins of the city. Areas that had possessed few trees lay in shambles. The neighbor­ hood I had worried about, however, at the foot of Mount Rokko, was still surrounded by its original vegetation. Some damage was evident, such as fallen roof tiles, but fires had not penetrated the district and the trees were still standing. 9

10

PROLOGUE

On the reclaimed land at Port Island, some of the underly­ ing soil had liquefied, but even where retaining walls along the shore had broken, evergreen street trees such as oaks and species of castanopsis were unaffected. What impressed me most was that, in the neighborhood that had 'been burned to the ground by huge raging fires, even single lines and small groves of evergreen broadleaf trees had stopped the flames from spreading. On the side of the trees facing the fire, the thick, shiny leaves had turned brown. On the other side, though, they remained fresh and green, offering startlingly clear and visible proof of their effectiveness in fire retardation. Many old houses and other buildings were totally flat­ tened, so thoroughly collapsed that not even a cat could find its way out from under them. It is not surprising that a great many people were crushed to death. Where houses were sur­ rounded by trees, however, particularly evergreen broadleaf trees such as Japanese blue oak (Quercus glauca) or shira­ kashi oak ( Quercus myrsinaefolia), wild camellia, and ever­ green holly, the falling roofs and walls were often caught by the strong trunks and branches of the trees, opening spaces in the wreckage below. People in such houses no doubt had a better chance of escaping. In any neighborhood, forests made up of species native to the area· play a leading role in defining the scenery. They also serve as living green sanctuaries and places to relax for city dwellers who have scant opportunity to get close to nature. But these are not the only functions of such forests. The trees in Kobe showed us how useful they can be in fires and earthquakes, preventing flames from spreading into an uncontrollable blaze. Trees benefit us. in many other ways as well. Green plants, particularly the trees in forests, are the coordinators that keep natural environments and diverse biological commu­ nities in balance. It is vegetation, especially forests with mul­ tiple, complex layers of various trees, that controls a wide range of environmental processes and conditions, including the local meso- and micro-climate, appropriate circulation of

PROLOGUE

11

water, disaster prevention, and sudden, excessive prolifera­ tion or near extinction of animal groups. In these direct and indirect ways, trees provide an environment in which humans can live healthily and sustainably within the frame­ work of the natural system. Take, for example, the problem of carbon dioxide (CO2 ) emitted by automobiles and electric power plants. The CO2 that was in the atmosphere tens and hundreds of millions of years ago was concentrated in the forests of that time and eventually was buried underground, where it formed the basis for the coal, oil, and natural gas that we use for energy today. The increases in atmospheric CO2 that are now caus­ ing climate change on a global scale result from the burning of these so-called fossil fuels and from the CO2 released by extensive deforestation, mainly in the tropics, during the second half of the twentieth century. Although we must quickly find ways to reduce these CO2 emissions, we should also recognize that the best way to immobilize this carbon is to allow forests to absorb and fix it once more. This means that we need to create new for­ ests. The materials that make up the leaves, sterns, roots, and trunks of plants are collectively called biomass. Nearly 50 percent of plant biomass consists �f carbon. If organic mat­ ter, including roots, fallen leaves, and wood, is burned or otherwise oxidized, as by normal decomposition or decay, carbon is released into the atmosphere. The surest way to deal with this excess carbon we are creating-the underly­ ing cause of global warming and much of the other environ­ mental destruction we are now experiencing-is to place it under lock and key in those storehouses we know as forests. A forest has a total green surface area five to twenty times greater than that of an equal area of grass lawn. Wooded areas also function better than grass in mitigating noise pollution and damage from natural disasters, in purifying the air, and in maintaining water quality. The multi-layered structure of forests also reduces overall wind velocity, and the layers of trees act to filter out airborne particles. One hectare of common spruce can filter out 32 tons of dust and

12

PROLOGUE

dirt, while one hectare of Scotch pine (Pinus sylvestris) can filter out 35 tons. One hectare of European beech (Fagus sylvatica); a broadleaf tree that is the main component of most of the natural forests in Germany, can filter out 68 tons, nearly twice as much. The layers of forest trees also prevent raindrops from falling directly to earth, thus reduc­ ing their erosion potential. Fallen leaves and humus on the forest floor, together with the earth underneath, retain rain­ water and filter it. Natural beech forests are also reportedly much more effective in purifying groundwater than planted or more recent forests of red pine that have grown up in the poor soils of central Europe. In all these ways, then, trees and forests are essential to human life. The development of civilization can be sustain­ able only when humans, as one member of earth's total bio­ logical community, pursue life within the parameters of the whole system, without disturbing the natural balance. We can call the development of modern European civilization a history of human interference in the plant world. A review of this history shows us that simple-minded concepts and technologies that are not integrated into the balance of nature and the community of living things do not last long and have indeed been counterproductive.

Chapter 1 Forests and Civi I ization

Forests Cover Only a Tenth of the Earth Forests cover only 25 to 30 percent of the earth's landmass, about a tenth of the earth as a whole. They are found where precipitation is sufficient and generally appear in broadly east-west-oriented zones (see map on next page). There are three main types of forest. The first is the tropical rainforest, which contains the most diverse and colorful assemblages of wild species. Rainforests are located primarily in the three large equatorial land regions of the globe: the tropical Americas, equatorial Africa, and Southeast Asia. Concen­ trated in these forests is the bulk of the world's biotic gene pool, holding the genes of countless species that will proba­ bly be of great use to humanity in the future. The destruc­ tion of these tropical forests is one of the gravest threats to the global environment in the twenty-first century. The second type of forest is represented by several extra­ tropical kinds of broadleaf forest of Asia, Europe, North America, and smaller areas in the Southern Hemisphere. Broadleaf forests fall into two major categories: evergreen and deciduous. In evergreen broadleaf forests, most trees retain their leaves through the winter. In deciduous forests, trees drop their leaves during the unfavorable season, which may be a cold winter or the tropical dry season. Outside the tropics, deciduous forests are found in much of Europe, in

13

Map 1. World Vegetation Zones (after Heinrich Walter 1970) Natural vegetation and landscape types are determined largely by the global pattern of atmospheric circulation, which results in climate types that occur in more or less latitudinal zones. Vegetation types that correspond to these zonal climate types are also called "zonal"; they represent the world's potential natural landscapes and are the ecologi­ cal basis for human activity. These vegetation zones are shown on the map (the numbers correspond to Walter's climate types):

D 1 = Tropical rainforest D 2 = Tropical deciduous forest and woodland D 2a = Tropical savanna

3 = Subtropical desert and semi-desert 4 = Mediterranean forest, scrub, and shrubland 5 = Evergreen extra-tropical forest

_[}_ _______________ _

D 6 = Temperate deciduous forest D 7 = Temperate grassland D 7a = Temperate semi-desert and desert

■ 8 = Boreal coniferous forest ■ 9 = Polar tundra ■ 10 = Mountain areas

Extra-tropical evergreen forests include warm-temperate and subtropi­ cal evergreen broadleaf forests, such as the laurel forests on continen­ tal east sides (e.g., East Asia), as well as cool-temperate rainforests, usually broad-leaved, at higher latitudes on continental west sides (e.g., southern Chile; coniferous in northwestern North America). Mountain areas are not classified further at this global scale. (From: Walter, Vegetation und 1(/imazonen, © Verlag Eugen Ulmer, Stuttgart, Germany.)

16

FORESTS AND CIVILIZATION

parts of East Asia, and in eastern North America. Their main characteristic species are beech and oak. Evergreen broadleaf forests can be divided further into two main types: laurel and sclerophyllous. The characteris­ tic species of laurel forests have moderately large, dark-green leaves that look like shinier versions of the bay leaves used in Western cooking. Bay leaves (Laurus nobilis) are from the laurel genus (Laurus), so we call this kind of shiny, dark-green leaf a laurophyll (laurel + phyll, the latter from the ancient Greek word for leaf). Typical laurel-forest trees in East Asia include species from the laurel family (Lauraceae), especially the genera Persea (also called Machilus), Beilschmiedia, Cinnamomum, and Neolitsea; the tea family (Theaceae), such as Schima and Camellia; laurophyll trees from the oak family (Fagaceae), including evergreen oaks (Quercus), Lithocarpus, and the important East-Asian genus Castanopsis (shii in Japanese, the host trees of shiitake mushrooms); and other trees with similar leaves, including some magnolias. Laurel forests are found in southern Cnina, the southern half of Japan, along the south coast of Korea, and in some mountains of subtropical Asia (especially the Himalayas); they are also found in other humid warm­ temperate to subtropical areas of continental east sides, especially southern Brazil and much of New Zealand. Ever­ green broadleaf forests of the other type, sclerophyllous (hard-leaved), are composed of trees such as cork oak and olive, which have hard, smaller, sometimes narrow leaves adapted to dry summers. These forests are found especially around the Mediterranean Sea and in similar dry-summer climates on the midlatitude west sides of other continents, including much of California and smaller areas of southern Australia, central Chile, and southwestern South Africa. The third main type of forest is the northern conifer for­ est, found across northern Eurasia (Scandinavia, European Russia, and Siberia) and northern North America (most of Alaska plus northern Canada). Most conifers have relatively long, narrow leaves shaped like needles, which are covered with a protective waxy cuticle. Characteristic coniferous trees

THE LOSS OF PRIMEVAL NATURE

17

include spruce, fir, and pine. Most are evergreen, but decid­ uous larches occur in the coldest areas of Siberia. Conifers generally have straight trunks and softer wood than broad­ leaved trees. Thus they are popular as ornamental trees, and their wood is especially useful as lumber for many purposes. The Loss of Primeval Nature From an objective point of view, humans are just one spe­ cies in the natural world. Several million years have passed since the evolution of the first primitive humans. As long as humans did not differ much from wild animals in way of life and population density, their intervention in nature must not have been significant. It is no more than twenty thousand years ago, very recently in the long course of human history, that humans began significantly affecting other biological communities and nature as a whole. In the Lascaux limestone caves of southwestern France and in a limestone cave in Altamira on the northern coast of Spain, there are cave paintings twenty to twenty five thousand years old that depict the bison and deer that people hunted. It was probably around this time that humans began to affect nature in ways different from other animals. In Europe dur­ ing the Later Stone Age, no more than ten thousand years ago, humans began to transform nature significantly through their early efforts at agriculture. When we review the development of civilization, we find it to be a history of confrontation with nature. To survive through the ages, humans had to cope not only with heat, drought, storms, volcanic eruptions, and various climatic, geographical, and topographical elements of the physical environment, but also with all the rest of nature-large forests, wild beasts, and so on. Nowadays, to protect just a tiny wooded area, we solemnly debate changes in develop­ ment' projects such as highways and city streets. In the past, however, forests were among humans' most formidable ene­ mies, feared because they were dark, contained wild animals, were believed to harbor spirits, and were easy to get lost in.

18

FORESTS AND CIVILIZATION

Especially in Japan, people had a feeling of awe and respect for natural plant communities and for forests in particular. At first people did not choose to live in dense forests, inste,ad preferring open spaces, such as those by the sea or rivers. Because early humans lived by hunting and gather­ ing, they favored areas with mixed vegetation at the edges of forests. The rapid destruction of primeval nature most likely began when humans learned to use fire. People set fires to clear forests and grasslands; as agriculture developed, they replaced the original vegetation with crops of single plant species; they also domesticated animals and pastured their flocks in forests as well as in grasslands. These practices reduced forests to scrub, savanna, or treeless steppe. The impact of human activities on nature diverged from the impacts of other creatures and from natural phenomena, becoming significant enough to reduce grasslands to deserts and wastelands. Forest Exploitation and the Vicissitudes of Civilization Although humans conquered green environments, devel­ oped civilizations, and converted natural forests to open landscapes (and sometimes to deserts), their halls, temples, forts, and palaces have eventually fallen into ruins, like sand castles washed away by the waves, and whole peoples and cultures have vanished. This process can be seen clearly in the rise and fall of the ancient civilizations of Mesopotamia, Egypt, and the Roman Empire. In aerial photographs of the vast desert covering Iraq and Syria, where Mesopotamian civilization once flourished, we can see the remnants of agricultural fields and ridges cre­ ated several thousand years ago. In the eastern Sahara, once home to the great civilization of Classical Egypt, the desert is estimated to be two and a half times larger now than it was four thousand years ago. In central Africa's tropical rain­ forest and semi-evergreen seasonal forest, where there is a moderate dry season, overuse has converted natural forests

FOREST AND THE COURSE OF CIVILIZATION

19

into savannas and scrub. In South America and Australia, much land has been degraded and some forests have been completely destroyed in the name of development. The Romans cut down the natural forests in Italy and throughout the Mediterranean region to build the ships in their navies, and the soil has since eroded further through fires and over­ grazing. Now, after more than a thousand years, reforesta­ tion has become very difficult, and large expanses of barren red-brown earth are visible everywhere. Elsewhere in Europe, from the seacoasts up into the Alps, long-term human intervention has devastated the original natural environment. The only remaining virgin forest in central Europe is thought to be that in the Swiss valley of Derborence. In China and Japan, also homes of ancient civi­ lizations, much of the original natural environment has similarly been destroyed; now, in the early twenty-first cen­ tury, it is almost impossible to find any of the original vege­ tation. The total devastation of natural forests in exchange for the development of civilization may simply be the sad fate of the relationship between man and plants. In nature, nitrogen-loving annual plants, such as fireweed (Erechtites hieracifolia), sprout quickly over forest areas that have just been logged and grow more than one meter tall. This happens because the leaf litter that has accumulated on the forest floor breaks down all at once after the tree cover is removed, bringing about abnormally high levels of nitrogen in the soil. For the two or three years during which this condition persists, the fireweed completely dominates the area, its countless white fruits crowned by long pappi. When the nutrients are all used up, fireweed disappears completely, moving on to colonize another logged area. If we had a time-lapse film of the movement of civiliza­ tions, we would see that, like the fireweed, they suddenly flourish in one place until they use up the natural resources there, and then they die out. Over time, centers of civiliza­ tion have moved from Egypt to Mediterranean Europe, to China, to northern Europe, and eventually to the Americas. As we can see in the Mediterranean region that was home

20

FORESTS AND CIVILIZATION

to the "sclerophyll cultures" of Mesopotamia, Egypt, Greece, and Rome, almost all the forests have disappeared as a result of cultural practices, especially agriculture. Much sci­ entific research clearly demonstrates this fact. In North Africa, for example, aerial photographs show remains of dikes indicating the former existence of agricultural fields in the middle of what is now the Sahara desert. The drying and desertification of this area since Classical times was caused partly by exhaustion of the productive landscape, which in turn contributed to a drying of the climate. These processes finally made it impossible for people to go on liv­ ing there. All human activity changes the carrying capacity of a landscape, that is, its ability to restore itself, to regenerate productive vegetation cover, to buffer the effects of the out­ side environment, and to provide the many ecosystem serv­ ices on which human societies have come to depend (such as provision of foods and materials, cycling and cleansing of water, and maintenance of stability). Sometimes carry­ ing capacity may increase for a short period of tim_e, as new technology is applied or certain previous impediments to productivity are removed. Over longer periods, though, as population grows and people become more dependent on their land and their technologies, the effects of their extrac­ tion activities cause accumulating stress on the lc!-nd and on its productive capacity. Such environmental degradation may take the form of overgrazing, overextraction of ground­ water supplies, soil erosion or compaction, poisoning of the soil by toxic substances, nutrient depletion, or many other forms. In any form, though, degradation reduces the carry­ ing capacity of the land. Because the detrimental effects of land use may not appear immediately, there are time lags before the human population can react-if indeed it reacts at all. More complex systems have longer time lags. Thus, while the population increases, the environment is becom­ ing degraded and carrying capacity may be decreasing. Such opposing trends may bring the system to a critical imbalance fairly quickly, causing a "crash" of the type experienced by

THE MEDITERRANEAN REGION STRIPPED OF ITS FOREST

21

the Maya of pre-Columbian Central America, whose large cities disappeared rather suddenly. Large systems, how­ ever, may be too complex to crash and instead may simply decline gradually and inexorably, like the Roman Empire, with its parallels to today's situation. Our capacity to dam­ age both the global and local environments is suggested by the equally inexorable increase in the size of the human population and by its projected future size (see fig. 1).

The Mediterranean Region Stripped of Its Forest In order to build the imposing Egyptian, Greek, and Roman civilizations of classical antiquity, much of the green cover of the Mediterranean region was destroyed. For more than five hundred years, the Roman Empire extended from cen­ tral and northwestern Europe to North Africa and to the interior Middle East. By the fifth century, when the Roman Empire was overthrown, the original forests of the Mediter­ ranean coastal regions, forests of evergreen oak (mainly holly-leaved holm oak, Quercus ilex), were already largely gone. Even in the late twentieth century, if you had looked down from an airplane at the Mediterranean areas of Italy, Greece, Spain, France, and North Africa, you would have seen degraded, sometimes completely bare, red-brown land­ scapes extending in every direction. If you conduct field surveys in southern Italy or Spain, you will note that there is a thin growth of pasture. On close examination, however, you will find that this is noth­ ing more than sparse patches of shrubs and herbaceous plants with thorns and hard leaves. This is the characteris­ tic degraded landscape called garrigue, which is the result of more than a thousand years of overgrazing. Seedlings and even saplings of potential overstorey (canopy) trees are · trampled underfoot, and all the edible shrubs and herba­ ceous plants are eaten down to the roots. The only plants that can manage to hang on through this scourge of live­ stock grazing are thorny or poisonous plants that sheep and goats cannot eat.

Figure 1. Human population growth 14 ....---------------------,-----------, 12

/

v,10

········.. .................... ·······/·····

C

.2

8

8

�

6

C 0

:J 0.

g_

/'

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High Medium

............... ············ '· _._ �·�·· Low 7, .... _

�....:.. ....

4 2 0

11 ----------11 ....------,------,------,------,-----�/1 ....------,------,------,------,------,------,-----+---,------,------,-----�

> 2 million

years ago

1800

1950

2000

2050

year

For most of human history population levels were relatively low, reaching about 1 billion only around 1800. The 2 billion mark was reached around 1922, and growth accelerated noticeably after 1950, reaching 4 billion by 1974 and 6 billion by 1999. The graph also shows low, medium, and high population projections to the year 2050; they range from 8 to 11 billion, as estimated by the United Nations Population Division (World Population Prospects: The 2000 Revision, 2000). All these projections assume some degree of deceleration in growth; at the current rate of growth, world population would reach 13 billion by 2050.

I have often observed how the huge flocks of sheep and goats in places like Sicily or the foot of the Spanish Pyrenees impede the recovery and re-growth of vegetation. One herds­ man and a group of s];ieepdogs herd a flock of ten to fifteen thousand sheep and goats, moving slowly across the land­ scape as they eat up every shred of the sparse vegetation in

THE MEDITERRANEAN REGION STRIPPED OF ITS FOREST

23

their path. With just a slight movement of his staff, the herds­ man sends sheepdogs running around the flock like a squad of police, and with great efficiency they move the herd in the desired direction. Mixed in among a flock of ten thou­ sand sheep may be three hundred or so black goats. Tied to the neck of each goat is an empty can that makes a melodi­ ous clinking sound. Like a military band, the goats move among the ranks of sheep, helping keep the herd in line. The short-legged sheep eat all the plant sprouts, leaving nothing behind. The black goat musicians have longer legs and can stand or jump three meters or so to reach the shrub or tree branches that have escaped the teeth of the sheep. With their skillful jumping the goats can leave the area completely denuded in the twinkling of an eye. After the merry passage of the herd, moving at about one kilometer per hour, with the sound of clinking cans echoing across the hillsides, every bit of green growth has been eaten up or trampled down, leaving exposed the bare earth, which in many cases is an old, previously laterized (permanently hardened), rough, red-brown surface. Southern Europe's climate has dry summers and wetter winters, a pattern called Mediterranean. Rainfall comes mainly in the season least suitable for plant growth, and the climate is not the best for tree growth in general. Compared with the evergreen laurel forests of Japan and other parts of East Asia, where there is plenty of rain in summer, Medi­ terranean sclerophyll trees are shorter, have smaller and thicker leaves, grow more slowly, and may be bent or twisted. The dual practices of burning and permitting live­ stock to forage in forests rapidly degrades the secondary re­ growth and may reduce such areas to bare ground. On hillsides stripped of woody vegetation, many areas are badly eroded, having lost their soil to runoff water that fell in winter when there was less vegetation to protect the soil. After the soil, the foundation for plant growth, has been washed away, the Jurassic limestone and other ancient underlying substrates are exposed. At this point it becomes

24

FORESTS AND CIVILIZATION

extremely difficult to bring the forest back again, especially when the growing bushes and herbaceous plants are repeat­ edly eaten by flocks of sheep and goats. In countries such as Italy, France, and Spain, the govern­ ments, research institutes and various other organizations whose members include ecologists and plant sociologists, have been trying for decades to restore the vegetation, in particular by replanting forests on the bare mountains. They have found it more difficult than they expected, however, and have had only limited success because the topsoil has been eroded away. Also, because the natural vegetation of these areas has been so thoroughly degraded, it is impossi­ ble to determine the composition of the original vegetation, or of the current potential natural vegetation (that most suit­ able to the climate and soil after the erosion), which would be the most appropriate vegetation for replanting. The Summergreen Deciduous Forest Zone

About ten thousand years ago, after the last glaciers receded, the natural forests of Europe and North America gradually migrated northward into their current positions. Most of Europe (except the Mediterranean lowlands) and eastern North America became covered with virgin summergreen forests, that is, forests of deciduous broadleaf trees that are green in summer but bare in winter. In both regions, the main trees are species of beech and deciduous oak. Now, in the early twenty-first century, the northernmost limit of these forests in Europe is in central Sweden, extending sporadi­ cally to the vicinity of Uppsala, about an hour by train north­ west of Stockholm. Oak forests also now extend to central England, but beech only reaches southeastern England. The Roman Empire also included some of this deciduous forest zone. After the empire fell, the leadership of conti­ nental European civilization shifted gradually from the Latin peoples, whose way of life was adapted to the sclero­ phyll forest, to Germanic and Slavic peoples dwelling in the cooler summergreen broadleaf forest zone. Human

CLEARING A WILDERNESS IN ONE HUNDRED YEARS

25

destruction of nature and of natural forests advanced at the same time into this zone. The virgin summergreen forests of central Europe, including especially the European beech­ oak and oak-birch forests, were largely cut down by about AD 1000 and are thought to have been almost completely destroyed by about two hundred years ago. The main causes of the destruction were burning to clear the land and the pasturing of livestock in forests. Because of the high latitude and consequently unpredictable grow­ ing seasons, meat has always been central to the European diet. The next step after the hunter-gatherer way of life was a quasi-agricultural civilization. Even after the agricultural mode was adopted, animal husbandry continued to be one of the most important vocations in European society. After burning a forest, people kept immense flocks of sheep, goats, cattle, horses, and even pigs in the area, letting them feed in spring and summer on the young green shoots. These same forests were usually also being managed for timber and fire­ wood by pollarding (periodically lopping off whole large branches) and coppicing (cutting of whole stems, which causes multiple main stems to re-sprout from the stumps). The practices of burning and pasturing livestock in these already stressed forests gradually reduced their height and eventually annihilated them. Clearing a Wilderness in One Hundred Years North America also has a history of forest destruction. The natural forests of this broad continent vary with location. Forest zones corresponding to Europe's deciduous broad­ leaf forests of beech and oak are limited to the areas around and just southeast of the Great Lakes. The main forest types in this area are northern oak forests, American beech-sugar maple forests, so-called mixed mesophytic forests with many tree species, and other northern hardwood forests. To the south, wide areas of (also deciduous) oak-hickory forest and forests of southern mixed hardwoods extend almost to the coast of the Gulf of Mexico. A conifer forest zone

26

FORESTS AND CIVILIZATION

stretches across much of Canada; other conifer forests occur in the Appalachian Mountains, around the northern Great Lakes, and in the various mountain ranges of western North America. The history and level of human interference in the natural plant life of each area also varies with the nature of the vegetation. The first human effects on the deciduous forest in eastern North America, beginning in the distant past, were those of Native Americans. Axes, knives, and other metal implements have been discovered throughout the region and are thought to have been used as far back as 5500 BC. Like indigenous peoples on other continents, the Native Americans lived mainly in forests and near bodies of water. More than a century after the European discovery of America, the first permanent English colonies, at Jamestown (Virginia, 1607) and Plymouth (Massachusetts, 1620), initi­ ated the large-scale migration of Europeans to the Americas. The new arrivals introduced their agriculture, and by about 1760, as they cleared land for cultivation, destruction of the American forests began in earnest. Europe and Asia developed gradually over long periods, from the Stone Age through the Bronze and Iron Ages, and the dominant way of life changed from hunting and gathering to agriculture. By contrast, the development of the North American Great Plains in the nineteenth century was very rapid, made pos­ sible by the invention of machinery suited to large-scale agriculture. The destruction of natural environments forged ahead at a rapid pace. Particularly during the first stages of bringing land under cultivation, extensive tracts of natural forest were deliberately burned and cleared. During the sin­ gle year 1871, about twelve thousand square kilometers of forest along the Michigan and Wisconsin rivers were cleared by burning. Large tracts of old-growth forest probably remained, mainly in the Appalachian Mountains, but by the twentieth century most of these had been wiped out by logging or forest fires. After the burning and clearing, not all the land was used for agriculture. Most of it was left unused or was cultivated for only a short time. Areas burned by

GROWTH IN LIMITED ENVIRONMENTS

27

wildfires became and remained secondary forests or waste­ lands of weedy plants. The Great Plains were once the habitat of the buffalo, a wild native ungulate. Having established a beachhead in the eastern deciduous broadleaf forests, settlers moved westward, not only destroying forests and prairies, but also slaughter­ ing the buffalo herds beyond the settlers' needs-indeed almost to extinction. The buffalo had benefited the indige­ nous people in many ways. Nevertheless, approximately one million buffalo were shot and killed by a handful of settlers in the three years beginning in 1872. The American histo­ rian Francis Parkman (1823-1893) wrote that, by the latter nineteenth century, almost nothing temained of the buffalo but their bones, and the land they had grazed was being grazed by cattle or left as boundless pasture. Settlers from Europe viewed the American continent as an unlimited supply of forest, wildlife, and other natural resources for exploitation. From the late eighteenth to the early nineteenth century, reckless development, deliberate burning, and massive slaughter of wildlife resulted in wide­ spread destruction, including a reduction of old-growth forests to one-fifth of their former area, the near extinction of the buffalo, and the near disappearance of the beaver, which was trapped for its pelt. Growth in Limited Environments

Whenever humans encountered unsettled or sparsely set­ tled lands, these new environments seemed limitless. We can now see that this was not the case. In fact, growth in limited environments is the rule both in human settlement and in other ecological systems, and it quickly became a focus of study by early ecologists. Beginning in the nineteenth century, scientists began to develop concepts of growth in limited environments, culmi­ nating in the so-called sigmoid (S-shaped) model of popula­ tion growth shown in figure 2. According to this model, a population at low density relative to the space and resources

Figure 2. Population growth in a limited environment

� C

0

�:J

B

Q..

0

C

time When far from resource limits, populations grow rapidly in an acceler­ ating fashion (positive feedback). This is sometimes described as "exponential growth," as at the left in the graph. If the population feels its resource limitations and responds in a perfect, density-dependent fashion, growth continually slows (negative feedback) as the popula­ tion approaches its limit (carrying capacity). This is represented by the so-called sigmoid curve (logistic model) shown in the main graph and in inset A. In reality, however, populations of more complex organisms usually overshoot their resource base. If the overshoot is moderate, as in inset B, population size and carrying capacity may adjust to each other and reach a sort of dynamic equilibrium (the balance fluctuates within limits). If the overshoot is too great, however, as in inset C, the resource base is degraded and carrying capacity decreases, followed ultimately by a population decline or crash.

provided by its environment will grow rapidly at first and more slowly as population density increases. As the popu­ lation becomes larger, there are more parents to produce more offspring, so population growth accelerates, as indi­ cated by the initial upswing in figure 2. As the population increases, however, there is progressively less and less space

GROWTH IN LIMITED ENVIRONMENTS

29

and/or resources for each individual, and members of the population begin to feel the limitations of their environment. In theory, but depending very much on the particular species involved, the rate of population growth begins to decrease as population density becomes greater and resources become scarcer. These resources, or limiting factors, which are the most effective constraints on growth, might be something as simple as light and water in a growing stand of plants. For animals, the important limiting resources might be food, water, shelter from predators, and structures or materials that can provide homes for rearing young. The slowdown in growth as resources become scarcer is shown toward the right in figure 2 (after a theoretical mid-point that mathe­ maticians call the inflection point). If the organisms feel their environmental limitations sufficiently, fertility will decline and growth will slow down, such that the popula­ tion size gradually levels off just below a theoretical limit that ecologists caU the carrying capacity of the particular environment. This sigmoid model (also called the logistic model) illus­ trates the fundamental system concept of feedback. Feed­ back is a kind of cause-effect relationship that permits those who have done something to know or feel the results. In a diagram of the dynamics of a system (as in fig. 3), feedback can be shown as a closed loop, in which effects flow from the original agent through various results and back to the original agent. In the early stage of population growth, the rapidly increasing number of offspring quickly provides more parents, so population growth accelerates. This is an example of positive feedback, because it amplifies the origi­ nal action. In this sense, all growth represents positive feedback. The rate of population growth is determined by factors such as the number of offspring produced in a brood and generation time (the time between the start of one gen­ eration and the start of the next). Rabbits, for example, reproduce quickly, because they produce several offspring at once and the generation time is relatively short. If, however, the results· of an action cause the original

30

FORESTS AND CIVILIZATION

action to diminish, this is called regulatory feedback or neg­ ative feedback, because it reduces the original action and brings the system back toward its earlier condition (self­ regulation). A good example is the thermostat that regulates room temperature: if the room becomes too warm, the ther­ mostat senses this and turns on the air conditioner; if it becomes too cool, the heating system goes on. In the sig­ moid model, as the population begins to feel the growing scarcity of resources, parents begin to have fewer offspring. The population, though still increasing, grows in a density­ dependent fashion, that is, more slowly. Negative feedback is important because it keeps a system within bounds, in a state that is at least fairly close to equilibrium. If a system has positive feedback mechanisms that are not balanced by negative feedback mechanisms, it will grow out of control. In the real world, simpler organisms follow the sigmoid model more closely than do bigger, more complex organ­ isms, such as larger animals and humans. Bacteria growing on agar in a petri dish, for example, sense their diminishing food supply very quickly and follow the sigmoid model almost perfectly. An expanding patch of roadside weeds feels the reduction in available light (and perhaps water) as its leaves start to. shade each other, and its growth slows rap­ idly as it becomes dense. (As a result, of course, the ecologi­ cal strategy of weeds is to produce many lightweight seeds that can find and colonize new environments.) More complex organisms, however, often do not feel their environmental constraints as quickly or as effectively as do simpler organ­ isms. This phenomenon may be due to longer life spans, the ability to substitute one resource for another, complex behavioral patterns and social environments, and various other factors that buffer these organisms somewhat from direct environmental dependency. In particular, the time lags inherent in more complex systems represent a major obstacle to effective feedback. As a result, in complex sys­ tems that involve larger organisms, including humans, the system momentum is often so strong that populations grow well beyond the environmental carrying capacity, at least

GROWTH IN LIMITED ENVIRONMENTS

31

temporarily. This overshoot, as it is sometimes called, has important consequences because it strains the productive and other functions of the supporting environment and may eventually reduce its carrying capacity. Some ways in which a population may approach and adjust to the carrying capacity of its environment are illus­ trated in the insets in figure 2. Simpler species adjust their fertility rates based on population density and may approach carrying capacity smoothly, as in inset A. It is much more common, however, for even relatively simple organisms to overshoot their limits to some extent, causing at least some temporary reduction in supporting resources. If the over­ shoot is not too great, these populations may come into some sort of dynamic balance with their environments, as sug­ gested in inset B. If the overshoot is large, however, there may be a significant reduction in the environment's sup­ portive capacity, often referred to as environmental degra­ dation. A degraded environment will not recover unless the population load is reduced. As a result, the degradation may gain a momentum of its own and become permanent, with a continuing decline in carrying capacity. This is illustrated in inset C, in which carrying capacity and population size gradually spiral downward toward some new balance at an often much lower level. What does environmental degradation mean in the real world? Signs of degradation may be obvious, such as soil erosion, population collapse due to toxic contamination, or direct destruction of productive forests or farmland. Less conspicuous but also visible might be other consequences of pollution (such as disease), general losses of biodiversity, or increased "weediness" of the landscape. Even before these symptoms become apparent, however, more subtle stresses may be altering various aspects of ecosystem structure, such as the balance among different species populations, and basic ecosystem processes such as photosynthesis, repro­ duction, and water and nutrient cycling. These changes in turn impair the many services that healthy ecosystems pro­ vide to us humans, including food and materials, clean

32

FORESTS AND CIVILIZATION

water, and maintenance of landscape stability. The term ecological integrity refers to the health of ecosystems in this functional sense, that is, the completeness of their structure and their ability to perform normally their full range of nat­ ural processes. The term biodiversity has often been under­ stood simply as the number of species (species richness), including the weeds, present in a geographic area. More recently, the protection and maintenance of biocomplexity (not only species diversity), including ecosystem functions and the natural balance among ecosystem components, has replaced preservation of biodiversity alone as the goal of conservation planning and implementation. The following list of forms of ecological degradation, with examples in parentheses, was prepared by ecologists in the 1980s and gives an idea of the complexity of the problem: • Changes in primary productivity (for example, reduced forest growth due to acid rain) • Extinction or severe reductions in populations (as when forest clear-cutting eliminates habitat for other species) • Rapid population increases or "blooms" (such as by algae in streams, or by weedy alien species) • Stunted growth or increased death rates (for instance, fish kills due to pollution) • Changes in reproductive capability (such as failing egg­ shell development due to DDT) • Altered genetic mutation rates or survival rates of geno­ types (for example, resistant strains of diseases arising due to overuse of antibiotics) • Changes in host-parasite relad.onships (as when pollu­ tion-weakened pines are attacked by bark beetles) • Damage to normal organismal functions (for example, birds covered by oil spills losing the ability to regulate body temperature) • Lost control of water flow and storage (as when removal of vegetation increases runoff and decreases storage) • Changes in detrital decomposition rates (for instance,

HUMAN SYSTEMS AND CARRYING CAPACITY

33

when erosion reduces soil microbes and thus recycling rates) • Transformations in nutrient storage capabilities (such as nutrient leaching and loss due to over-irrigation of crops) • Biological concentration of toxic substances (as when trace metals accumulate upward in food chains to carni­ vores) • Changes in chemical exchanges between land and water systems (like those due to erosion and siltation resulting from poor agricultural methods) • Changes in chemical exchanges between earth-surface systems and the atmosphere (for example, when excessive nutrient inputs, such as eutrophication in lakes, cause algal blooms that consume available oxygen and may then cause methane to be released) • Changes in succession rates or patterns (as when fire sup­ pression permits undergrowth to expand, thus reducing climax species) Human Systems and Carrying Capacity The concept of carrying capacity was perhaps first used in livestock and wildlife management but has also been applied to human-settled landscapes, as in Garrett Hardin's (1968) well-known description of the "tragedy of the com­ mons." In Hardin's example, local herdsmen are free to pas­ ture their animals on the village grazing commons and to sell their products at the local market. If one herdsman increases the size of his herd, and the other herdsmen fol­ low suit, they bring on the ruin of the commons through overgrazing. Resources that are owned by no one but are available to everyone are subject to this kind of overuse and have come to be called common-pool resources (or public goods in the field of economics). Examples include rivers, rangeland, the oceans, and the atmosphere. It is very important to note that we do not have to rely on greed or ambition to explain the tragedy of the commons-

34

FORESTS AND CIVILIZATION

it would occur even without these human factors. In theory, in a perfectly static environment (and without greed or ambition), a system may remain in equilibrium. But envi­ ronments change, for example, through year-to-year differ­ ences in weather, and these changes affect the productivity of the commons. As soon as one herdsman (or one compet­ ing airline, publisher, or other big company, for that matter) notices that a competitor has been favored by a change and may thus have at least the potential to increase his share of a quasi-finite market, to the possible detriment of others, the first herdsman will be sorely tempted to react by increasing his own capacity. Expanding the size of his herd potentially brings the individual herdsman greater income but costs him essentially nothing, because the cost (pasture damage through overgrazing) is shared by all. So if one herdsman enlarges his herd, the others are constrained to do the same. The "tragedy" is thus not necessarily caused by greed but rather by competition, which may be entirely unwanted but is an inherent attribute of the system. In other words, there is a sort of systemic determinism arising from the structure of the system (in this case, a free but limited resource, a quasi­ finite market, and the lack of any higher authority or hierar­ chy among the users), which locks the individual herdsmen into a competition that pre-determines the outcome, namely, degradation of the resource. The existence of a higher author­ ity could potentially suppress the competition and prevent the degradation. The cost that is not borne by the individual herdsmen but rather foisted off on others (or on the. envi­ ronment, or even on future generations) is called an exter­ nality. For human systems, carrying capacity can be defined a little more completely as the number of people that can be supported by an environment, indefinitely, and without ongoing environmental degradation. This definition is �ome­ what redundant, since the idea of indefinite support requires that there be no continuing degradation that reduces the supportive capacity. Even so, in practice it is useful to rec­ ognize all three components explicitly: the number of indi-

HUMAN SYSTEMS AND CARRYING CAPACITY

35

viduals, indefiniteness, and lack of environmental degrada­ tion. What factors determine carrying capacity in human systems? They may be extremely complex. For example, limiting factors in the capacity of cities to support more and more people may include the ability of local governments and resource bases to provide such necessities as water supplies, sewage facilities, schools, and jobs. Hardin (1986) also suggested that human societies have a kind of "cultural carrying capacity" which is necessary to provide the flexi­ bility needed to adapt to new situations. In order to study, and perhaps anticipate, some of the dynamics of human systems, we can put these concepts and functional patterns together into a system framework, albeit a theoretical and quite simplified one. Such a system model, represented by a diagram of components and func­ tional links between them, is shown in figure 3. In a sys­ tem model, major functional components are called state variables; the model attempts to simulate their behavior by simulating the functional relationships that link them. Simulation is useful because the feedback loops can be so complex that one cannot otherwise anticipate their conse­ quences. The simple heuristic model in figure 3 has five main com­ ponents: the levels of human population, available resources, technology, environmental degradation, and carrying capac­ ity. The main functional properties of the system include both relatively direct and more complex feedback linkages. Growing human populations have their own demographic momentum which, in a cybernetic sense, represents fairly simple, direct positive feedback. Technology and resource availability also tend to "grow" in the sense that higher lev­ els of both promote new discoveries and ever more effective technology for extracting more resources. Environmental degradation can also have a momentum of its own and thus some positive feedback independent of the detrimental impacts from other parts of the system. Each of these direct effects is represented in the diagram by a "self loop" (with a plus sign indicating positive feedback). More difficult to

Figure 3. Population growth, carrying capacity, and environmental degradation Population (P)

increases automatically as long as resources are not limiting-and maybe even then; its increase leads to a need for better technology (T) to pro­ vide more food and other resources (R).

Resources (R)

resource availability (and use, i.e., depletion); more needed to support larger population (P) but may also lead to environmental overuse and deg­ radation (D) unless controlled; can be expanded by technology (T).

Technology (T)

advances with human experience (rarely decreases) but very unpredictably, revolutioniz­ ing economic and social organization; its increase provides means for greater resource exploitation and for higher carrying capacity (CC).

Environmental Degradation (D)

increases with overuse of resources (R), espe­ cially when populations take resources from their environment faster than they can be replenished (i.e., carrying capacity is exceeded).

Carrying Capacity (CC)

ability of a self-managing, quasi-natural envi­ ronment (land area or sea) to support biotic populations by supplying needed resources (food, materials, nutrient cycling, water man­ agement, etc.).

The figure shows a heuristic model relating human population size and carrying capacity as well as levels of resources, technology, and envi­ ronmental degradation. The effects of each variable on the others are shown in the table and also in the system diagram, in which the arrows connecting the variables represent cause-effect relationships. A plus sign (+) represents a positive relationship (an increase in the first vari­ able causes an increase in the second), and a minus sign (-) represents a negative relationship (an increase in the first variable causes a decrease in the second). Dashed lines represent slower, intermittent, or

Effects of variables on each other

cc

p

R

T

D

+

( +)

(+)

+

R

+

(+)

(+)

Technology

T

+

+

(+)

(+)

Envl. Degradation

D

+

-

Population

p

Resources

Carrying Capacity

cc

+

(;) _____ (+)

(+)

,,�l� )

+ " ;

(+):

\

I

...:,, (

(0

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+ (J +)

-

- > CC P (+)

Growth loops (positive feedback): single-component: P- P, T- T, R - R, D - D multi-component: P- T - CC - P Regulatory loops (negative feedback): none Result: uncontrolled growth (P - T- CC - P loop) damages environ­ ment (D) in an accelerating manner, leading to the eventual col­ lapse of carrying capacity (CC).

otherwise weaker relationships. A closed loop with only positive rela­ tionships represents a growth loop (positive feedback). A closed loop with a minus sign represents a potential regulatory loop (negative feed­ back)-but there are none. As a result, the causal structure of the sys­ tem results in uncontrolled growth, which exhausts the resource base, degrades the productive capacity of the environment, and leads to either a collapse or a slower decline in carrying capacity. The longer decline would probably result in more environmental damage than the collapse.

38

FORESTS AND CIVILIZATION

visualize and to manage, of course, are the more complex 'causal linkages and their effects on carrying capacity. One can attempt to understand the behavior of the system by identifying all the causal loops (closed cause-effect link­ ages) in the system. In this model the causal loops are as follows: • Growth loops (positive feedback): o single-component: P - P, T - T, R - R, D - D o multi-component: P - T - CC - P • Regulatory loops (negative feedback): none Even without quantifying the rates or magnitudes of the components or functional linkages, one can see that this system is inherently unst.able. It has no regulatory mecha­ nisms to counteract the growth loops that occur in several areas and whose effects on environmental carrying capacity are compounded through their complex interactions. What is missing in such diagrams is a way to represent the time component-and time lags may be the most dangerous aspect of most systems, because more complex systems gen­ erally have longer time lags. We have already seen that time lags can have a very destabilizing effect on a system. One might construct the model differently, depending on one's own biases, but such models are instructive only if one is realistic and attempts to represent the situation holistically.

No Virgin Forests Left in Asia Turning now to Southeast Asia, home of the rainforest, we find that by the late twentieth century there were almost no remaining virgin or primary forests, in the strict sense. In Thailand, for example, between 1978 and 1986, our group surveyed the mangroves (the so-called marine forests) at 2,800 locations, from the Andaman coast along the Gulf of Siam almost as far as the Cambodian border. On December 26, 2004, the mangroves were damaged by a giant tsunami generated by a massive earthquake off the west coast of

NO VIRGIN FORESTS LEFT IN ASIA

39

Sumatra. Although Thai scholars had told us that this land­ scape was "virgin forest," we found only one area where the trees reached thirty meters in height. Even most of the "floating forests" of mangroves in the sea were already wasteland. Although the mass media and others have claimed that Southeast Asia's forests are all being destroyed by Japanese companies, according to our field surveys this is not neces­ sarily the case. It is true that until the 1960s there was reck­ less logging in which whole forests were cut down or burned just to obtain one or two large lauan (Shorea) trees per hectare. Since the 1970s, however, only trees more than eighty centimeters in diameter at breast height have been cut. Results of our surveys show that a forty-meter-tall parent tree of the dipterocarp family produces more than 1,500 seedlings. Thus, if the large tree is carefully cut and taken out without harming any of the surrounding trees, there are plenty of seedlings waiting for a chance to grow up, mean­ ing that natural regeneration is quite possible. When we surveyed Phuket Island, on the west coast of southern Thailand, we found a luxuriant mangrove forest twenty to thirty meters tall at the seashore; behind it was a vast, thick tropical rainforest that included Hopea tree species. We could see towns and villages scattered here and there in the forest and a few sandy beaches along the shore. Many trees had been cut down in the process of developing the island for tourism. At the time of the tsunami, Phuket had become a world-famous resort, and many thousands of tourists as well as local people were killed by the enormous waves. If developers had left some forest in place, the tsunami would not have caused as much damage. The man­ grove forest would have dissipated the force of the waves somewhat, acting as a green buffer and allowing people a chance to escape from the waves or at least to grab onto the trees, using them as a lifeline. An even greater enemy of the Southeast Asian forest than tourism-related development is uncontrolled, shifting, slash­ and-burn agriculture, which at the prevailing high human

40

FORESTS AND CIVILIZATION

population densities revisits the same areas before they have time to recover. Most of the mountainous areas of Thailand and Cambodia experience a dry season lasting almost half the year, from autumn to spring. These areas used to be covered with evergreen broadleaf forests. With the excep­ tion of part of one national park in Thailand, however, most of the forests have been eliminated by the slash-and-burn agriculture practiced during the dry season. Even the origi­ nal fifty-meter-tall trees in the overstorey layer have been cut down. When these forests are burned and the area is planted with upland dry-field rice, the first harvest is exceptionally abundant. In the rainy season, however, the soil nutrients are leached out and even the soil itself, which accumulated over a long period of time and was held in place by a living network of roots, is washed away. Thus, after the second or third year, the area is no longer produc­ tive and is abandoned as wasteland. In this way rich sites are swiftly degraded. For long afterward the natural forest is incapable of restoring itself, and the area becomes cov­ ered by a lower deciduous forest and by wild sugarcane (Saccharuum spontaneum var. arenicola) growing more than two meters tall. Alang-alang grass (Imperata cylindrica) a meter tall covers areas where repeated erosion of the fer­ tile topsoil in the rainy season has made the land infertile. At the highest elevation in Thailand, on Mount Doi Inthanon (2,500 meters) near the border with Myanmar (Burma), there are also evergreen broadleaf forests. Pastured in these forests is a breed of Burmese cattle that lives on a very rough diet and destroys the forest. Removal of the forest-floor vegetation through the pasturing of livestock or through fires degrades the taller trees as well, and the forest becomes mere brush. This process happens throughout the world. What is the state of natural forests in China? Most ecolo­ gists at the Academy of Sciences of China (the Academia Sinica) say that Shanghai, Beijing, and other plates were originally grassland. Our field investigations there, how­ ever, show that these areas were altered by humans and may

NO VIRGIN FORESTS LEFT IN ASIA

41

have been forested at some point within the past ten thou­ sand years. We looked in particular at a place called Tiantong, near Ningbo (south across the estuary from Shang­ hai). This low coastal mountain area is covered by a splen­ did evergreen broadleaf forest, something that can hardly be seen anywhere else in the Nanjing-Shanghai-Hangzhou area. The forest is protected as a national park because it sur­ rounds an old Zen (Ch'an) monastery complex with ninety­ nine rooms, said to have been built 1,200 years ago. From the presence of rice-paddy terraces in the lowlands and on the hillsides, as well as tea plantations, one can tell that this area is in the evergreen broadleaf forest zone. There are also some groves of thick-stemmed bamboo (Phyllostachys). The results of our floristic survey of the temple forest at Tiantong showed that it is not true, as is commonly held, that poplars and willows (Salicaceae) and black alders are the only trees that grow in China. Rather, a much richer, more diverse ever­ green laurel forest once grew there, composed especially of species of Persea and other laurel-family trees, and species of castanopsis and evergreen oak, all with dark, glossy, evergreen laurophyll foliage. In exchange for the four thou­ sand years of Chinese civilization, the natural forests have almost completely disappeared. The Chinese have cut down most of the forests deep in the mountains; those that remain are so remote that one has to walk for several days to reach them, because the roads are too narrow for cars. Near the Great Wall, north of Beijing, reforestation is being vigorously promoted but so far is not very successful. Near Beijing, what forests remain are still being destroyed. In low­ lands around the Forbidden City and in other places, the only trees are the mume plum (Prunus mume) and oriental persimmon (Diospyros kaki). The mountains are bare, and there is mostly wasteland as far as the eye can see. Chinese scholars also say that there never was a· forest on the site of Beijing. But if you take your backpack and go deep into the mountains behind old temples, where hardly anyone ever goes, you will find (deciduous) Mongolian oaks (Quercus mongolica), which could have been the main species of the

42

FORESTS AND CIVILIZATION

ancient forest flora. Thus we can conclude that this area for­ merly was a deciduous broadleaf forest. As we have seen, virgin forests are disappearing around the world. A:p.yone observing this with his or her own eyes will feel the urgent need to restore forests. Development and Over-Development

Historically, human efforts to transform nature have been gradual processes of trial and error over long periods of time, varying, of course, with the cultures, economic systems, and levels of technology involved. From a global point of view, these changes were moderate enough not to destroy the overall ecological balance. Modern exploitation of natural resources and development of industrial processes, however, are very different from earlier human interventions in nature, not only in scale but also in quality. Innovations in earth­ moving equipment have made it possible, in a few short years, to make changes in the earth's topography that would once have taken centuries. Chemical compounds released by industry and consumption are continuously altering the essentials of life, air, soil, and water. These changes are so far-reaching that they are modifying the fundamental prop­ erties of these basic elements. Since about 1900, rapid developments in chemistry and technology have enabled the production of countless chemi­ cal fertilizers and other substances which have been spread constantly, not only on farmland but everywhere else as well, including meadows, mountains, and urban areas. Since World War II, immense volumes of such artificial chemicals have been distributed throughout the globe, from the most civilized countries to the depths of tropical forests. These compounds include DDT, BHC, and 24 D (a herbicide that kills by stimulating a plant's cell-dissolving function), sulfur oxides, mercury compounds, and various antibiotics. These amazing scientific discoveries can wipe out the toughest insect pest or render the most tenacious diseases harmless­ but they can also kill the strongest trees.

DEVELOPMENT AND OVER-DEVELOPMENT

43

The Japanese have been wedded to the evergreen broad­ leaf forest since the dawn of their history, as demonstrated by archaeological remains from the Asuka period (AD 593710). Parts of China show a similar history, and as a result, the civilizations of Japan and China are sometimes called laurel-forest cultures. After the destruction in World War II, however, modern development proceeded rapidly in Japan, as did consequent environmental destruction. Bombed-out cities, formerly composed mainly of wooden structures, were rebuilt with enormous quantities of concrete, steel, and synthetic petroleum products. In other words, urban­ ization and industrialization advanced through the use of inanimate materials. Because this mode of development has progressed all too smoothly, at least outwardly, we have forgotten our sense of gratitude to living natural materials and have even lost the ability to distinguish between things that are alive and things that are not. By creating an industrial model, converting it to numeri­ cal measurements, and entering those numbers into a com­ puter, we can produce millions of identical television sets, lightweight portable CD players, cars, and other standard­ ized consumer goods. This type of industrial production has been misunderstood as the most modern way of doing everything, and it has come to be applied to all aspects of society, from landscaping to (even more inappropriately) education and personnel management. This tendency has brought about a kind of one-sided development that is based on principles of economics and empty functionalism. In our pursuit of production, urbanization, and industrial­ ization, we have forgotten or have come to ignore the fact that our family members and associates are living beings. As a result, serious environmental pollution has occurred and people's lives have been endangered. Some of the better­ known incidents of severe pollution or contamination in Japan include the copper poisoning of the Watarase River in the 1880s by the Ashia Mine in Tochigi Prefecture; the cadmium poisoning of the Jinzu River in Toyama Prefecture in 1950, resulting in itai-itai disease (a painful softening of

44

FORESTS AND CIVILIZATION

the bones, accompanied by kidney failure); the mercury poisoning of the waters off the coast of Minamata in Kyushu in 1956 (a disgraceful incident notorious worldwide); and the poli"ution of air and water in the 1960s by the large petrochemical complex in Yokkaichi, in Mie Prefecture, that caused what we call "Yokkaichi asthma." The word development is used rather loosely to refer to many kinds of activities which are generally thought of as constructive, ranging from local road or housing construc­ tion to the building of large industrial complexes or of extensive infrastructure such as communications or trans­ portation systems. Comprehensive attempts, usually by gov­ ernments, to improve the condition of whole populations, such as through education, job opportunities, or better stan­ dards of living, may also be referred to as development. Except for these more general efforts, though, most of what is called development, especially locally, is essentially entrepreneurial activity by so-called developers and their associates in the business community who want to make often large profits by building something that can be pre­ sented as necessary or at least good. Consider the example of forest or farmland on the periph­ ery of a city. As the city grows, the· land on the periphery becomes more valuable because it can be portrayed as essential for new residential areas or other facilities. It is also more valuable to developers, middlemen, and other involved businessmen because more valuable land calls for larger construction projects and brings a greater profit in real-estate transactions. As the market value of the land increases, the pressure on the landowner to sell the land to the developers (and make a profit himself) becomes greater and greater, until finally he sells out. As the amount of peripheral land remaining shrinks, its market value also increases. Local governments are powerless to resist this eco­ nomic imperative, because their constituents may benefit from the new jobs (some of which may be permanent) and from other associated economic activity. (The government itself may also be constituted by businessmen, who profit

DEVELOPMENT AND OVER-DEVELOPMENT

45

from the transactions directly or indirectly.) In this way, the productive land around a city is doomed to become "devel­ oped:'-that is, built on and gradually built up (generally with inanimate materials). In the process, the formerly pro­ ductive land cover is converted to one that cannot maintain itself, as a natural system can, but instead requires human management (and the consequent infusion of money-but probably yielding someone a profit), perhaps for a very long time. This is just one example of the forces, some quite cybernetic in nature, that are at work in economic systems and that are made more powerful and less tractable by com­ plex feedback relationships. Profit-oriented business is not necessarily bad, of course, because growth is often necessary. Development, in this sense of local and larger construction projects, however, is not an activity that is designed to look at all aspects of a sit­ uation and do what is best for the whole system. It is a single-purpose activity that may be quite indifferent to conflicting considerations, especially in free-market systems operating in a general climate of "growth is good." Such development has the potential, to come at the expense of society in general and to the detriment of the productive natural or quasi-natural environment that ultimately sup­ ports it. Since the mechanisms for regulating such economic activities are generally weak and compromised, the result is ultimately "development" beyond what is really needed: sprawl, urban deserts, and, in a word, over-development. Development on the national level is also subject to pow­ erful economic forces, especially when businesses become powerful enough to dictate national policy. Demands for energy and other resources to support industrial and other business activity have caused wars in the past and will cause even more in the future as resources become globally scarce. Of course, not everyone is oblivious to these facts; consideration of resource demands and of the possibility of less energy-demanding lifestyles began seriously in the 1970s (for example by Schumacher 1973 and Lovins 1977; see "The Environmental Revolution" in the epilogue of the present

46

FORESTS AND CIVILIZATION

volume). William Ophuls (1977), in a remarkable book called Ecology and the Politics of Scarcity, wrote of the "Faustian bargain" required when a society commits to the dangers of nuclear power as a means of satisfying its energy demands. Finally, given the concept of carrying capacity and the environmental consequences of exceeding it, ecologists and well-intentioned businessmen alike have recognized the concept of sustainable development, that is, development that can be sustained by its supporting ecosystems over the long term without damaging their productive and other functional capabilities. Japan's prosperity in the later twentieth and early twenty­ first centuries has been based partly on a history of living in harmony with nature. The natural forests that nurtured the Japanese and encouraged the nation's growth, and the tradi­ tion of living in harmony with them for more than two thousand years, however, have both shrunk dramatically in just the last few decades. If the trend continues, the Japa­ nese will end up living a life completely divorced from trees and other natural plants. When that time comes, will we Japanese still have the same potential for unlimited development? When the southern Europeans of the sclero­ phyllous forest zone completely destroyed their natural forests, they were forced to cede the leadership of Western civilization to the northern Europeans of the deciduous broadleaf zone. Can we absolutely guarantee that we will not find ourselves in a similar situation? The forests ofJapan and most other parts of the world are now in the greatest peril of unrestrained conversion and devastation. The large­ scale logging of deciduous broadleaf forests during the 1960s, their complete conversion to conifer plantations, and the construction of roads for tourism right up to the peaks of high mountains all threaten to eliminate Japan's few remaining natural areas. Great numbers of vacationers instinctively flee cities where no green forests remain, which leads to construction of more tourist facilities in the mountains, which in turn encourages more and more visi­ tors and construction, in a vicious circle.

Carbon and Global Warming Since the middle of the twentieth century, it has been appar­ ent that human activities affect not only landscapes and the earth's vegetation cover but also the global atmosphere, to such an extent that this impact has changed the earth's energy balance and climate. A physicist might describe it as follows. Electromagnetic radiation is a form of energy that travels in waves. Light is one form of this radiation; it has wavelengths that our eyes can see. A much wider range of radiation (energy) is emitted by objects all the time, how­ ever, at wavelengths that are invisible to us. In fact, all mat­ ter in the universe (solid, liquid, and gaseous) continuously gives off electromagnetic radiation, while also receiving such radiation from surrounding matter. If a body (or a liq­ uid or a gas) absorbs more energy than it loses (mainly by re-radiation), then it has a net gain of energy and heats up; if it loses more energy than it absorbs, it cools off. Tempera­ ture is a measure of this internal energy content. The radiation emitted by the sun (sunlight) that reaches the earth's surface is partly reflected and partly absorbed. As shown in figure 4, the earth also gives off radiation; clouds absorb some of it, and the rest returns to outer space. Emitting this so-called longwave radiation (or earth radia­ tion) is the only significant way the earth has to get rid of the energy it receives from the sun and keep itself from over­ heating. If the earth does not re-radiate an equivalent amount of energy back to outer space, then the earth-atmosphere sys­ tem heats up. The earth's atmosphere absorbs some of the outgoing longwave radiation, in essence trapping it within the earth-atmosphere system and causing a natural green­ house effect, without which the earth would be almost as cold as Mars. Some gases in the earth's atmosphere, how­ ever, especially carbon dioxide (CO 2 ), trap the earth's out­ going longwave radiation very effectively-but not the incoming solar radiation. Any increase in CO 2 causes an unnatural increase in the greenhouse effect, sometimes referred to as the enhanced greenhouse effect. This is what

Figure 4. The greenhouse effect ,1/ -0/1'

L • is normally small-10% of Lt under clear skies and-80% of Lt even under heavy overcast. "Greenhouse gases" such as CO2 and CH4, however, selectively absorb Lt wavelengths (but not K • or K t) and re-emit increased L •. Solar radiation (Kt ) comes through the earth's atmosphere relatively unimpeded, and is then partly absorbed and partly reflected (U) at the earth's surface (darker and rougher surfaces absorb more). Under natu­ ral conditions, this solar input is balanced by earth's outgoing (infrared) thermal radiation to outer space, which, however, is emitted not only from the earth's surface (Lt) but also from all levels of the atmosphere, some upward and some back downward (L •) toward the surface. The fact that this re-radiation occurs at all levels results in higher earth tem­ peratures than if the earth had no atmosphere, actually about 33 ° C higher. This is the so-called greenhouse effect and is a natural aspect of the earth's atmosphere. The outgoing thermal radiation, however, is effectively absorbed by greenhouse gases in the atmosphere, such as carbon dioxide, methane, and water vapor. The more of these gases the atmosphere contains, the more energy it absorbs; this causes the lower atmosphere and the earth's climate to heat up. This is the enhanced greenhouse effect that produces global warming.

CARBON AND GLOBAL WARMING

49

we are experiencing now. Many people think that the CO 2 is trapping sunlight, but in fact it is the outgoing longwave radiation that is being trapped. The importance of CO 2, and of the global carbon budget, can be appreciated when one realizes two things: (1) plants may consume CO 2 and release ("produce") oxygen during photosynthesis, but they (and all animals) also release CO 2 when they breathe, a process called respiration; and (2) all decay and burning processes, collectively called decompo­ sition, consume oxygen and release CO 2 . In photosynthesis, plants absorb carbon during the day and fix it into various carbohydrates and lignin (the main structural material in plants). Why do living plants then release CO 2 ? For the same reason that animals do: to metabolize (oxidize) some stored carbohydrate, a process that provides energy for mainte­ nance and growth. The CO 2 that plants absorb is fixed as biomass, becoming the roots, leaves, stems, and trunks of plants. Dead biomass decomposes, as when dead leaves decay and logs rot on the forest floor. The cut wood used in construction also slowly breaks down, releasing CO 2 to the atmosphere. Another familiar decomposition process, which releases CO 2 much faster, is burning-for instance, the burn­ ing of wood, coal, oil, or gas. During the Carboniferous period (around 350 to 280 mil­ lion years ago) and the Jurassic period (some 195 to 135 million years ago), forests composed mainly of tree ferns grew up, accumulating large amounts of carbon in their biomass. In time these immense forests died and were buried and locked away in the earth, gradually becoming coal, petroleum, and natural gas, today's fossil fuels. In ways that we still do not completely understand, the global carbon cycle maintained its balance over hundreds of mil­ lions of years through the separate but complementary nat­ ural workings of the oceans, organic life in the soil, and atmospheric CO 2 , The steam engine was invented near the end of the eigh­ teenth century, and humans were soon mining and burning fossil fuels to power the Industrial Revolution. Combustion

5Q

FORESTS AND CIVILIZATION

of these fuels produces energy, but it also releases CO 2 into the atmosphere. As a result of fossil-fuel use and other human activities, the amount of CO 2 in the atmosphere has increased by more than 30 percent since the beginning of the Industrial Revolution. The increase since 1958, when measurements began, is shown in figure 5, along with high, intermediate, and low estimates of atmospheric CO 2 levels in the future. The rise in atmospheric CO 2 levels also affects other global processes. For example, more CO 2 in the atmosphere means that more longwave radiation is 'trapped in the earth-atmos­ phere system (the greenhouse effect); this raises tempera­ tures, especially in winter and in the colder, high-latitude continental (polar and sub-polar) regions of the world. Melting of the Antarctic ice cap has now been clearly docu­ mented. As an ice cap melts, its off-white surface area, which reflects most of the sunlight it receives, decreases, and there is a corresponding increase in the area of darker land and water, which absorb most of the incident sunlight. This greater energy absorption in the polar areas raises their temperature further, causing more melting, in an accelerat­ ing growth loop (a positive feedback process) that consti­ tutes a sort of vicious circle. Higher temperatures also cause more water to evaporate into the atmosphere, creating more cloud cover and greater potential for storms. These are just two of the more obvious feedback results of the small initial warming caused by greenhouse gases (and perhaps some other factors). Such feedback loops can become very com­ plex, and they are poorly understood, especially the time frames that may be involved. For example, due to the long time lags in the system, we may already have warmed the polar regions enough to melt the polar ice caps by 50 per­ cent or more by sometime in the coming centuries. It may already be too late to stop this from happening-and we don't know whether that is the case. Carbon dioxide is not the only greenhouse gas. Some other gases, such as methane, are even more effective per molecule in trapping the earth's outgoing longwave radia-

Figure 5. Increase of carbon dioxide in the earth's atmosphere since 1958 380 370

E

360

-�0

C

350

u

340

C

0

u

6 u

330 320 310

1958

'70

'80

year

'90

2000

Measurements of atmospheric carbon dioxide were begun by Charles Keeling in Hawaii in 1958, at which time CO2 content was estimated at 315 ppm (parts per million). Atmospheric CO2 appears to have been about 275-80 ppm for several thousand years before the beginning of the Industrial Revolution around 1800. It has now risen to about 370 ppm, increasing about 1 ppm per year (more in recent years) due to net CO2 release to the atmosphere, primarily from burning of fossil fuels and tropical deforestation. At the current rate, atmospheric CO2 is projected to double to around 750 ppm by the year 2100. Atmospheric CO2 traps outgoing thermal radiation from the earth to space, causing the earth-atmosphere system to heat up (the enhanced greenhouse effect, or global warming). (Scripps Institution of Oceanography, repro­ duced by permission.)

tion. Many of these other greenhouse gases are also increas­ ing in the atmosphere, but they remain much less abundant than CO 2 • So CO 2 is the main concern, and it is very impor­ tant for scientists to understand and monitor the earth's entire global carbon budget of flows and storages, in the atmosphere, in fossil-fuel reserves, and in other carbon

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FORESTS AND CIVILIZATION

"pools" such as biomass and the ocean. It also becomes urgent to find ways to take CO2 out of the atmosphere and store (sequester) it elsewhere. One possible way to sequester carbon (advocated espe­ cially by industrial countries with large forest areas, like the United States, Canada, and Russia) is to let it accumulate in land vegetation, that is, in forests. Carbon makes up about half the weight of biomass (excluding the water content). In the late twentieth century, the total volume of plant bio­ mass on land, and thus carbon storage on land, was esti­ mated to be about 550 to 650 gigatons of carbon (gT C, or 10 9 metric tons), a bit less than the amount of carbon resid­ ing in the earth's atmosphere (about 750 gT C, almost all as CO2 ). But forests cannot grow everywhere, because trees have a relatively large surface area (mainly leaves) t:qa_ t loses water, and some climates do not provide enough rain­ fall to compensate for this water loss. Some years ago the junior author developed a simple model of plant metabolic processes (photosynthesis and respira­ tion) as driven by climatic conditions. It was used to simu­ late the potential growth of vegetation worldwide, until it reaches local equilibria with climate. In a growing vegeta­ tion stand, the production process (photosynthesis) reaches its maximum soon after the forest canopy (or other over­ storey) is more or less fully developed. However, the con­ sumption process (respiration) increases with the increasing amount of biomass that must be maintained. Equilibrium is eventually reached, and the forest (or other vegetation) stops accumulating biomass. The accuracy of this global simula­ tion was assessed by comparing predicted biomass amounts with the amounts actually measured in many parts of the world. The resulting maximum biomass potentials of the world's land areas are shown on the map in figure 6 (see color pages). According to this simulation and the map, the total global amount of carbon that mature forests could potentially hold, at equilibrium with climate, would be about 1,700 gT

CARBON AND GLOBAL WARMING

53

of carbon. This amount could never be reached, of course, because factors such as soil poverty or recurring distur­ bances limit forest growth in some places. Nevertheless, the difference between the potential and actual amounts of car­ bon stored in land vegetation (perhaps about 800 gT C) is similar to the amount of ·carbon that is in the atmosphere now. It is also roughly the amount that will be added to the atmosphere by human activity over the next century or so if the atmospheric CO2 level doubles, a scenario that is com­ monly used by scientists and one that current and foresee­ able trends strongly suggest is realistic. So it seems to some that we could theoretically put this extra CO2 into forests. In reality, though, sequestering any significant amount of carbon in land vegetation, mainly in forests, requires aban­ doning that land and letting it grow up, over a hundred years or more, into something approaching its forest poten­ tial-while we all live in the desert areas. Our already excessive and still rapidly growing human population (and aggressive, profit-driven exploitation systems) certainly will not do this. At this point one more dogma should perhaps be dispelled, namely the unquestioned belief that "trees produce oxygen." The oxygen that plants release through photosynthesis is at least partly balanced by the oxygen they consume through respiration. For growing trees (and other plants), there is indeed a net "production" (release to the atmosphere) of oxygen and concomitant storage of carbon. In mature and maturing trees and forests, however, there is very little mar­ gin between production and consumption, and such trees are no longer growing enough to be significant net produc­ ers of oxygen (or starers of carbon). Unfortunately, one can­ not just cut down the trees and replace them by young, growing trees in order to continue producing oxygen and storing carbon. This is because any gains from such a proce­ dure would be offset by the oxygen consumption and CO2 release from the natural decomposition of the dead biomass of the felled trees. Even treated wood used in construction

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decomposes, albeit more slowly, releasing CO2 and con­ suming oxygen. Physical and chemical changes in the living environment are happening on a much larger scale and at a more rapid pace than humankind has experienced so far. Thus, no one can predict the direct and indirect effects these changes will have on the environment and on living creatures, including humans. Even if one new development out of many happens to work to the detriment of the fundamental conditions for life, it will have an effect on humans that cannot be foreseen accurately. One thing we must be partic­ ularly cautious about is that even if each individual factor -in environmental change has only a small impact and imper­ ceptibly small effects on the human body, when the effects of a variety of factors accumulate and are compounded, there is danger of a fatal outcome. DEVELOPMENT AND CONSERVATION

After Japan lost most of its industries, housing, transporta­ tion, and other man-made infrastructure in a short period of time during World War II, the nation's watchword became "development." Industrial development, land-use develop­ ment, regional development, and so on were to set our poor, cramped country back on its feet. Governments at all levels, from local to prefectural and national, were overflowing with the sincere desire to attain economic and industrial stability by developing Japan's scarce natural resources. The feeling was that "development" was the vigorous and youthful bat­ tle cry of a generation striving to rise up from the depths of military defeat. By the late 1950s, when Japan's economy had improved to a relatively comfortable level and various programs to use forest resources and develop tourism were underway, the country's industries had recovered so well that they attracted the attention of the entire world. The fruits of a number of

DEVELOPMENT AND CONSERVATION

55

development programs began to appear in the 1960s as the growth of industry and the quickening of economic activity. At the same time, a few people began to realize that the other side of this coin was the rapid change or loss of natu­ ral vegetation in urban and industrialized zones, and even loss of the soil and topography that provide the environ­ ment for natural ecosystems. Even the people who noticed these changes, however, did not have a sufficient understanding of how elimination of natural vegetation from human living environments creates a situation so intolerable as to threaten habitability. Sud­ denly, dragonflies, cicadas, and fireflies disappeared from among us, together with pests such as mosquitoes and flies. Birds no longer visited our gardens. The disappearance of these members of the integrated biological community was a warning to human beings, who are members of the same community. The disappearance of the living green environ­ ment from our midst, day by day, was a kind of silent protest against the loss of balance around us and the damage to the life-support system of all living things. In recent years, those creatures most insensitive to the destruction of their own living environment, namely humans, have finally begun to feel that something is amiss. We have started to experience a vague fear as the nearby hills, once cloaked in green, expose their sad red-brown interiors, and valleys once brilliant with the autumnal yellows and reds of Japa­ nese maple (Acer palmatum) and Japanese zelkova (Zelkova serrata) are filled up with earth. If, finally, we move into a newly constructed public­ housing apartment complex, for the first time we feel the security of living in a palace of steel and stone, a reinforced­ concrete home. But after two or three years, the white ceil­ ing starts to impart a strange sense of incompatibility, a sort of fretfulness, and unconsciously we begin to feel that we have to get out and go to the beach or the mountains, any­ place where trees and wildflowers are growing. The expression "conservation of the natural environment"

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first began to appear in print in Japan in the 1960s. It is unlikely that people at that time understood that natural vegetation and calls for the conservation of nature were indispensable to the security of the foundations of their own existence. Rather, people began to advocate the conser­ vation of nature mostly from a romantic point of view, based on the feeling that life was less enjoyable without insects and birds, or the sense that natural vegetation was being reduced to miserable, sparse fragments of a uniform aspect. By the late 1960s, however, people could no longer ignore the fact that the air, water, and even the soil of their own neighborhoods were becoming polluted. The leafy shade of the forest was being replaced by the shadows of skyscrapers, factories, and new transportation facilities such as expressways and elevated bullet-train tracks. If people went out in their leisure time to search for natu-· ral landscapes in the mountains or by the sea, they found the roads, trains, and buses packed to overflowing with other people on the same quest. And when they finally reached the shore or the mountains, they found so many other people there with the same idea that it seemed as if the traffic jams and congestion of the city had been trans­ ferred wholesale to the country. By the late twentieth cen­ tury the situation had become even worse. It is as if the crowds are scrambling to flee from a spreading blaze, climb­ ing desperately onto jam-packed trains headed toward the little patches of remaining nature, where people from every walk of life grab at their tiny allotments of leisure to rush out of the city. This phenomenon is one result of Japan's comprehensive development, which has been pursued in every sector dur­ ing the many decades since the end of World War II. If the purpose of development is to build a pleasant and healthy life for people in the present and to ensure our lives for the future, what we have been experiencing for some time now is the era of over-development. Finally, even among the Japanese, one begins to see signs of irritation, perhaps

DANGERS OF OVER-DEVELOPMENT

57

with ourselves, and a trend toward self-reflection about the "development is almighty" approach to life. Dangers of Over-Development For some considerable time into the future, science and technology will no doubt go on bringing forth a wide array of new chemicals and machines. That most avaricious crea­ ture, the human being, will never be satisfied with merely producing enough food. Ephemeral as thfse goals might be, we will no doubt continue trying to make life easier, more convenient, and more enjoyable-and, for some, simply more gratifying in rather mindless ways. We will likely employ vigorously the abundant tools of technology and civilization to create featureless, artificial, computer-mod­ eled environments to satisfy our material desires-the most convenient and functional environments possible, in which no one would need to sacrifice or persevere in anything. But before such a state of completion is reached, we and our society will probably have lost both the power to sur­ vive and the capacity to develop a new civilization. This ultimate failure is inevitable because human life is governed by the same natural laws that govern the lives of all other species. And the greatest danger in the world of living things, whether it is a community of roadside weeds or plagues of locusts or field mice, is a state of over-devel­ opment. When the ideal conditions for a certain plant or animal species have been stable for a certain period of time; its population can grow explosively, allowing it to domi­ nate an area. In nature, though, the new plant environment created by such overpopulation cannot be sustained, and another plant community will take over. Let us properly understand the severe social system of the biological world, in which a creature that alters the living environment and completely overcomes the coexisting members of its community will die out in its turn. Humans are already pursuing a course that is too destructive of the

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environment that supports all living creatures. We are wip-_ ing out too many of our coexisting living beings, the con­ stituent members of biological communities: the plants, insects, birds, microorganisms, and other creatures that are necessary for us to live better lives. The destructive forces are so strong that the amount of forest wiped out in a matter of decades in the earth's three great tropical regions is roughly equivalent to the amount already destroyed over the course of two thousand years in the temperate regions. At the same time, in the advanced countries and all over the world, natural environments are disappearing rapidly around industrial areas, transportation centers, and residential districts, in particular where there once were woodlands and forests. In times like these, it is imperative to conserve both primary forests and other natu­ ral forests close to their original state in both the tropical regions and the temperate regions, especially in urban areas. In 1988 Science magazine reported that, even if the forested area of the globe were doubled, it would postpone the global environmental crisis for only thirty to fifty years, if we continue living as we do now. Even if this grim assess­ ment is accurate, we face a situation in which we must endeavor seriously to recover, repair, and re-create the forests that have existed until recently. For us to live well and healthily now and in the future, we must correctly understand the invisible yet diverse, functional, complex, and indirect relationships that link plants and people. Human Beings Are Part of Nature When we examine the fundamentals of the relationship between humans and nature, we face perennial questions. From very ancient times, people have asked what human­ kind is and what nature is. Most people who have discussed this question, as is evident from the thinking of many philosophers, have viewed humans and nature as being in opposition and have tried to resolve the question anthro-

HUMAN BEINGS ARE PART OF NATURE

59

pocentrically. From the standpoint of the modern natural sciences, however, especially ecology, humans are just one element of nature. Although human beings are the most highly developed creatures in nature, we cannot survive in isolation from other living things, outside the system of the biological community. Among the earth's species, humans are in a weak posi­ tion. This is because, in an ecological context, we are con­ sumers at the top of the food chain. We can see that the volume of living beings on earth is insignificant compared with the volume of the planet, but living organisms do play an important part in the earth's material cycles, on land and in the atmosphere and oceans. The activities of liv­ ing organisms, including ingestion of nutrients, growth, reproduction, and occupation of space, are related to and affect the earth's material (biogeochemical) cycles. August Thienemann classified living things as follows: producers (such as green plants), which create organic matter out of inorganic elements; consumers (mainly animals, including humans), which live on this organic matter; and decom­ posers (such as bacteria and fungi), which break down organic matter. The major structural elements of plants and animals are those that also make up the atmosphere: oxy­ gen, hydrogen, carbon, and nitrogen. Other structural ele­ ments are also vital for living creatures, but in much smaller amounts. Carbon constitutes about one-tenth of all organic matter on earth. This amount is equal to about one-third of the car­ bon in the atmosphere. Green plants convert solar energy to chemical energy by photosynthesis, using the chlorophyll in their leaves. In the process, atmospheric carbon is bound into organic matter. Part of the carbon in the organic matter created by green plants is recycled into the atmosphere as CO2 from the respiration of animals (and plants) and the breakdown and combustion of organic matter. Another por­ tion of the carbon in biomass remains as humus in the soil, some of which hardens into peat or coal, thus becoming

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part of the earth's crust. The net balance of these material processes has a decisive effect on the amount of CO2 in the air, which in turn affects climate. One of the global problems we face today is shortages of water, which accompany the rapid development of industry and civilization. The bodies of all living creatures consist largely of water, and water is involved in the life processes of almost all organisms, so the existence of living creatures is fundamentally connected to the earth's water cycle. As we can understand from the examples of the carbon and water cycles, the activities of living creatures affect the earth's inorganic processes in many ways. We can also see that the ability of large earthmoving equipment to remove whole geological strata, fill valleys and estuaries, and create new topography upsets the balance of various material cycles in wetlands, which results in further alterations to or limitations on the kinds of living things that can exist in these areas. After a natural environment has been destroyed, it cannot be regenerated quickly, no matter how much money and technology one has at one's command. Some things simply cannot be bought. The appearance of a natural forest may be obtained by moving in large trees and planting understorey vegetation-if one has enough money. A truly natural for­ est, though, maintains its diversity in a state of dynamic equilibrium involving the canopy or overstorey tree layer, the tree understorey and shrub layers, herbaceous plants and mosses, and the small creatures and microorganisms that inhabit the soil. True restoration of such a natural for­ est, one appropriate to the site, takes at least a hundred years. Restoration of fragile plant communities, such as the raised bogs of Ozegahara in the northernmost part of Japan's Kanta Plain, for example, is close to impossible even over several hundred years if the bog surface has been eroded right down to the peat layer. The type of re-greening that has been prac­ ticed in Japan so far, namely, planting all the industrial parks, roadsides, and urban areas uniformly with grass and

NATIVE FORESTS OF NATIVE TREES

61

sparse stands of exotic trees, and counting these areas as tracts of greenery, can neither deal adequately with present environmental threats nor be called real greening. What is needed is a new type of greening appropriate to our era. NATIVE FORESTS OF NATIVE TREES

In March 1997, an international symposium on "Shinto and Ecology" was held at Harvard University. Some two hun­ dred scholars of Japan's ancient Shinto religion and of the biological sciences attended, from across the United States· and from various European countries. I delivered the key­ note address, "Bringing Chinju-no-mori to the World." In my talk I spoke of how, in contrast to monotheistic societies where people regard images of saints or church interiors as sacred, in Shinto, the symbols for the eight hundred myri­ ads of divinities are found in nature, especially in large, ancient trees and dense, luxuriant forests, which are feared, respected, and revered. When our ancestors founded a village or town, they cleared the natural forest for development but always built a small shrine to honor the village's guardian god in a forest area which they left intact. They also erected shrines where particularly impressive large trees grew, as on mountaintops, along shorelines, near springs, and so on, and they wor­ shipped the gods in these places. Japan's administrators skillfully combined the spirit of Shinto and the spirit of Bud­ dhism, which was introduced to the country about 1,200 years ago. If we liken nature to a human face, the areas comparable to the vulnerable eyes are the most sensitive spots, such as mountaintops, steep slopes and ridges, and coastal areas. It was forested areas at these sensitive spots that our ancestors set aside. There was always the chance that someone would unthinkingly wipe out these forests, however, so in order to protect them people chose them as sites for worshipping the

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mountain gods, Hachiman the war god, or the gods of the harvest, water, or sea. A belief was inculcated in the people that "If you destroy the gods' forest, you will suffer divine retribution." Thus nature's weak spots were preserved and nurtured. These forests are called chinju-no-mori, the forests where the gods dwell. A Contrast with Japan

When we take an ecological view of the world's great civi­ lizations and of the surrounding countryside, now half­ desertified, which once supported their central cities, we find that their situation contrasts with that of Japan. In Japan, a unique civilization rooted in each island and district of the archipelago arose over more than two thousand years without a single instance of catastrophic environmental destruction by humans (as opposed to frequent attacks by earthquakes, typhoons, and other natural phenomena). This success resulted from the practice of coexisting with forests and from the way people have been supported by their local forests, as symbolized by chinju-no-mori. These groves and forests not only were sacred to Shinto but also performed other functions. From an ecological point of view, they serve as forest reserves and at the same time symbolize the traditional Japanese landscape. Before the importation of Western-style city parks with their expanses of grass, shrine precincts surrounded by chinju-no-mori served as places where Japanese could relax and where they staged festivals and fairs. Most chinju-no-mori were ever­ green broadleaf forests, like those that formerly occupied most of the southern half of Japan. The main trees found in such forests are castanopsis species, laurel-family trees, ever­ green oaks, and camellia, all of which are evergreen and have taproots that go straight down to great depths. Thus they are not at all disturbed by typhoons or earthquakes and have also proven their worth as barriers against the spread of fire, as in the Kobe earthquake of 1995. The unique chir{ju-no-mori thus serve as the living framework of the

SOURCE OF THE HOMELAND IMAGE

63

local green environment and landscape, protect the lives of people dwelling around them, form the basis of Japanese culture, and are places where people's hearts are at rest. Source of the Homeland Image The chinju-no-mori where the gods dwell is the source of the image of homeland, or furusato, that remains with Japa­ nese who are born in a village but leave during their youth to go live in a city or even in another country. In the Bitchu region of western Japan, where I grew up, performances of kagura music were held from ancient times in the shrine precincts on autumn festival days, just when it started to turn quite cold. On a day near the end of November, they would last until the gray dawn of the fol­ lowing day. I remember entering the shrine precinct on such a morning and looking up at the sky. The way the almost frighteningly deep green of the surrounding chinju-no-mori grove resounded deep within me left a profound impres­ sion on my young mind; it remains with me to this day. Preservation of local forests is not limited to Japan. By about 1800, the natural beech and oak forests in Europe had been largely destroyed, leaving nothing but bare steppe in some places. The government 1 of Prussia recognized that the main causes of the destruction were forest burning and pas­ turing livestock in forests, and it issued a decree prohibiting these practices. Subsequently, other European countries also prohibited these practices and passed logging regulations mandating reforestation of an area equal to the area of natural forest being logged. Now, on the plains of such countries as Germany, the Netherlands, Belgium, Denmark, and France, one can almost invariably find strips of broadleaf oak, oak-birch, or oak­ white birch forest. Many of these forests have recovered to the extent that, at least with respect to their mix of spe­ cies, they are identical to the original vegetation of the area. This is the result of the continuous efforts of local people who are united in their determination to bring about the

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FORESTS AND CIVILIZATION

recovery and sustenance of their village forests in view of their painful past experiences, regardless of the shifting of national boundaries and the rise and fall of governments over the past two hundred years. Can such "native forests of native trees," like the chinju­ no-mori of Japan, play a role in environmental conserva­ tion? Indeed they can. In fact, our research group (based at the Japanese Center for International Studies in Ecology [JISE], originally based at Yokohama National University and receiving continuing support from that institution) is attempting to extend throughout Japan and overseas the restoration of a new generation of chinju-no-mori, with the twenty-first and twenty-second centuries firmly in mind. Chapter 5 of this book discusses those efforts, which have had success in several parts of the world. Before we try to institute plans to conserve our green environment, however, we must understand how plant communities function. This is the focus of the next three chapters.

system of potted saphngs is maintained in good condition to ensure success in trans­ planting. Above: Environmental protection groves on grounds at Oita Steelwo1*s of Nippon Steel Corporation in Oita Prefecture. Taken in 2005, the picture depicts one of the initial successes in reviving trees of native species. (Photo by Masayuki Tsutsui) Below: Oita Steelworks workers led by Profes­ sor Miyawaki examine newly planted saphngs in 1974.

Japan's Potential Natural Vegetation Map Cowberry-spruce class (alpine, subalpine areas) [I] Cowberry-creeping pine alliance [TI Yezo spruce alliance

[D Veitch's silver fir-spruce alliance [I] Erman's birch-buttercup class

Siebold beech class (Summergreen deciduous forests) [TI Basswood-mizunara oak communities and others

[]J Chishima sasa-Siebold beech alliance

[TI Suzutake sasa-Siebold beech alliance

[J[J Japanese elm alliance and Japanese wingnut alliance 9

Siebold hemlock alliance

o:2J Red pine alliance

Wild camellia class (evergreen broadleafforests)

[DJ Shirakashi oak-akagashi oak alliance [ID Japanese maesa-sudajii castanopsis alliance 13

Psychotria-sudajii castanopsis alliance

- Nagami psychotria-kusunoha evergreen maple alliance

QTI Japanese hawthorn-ubamegashi oak alliance

� '12

l2 J;!

ll fll'

J.l

q,g

12 �2

0

100

200km

Revised map from Nihon Shokusei Binran (Handbook of Japanese Vegetation), published by Shibundo in 1994; The scientific genus name is used as an English name when there is no actual English name. (Map created by Jmap)

6

Common in each class

QI] Japanese black alder class, Sakhalin willow class 17

Small cranberry-Sphagnum class (raised bog)

18

Reed class _(fens)

19

Pondweed class (submerged plant community)

[IQ] Uragiku aster class (salt marsh vegetation) [}TI Coastal Glehnia class (dune vegetation)

[m Fujiazami thistle-Hondo cam­

panula and other associations (volcanic vegetation)

·=:·f➔• ,14

·w

12

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100

200km

Omiwa Shrine at the foot of Mount Miwa in Nara Prefecture. One of the oldest shrines in Japan, its object of wor­ ship is Mount Miwa itself and the sur­ rounding forest. A chinju-no-mori (na­ tive forest of native - · �'---�·�----­ trees] in a rice field in Oita Prefecture.

Japanese blue oak

shirakashi oak

sudajii

castanopsis

tabunoki laurel

Left: Soil-covered hillside banks where lawn grass grew near main entrance of Yokohama National University in 1978. Right: Native species saplings planted within width of 1 to 1.5 meter on the same forty-degree slope.

Above: Saplings reach a height of four meters three years after planting. Shrubs which thrive in forest margin were planted in space between the open road and future grove. This was designed to keep the fallen leaves in the narrow strip of the grove. Below: Photo taken in 2006. The grove had become stable after some ten years and continues to flourish.

In 1998 Chinese citizens and Japanese volunteers planted Mongolian oak saplings around the Great Wall of China. Right: Professor Miyawaki inspected the area during the previous year. Near Belem, Brazil, local citizens including chil­ dren planted saplings to restore a lowland tropical rainforest in 1995.

After 14 years of planting saplings of the native species of dipterocarp trees in 1991 on the norihern coast of Borneo. the Malaysian University of Agriculture succeeded in creating new tropical rainforest. An environmental protection grove planted in 1982 along the Kashihara Bypass near Yamatotakada flourishes after ten years and functions as a filter of dust and noise ji·om the road traffic.

Figure 6. Climatic Potential Biomass Accumulation on the World's Land Areas

The potential maximum amount of plant biomass that can accnmu­ late at a site, assuming that nutrients and other factors are not limit­ ing, is determined indirectly by climate, through its effects on the rates of production (photosynthesis) and maintenance costs (respiration) of the vegetation. These climate-driven processes were simulated using climate data, for each site (pixel) on the map, permitting the vegeta­ tion to "grow" until it reached equilibrium with the local climate. This happens because photosynthesis reaches its maximum relatively early in succession, but respiratory losses continue to increase as the amount of biomass to be maintained increases. The resulting poten­ tial maximum biomass, at equilibrium, is shown on the map and rep­ resents an upper bound on the amount of carbon that could ever pos­ sibly be sequestered in terrestrial vegetation-if the land were abandoned and allowed to grow up to its maximum potential. Biomass levels on the map (in kilograms of dry biomass), and the land­ scape they generally represent, are as follow: brown O kg (deserts with no vegetation) light brown 0-1 kg (semi-deserts, tundra) yellow 1-5 kg (grasslands, shrublands) 5-10 kg lightest green (scrub/open woodlands)

medium green (woodlands) dark green (closed forests) medium blue (tall rainforests) dark blue (tallest rainforests)

Polar and high-mountain icecaps are shown in white.

10-30 kg 30-70 kg 70-80 kg >80 kg

Chapter 2 Communities of Living Things

Biological Communities Living organisms are not governed solely by external physi­ cal conditions. They also coexist with each other, interact­ ing and sharing each other's fate. This coexistence is an essential condition for the evolution of species and genera; even the relationships between predators and their prey must be maintained in a dynamic equilibrium. Creatures interact with the physical environment through a division of labor: some creatures are producers (green plants), some are consumers (herbivores and carnivores), and others are decomposers. Taken together, all these inter­ actions create a system of material and functional balance­ the ecosystem. From a social point of view, living beings, both individually and as species, compete with and tolerate one another, coexisting by managing within their limited living space. We call such a group of associated organisms a biological community. A biological community is neither an instinctive, orderly assembly with a division of labor, such as a beehive or an anthill, nor a mere collection of individuals. It is a group of organisms living together in a certain environment, maintaining a dynamic balance through direct and indirect relations between individuals and effecting changes in the living environment. It was Karl Mobius, in the later 1800s, who coined the term biological community. A more formal 65

66

COMMUNITIES OF LIVING THINGS

definition for such an assemblage is: a community con­ taining types and numbers of species and individuals inter­ acting under uniform external conditions and persisting sustainably in a given area by breeding. That is to say, a biological community is a group of living organisms in a given location. It is a living system of plants and animals ' interacting and maintaining a dynamic balance under the given environmental conditions. Kerner von Marilaun, writing in 1863, noted that the divi­ sions and groupings in a biological community, which are created by the associations among species, are by no means coincidental. Though superficially they may appear unregµ­ lated, they are in fact systematic. All creatures have their particular places, t_ime, and functions in the community. The variety of species in a biological community is called biodiversity, a term that encompasses both the number of species (species richness) and some aspects of the relative abundance of the different species. A more comprehensive concept of biological diversity is that of biocqmplexity, which includes diversity not only in entities but also in the many functional relationships just suggested. In biological communities, relationships among individ­ ual creatures and among species are diverse. The simplest type of communal life involves creatures living under the same environmental conditions. The minimum requirements of space, water, nutrients, and other necessities for each liv­ ing thing are fixed quantities. In order to coexist anywhere, each inhabitant must engage in various levels of competi­ tion for its survival. No one creature monopolizes the avail­ able space and energy; rather, these resources are shared. Thus, within the biological community, the habitats of the member populations are segregated, horizontally and verti­ cally, according to each group's mode of life. For example, a forest consists of an overstorey tree layer, perhaps an understorey tree layer, a shrub layer, a ground layer of herbaceous plants, possibly a layer of mosses or lichens directly on the ground, and certainly an underground sys­ tem of roots. All these components, above and below

BALANCE IN NATURAL COMMUNITIES

67

ground, divide the living space three-dimensionally and coexist while competing with one another. To a certain extent, a biological community can restore a destroyed portion of itself by re-forming its living environ­ ment anew or by relocating itself. If animal species emigrate, however, or if plant or animal species become locally extinct, the biological community usually cannot restore the origi­ nal species structure by itself. Under extreme environmen­ tal conditions the structure of the biological community may gradually erode. Under balanced, varied environmen­ tal conditions, though, it may become richer. In many cases we cannot determine, in the course of these changes, the precise moment when one biological community turns into another. A biological community does not have precise bor­ ders in space or time. Balance in Natural Communities

In the absence of environmental degradation or destruction caused by internal or external factors, the collection of species that forms the structure of a biological community normally does not change, even though individuals come and go. This can be seen, for example, in a natural forest or natural grassland. Even if certain environmental conditions do change somewhat, as long as the basic conditions remain the same, the biological community retains the same struc­ ture and structural relationships. This phenomenon has been termed the balance of the biological community. One thing that is clear about the balance of a biological community in nature is that, when one part of a community is destroyed, the community restores the balance by altering reproduction rates or patterns. It has been reported that, even in human societies, when population has fallen dramatically or when the ratio of males to females has become imbal­ anced due to war or other causes, birthrates and the propor­ tion of male births increase. Among plants and animals this phenomenon is even more pronounced. In most plant and many animal species, one individual produces thousands or

68

COMMUNITIES OF LIVING THINGS

millions of seeds or offspring. In an intact biological com­ munity, however, only a very few individuals avoid death at the hands of physical stresses or biotic factors (such as being eaten). In most cases these few individuals represent the number needed to maintain the structure of the biological community. For example, in the natural pine forests of Eu­ rope, the pine caterpillar coexists as a small part of the pine­ forest biological community. In a monoculture of pines, how­ ever, where other tall trees and shrubs have been cut down, the natural balance of a multi-layered plant community has been destroyed, and under certain climatic conditions the caterpillar population increases explosively, inflicting dam­ age so extensive that it can wipe out whole plantations. Humankind is presently experiencing an unprecedented level of rapid population growth. Is this not a biological phe­ nomenon reflecting the loss of harmony between human beings and nature? If this is the case, we cannot be unre­ servedly happy about the brilliant progress of civilization. Will humankind have to face severe retribution from nature in the near future, as nature starts to restore the community balance that has been destroyed by our rapid increase? The condition of balance is a result of the overall com­ bined effects of the innumerable actions and reactions that occur within an ecosystem. The well-known German animal ecologist Karl Friederichs felt that this balance was connected ultimately with global and cosmic phenomena, so he spoke of a more general whole-system balance (holozonotisches Gleichgewicht) in ecosystems. Continued human develop­ ment and future prosperity can be guaranteed only within such ecological balance. Like the origin _of life itself, the rea­ son for this whole-system balance-what holds it together, how the relationships are structured-remains an unsolved mystery even today. Actual and Abstract Plant Communities All forms of life are members of a biological community. The total of all the plants that cover a specific area is called

EXTERNAL CONSTRAINTS ON PLANT COMMUNITIES

69

vegetation. When vegetation is conceived as a unit, it can be called a plant community, a term that normally also implies a particular assemblage of plant species that exists under given environmental conditions. The different patches one sees when looking out over a landscape, especially a fragmented, human-modified, landscape, represent different plant communities. The term is used to identify actual liv­ ing communities, for example the Japanese larch commu­ nity at Oniwa ("The Garden") on the slope of Mount Fuji, the kobomugi sedge (Carex kobomugi) community found on the sandy beaches at Chigasaki on the Pacific coast of Japan, or even a stand of roadside weeds at a particular place. The term plant community may also, however, refer to an abstract grouping of plants or plant species that may exist under certain conditions. For example, when we speak of weed communities in agricultural fields or roadside wild­ plantain communities, we are not referring to actual com­ munities or sites but rather to plant communities that occur under such conditions in general. In these examples, the communities are surviving in environments continuously subjected to severe, ongoing human intervention, in agri­ cultural fields that are cultivated, fertilized, and weeded without rest for long periods, or along roads that are con­ stantly in use. EXTERNAL CONSTRAINTS ON PLANT COMMUNITIES

From the dry interiors of the continents to the depths of the oceans, human beings have made an exhaustive study of the planet and so far have found no place on earth utterly devoid of life. From the most benign environments to inhospitable high altitudes and deserts, life in one form or another car­ ries on with cooperative ways of living adapted to the envi­ ronment at hand, in dense aggregations or sparsely spread out over great distances. Vegetation exists in a great variety of structures. These range from complex multi-layered communities in the most

Figure 7. Physiological and realized niches physiological optimum

ecological optimum

A ecological optimum

C

B

ecological· optimum

ecological optimum

D

A niche, in the ecological sense, represents the environmental space or habitat in which an organism can live. Here, environmental space is represented horizontally and the organism's biological response, in terms of fitness and perhaps abundance of occurrence, is shown vertically. The physiological niche of an organism, shown as the hemispheric shading, represents the physiological tolerance limits and correspon­ ding potential abundance of the organism. In some areas where the organism could live, however, it is outcompeted by other species. The realized niche, shown by the differently shaped shaded areas, repre­ sents the organism's resulting actual habitat. With no competition from other species, the organism may be able to occupy its entire physiolog­ ical niche (A). With competition, however, the realized niche changes. It may be skewed to one side (B), as with savanna grasses that have especially high optimum growth temperatures (the horizontal axis rep­ resents temperature). Under other conditions, the realized niche may be narrowed (C) toward the organism's physiological optimum, where it can outcompete other organisms; and the organism is absent from peripheral areas, where it is in turn outcompeted. Finally, some gener­ ally less competitive species, such as larch trees, may be constrained to live only near their physiological limits (D), where other species per­ form even worse or are absent entirely..

EXTERNAL CONSTRAINTS ON PLANT COMMUNITIES

71

favorable environments, such as tropical rainforests (with multiple tree layers, various shrubs, and herbaceous plants), to simple, low-growing communities in extreme environ­ ments, such as desert dwarf-scrub, grassy tundra, or ground covers of small wildflowers only ten centimeters high. The most extreme environments support only one-layer commu­ nities that may be composed of a single species, such as the communities of kobomugi sedge that grow on eternally shift­ ing seaside dunes or the communities of glasswort (Suaeda maritima) that grow in the salt marshes of estuaries and other areas periodically flooded by seawater. In this way, each unique community of living things pursues its particu­ lar way of life in exact accordance with even the slightest differences in local conditions. In nature, plants and animals seem to be living in ideal environments. Plants by a stream or pond love the water. Plants in sunny spots love the sun, all blooming beautifully. The birds and insects all live in their most favored places, raising songs in praise of spring. In reality, however, a strict system of competition and endurance governs communities of plants and animals. It is especially in the world of plants, which lack the ability to change their locations, that the most severe competition for survival occurs. And most plant species have to germinate, grow, flower, and endure in a habitat different from the one to which they are best suited. Each plant expends its energy on survival, but the great majority of them fail to survive because of external conditions-the physical environment-or because of regu­ lation internal to their communities. Those plants that remain form the unique local community. Even the commu­ nities of roadside weeds or the components of the grass com­ munities in our yards are just managing to survive. Because they cannot move, plant communities must use every bit of their energy for survival-competing, enduring, and striv­ ing to persist by adjusting their particular ways of life as much as possible to the given environment, while at the same time coexisting with other species.

External Limitations

To become a member of a plant community, every individ­ ual plant has to overcome at least two barriers. The first is the community's environmental, or external, constraints. The second is internal regulation within the community. Try this experiment in your own garden or a vacant lot. Level the ground so that not a plant is left standing. Within two weeks, assuming that it is not winter, you will find weeds sprouting all over the site. To find out exactly how many plants would sprout in an area of one square meter, we once attempted such an experiment on the grounds of Yokohama National University. On an area that had been stripped of grass in early August and was completely bare, we counted the number of weeds that had appeared after one month. A square-meter test plot was divided with string into a hundred smaller test plots 10 centimeters on a side, and the plants that grew up in each square were carefully counted. The results showed that, in all, 17,776 plants had sprouted in the one-meter-square test plot-which was a great many more than we had expected. The number of seeds in the ground on an area of comparable size, how­ ever, may number in the hundreds of thousands or even more than a million, as in the store of seeds, called the seed bank, that is buried in reserve in lawns, fields, and vacant lots. In light of these enormous numbers, the figure of 17,776 plants sprouting in the square-meter plot is none too high. In fact, considering the total number of seeds lying dormant in the ground as well as seeds blown to the site from neighboring areas, this number seems too small. The list of plants living near the plot (the flora) included a thou­ sand species. All of them could have sprouted in the exper­ imental plot. In reality, however, only some 30 species were found. This raises the question of why the other 970 species were not there. Most of them failed to sprout at that particular time because they could not adjust themselves to the first constraint on plant communities: environmental conditions.

EXTERNAL LIMITATIO NS

73

Three main classes of environmental factors control the constitution of plant communities: • Climatic factors: sunlight, temperature, humidity and precipitation, and wind, as well as variations such as the distribution of precipitation throughout the year, the consequent wet and dry seasons, and the variability or reliability of all of these factors from year to year. • Soil conditions: physical properties, such as the size of solid soil particles, the mix of coarse and fine particles, and the resulting soil porosity and water-holding capac­ ity; and chemical properties, such as soil pH and fertil­ ity, which are determined primarily by the quality and quantity of inorganic and organic nutrients, mainly compounds involving- nitrogen, phosphorus, and vari­ ous minerals such as calcium and potassium. • Disturbance regimes: the types, intensities, and dura­ tions of both natural disturbances, such as fires or storms, and the uses of the soil, plant species, or whole plant community by humans or other animals. Of the various environmental factors that we can analyze and quantify, very few have a unilateral and independent effect on the lives of plants, animals, and their communities. Plants grow and animals emerge in the context of a unified dynamic, in which the presence or absence of any one par­ ticular factor is to a certain extent compensated by other factors. For the sake of research, we can further separate the impor­ tant effects of these environmental factors. Take tempera­ ture as an example. Temperature differs at the surface and underground, at various heights and depths, and it changes seasonally and during the day. Similarly, several aspects of precipitation and other water availability can also be identified. Does the precipitation come in the form of rain, snow, fog, or dew? How much, in what seasons, and at what times of day? How much is absorbed by the soil? How is the water distributed in the soil, according to the type of soil

74

COMMUNITIES OF LIVING THINGS

and its density? The more such things are investigated, the more detailed are the measurements and analyses required. The various environmental factors do not act separately, of course, but in relation to one another in their effect on the existence and growth of living things. When a certain factor is inadequate, other factors can compensate to a cer­ tain extent. For example, a supply of water and the soil's ability to absorb it are environmental conditions required for the growth of plants. These factors depend, however, on the interplay of other environmental factors, such as temperature, light, wind speed, and the physical and chemical properties of the soil. With high temperatures, strong winds, and direct sunlight, more moisture evaporates from the soil or tran­ spires from the plants themselves than under the conditions of low temperature, light winds, and shade. Unless there is more precipitation or other available water, plants will not be able to survive under the warmer or windier conditions. A place where there is shade, fine-grained soil, and protec­ tion from the wind may be able to compensate to a certain degree for insufficient precipitation or other water supply. When a diverse natural environment provides sufficient water, sunlight, and nutrients, complex forests emerge. If natural conditions or human intervention cause just one out of many environmental factors to be too scarce or too abundant, the biological community breaks down. When this happens, the first to succumb are the most competitive plants, those of the overstorey tree layer. The next to go are those in the understorey tree layer, then the shrub layer. Eventually plant life is reduced to very simple communities such as the grasses of lawns and golf courses, or the plan:.. tains that grow along paths. In the natural world, single-layer plant communities are often found in harsh environments, such as the coastal kobomugi sedges already mentioned, sphagnum moss in bogs and marshes, or communities of small alpin� plants above the tree line in high mountains. These simple com­ munities consisting of uniform stands of only a few species are extremely vulnerable and can be very unstable. They

INTERNAL REGULATION IN PLANT COMMUNITIES

75

are quite sensitive to even small changes in the natural environment and to slight human intervention, which can degrade them or cause them to disappear completely. The synthesized balance of environmental factors (includ­ ing even the slightest human intervention) creates plant communities unique to their particular localities. When envi­ ronmental conditions are diverse and balanced, complex communities form, with many animals and plants of vari­ ous sizes. This situation is perhaps best exemplified by the environments of tropical rainforests, where high tempera­ tures and high humidity prevail year-round. Tropical rain­ forest communities have overstorey and understorey tree layers, a shrub layer, a herbaceous plant layer, and a moss layer, with about forty to fifty species per hundred square meters, or up to sixty or more in particularly rich areas. Natu­ ral forests harbor a great diversity of anima}s and plant com­ munities, with their variety arranged both vertically and horizontally. They are the strongest manifestation of nature. INTERNAL REGULATION IN PLANT COMMUNITIES

Let us return to the experiment with weeds growing in a square meter of bare ground. We began this experiment one September, and a month later the plot was covered with 17,776 weed shoots, many involving species of the chrysan­ themum family. This huge number of plants survived the severe winter that followed by hugging the ground, either creeping along it or forming rosettes of leaves that radiated out from a center but stayed close to the ground. In the warmth of spring, every plant suddenly sent up shoots toward the sky, with some plants, such as the weedy annual fleabane (Erigeron sumatrensis, also recently called Conyza sumatrensis), growing as tall as one meter or more. With the coming of summer, each plant species began to flower in turn. By the end of the summer each species that had germinated the previous September had completed one life cycle, having grown up, flowered, borne fruit, and produced

76

COMMUNITIES OF LIVING THINGS

seeds for the next generation. The fleabane, for example, produced between 70,000 and 700,000 seeds per individ­ ual. Of the 17,776 shoots counted originally, however, only 76 grew to full size and produced seed. In just ten months, the original number had drastically declined. Why did the other 17,700 not survive and grow to full size? Every crea­ ture, as soon as it is born, immediately faces not only the external conditions of its environment but also interference from other species and from individuals of its own species. Thus, each creature can survive only if it manages success­ fully according to the internal regulation, or social regula­ tion, of the community. Internal regulation in plant communities can be roughly divided into three categories: competition for space, nutri­ ents, and energy; harmonious coexistence; and endurance. Competition. The best-known social relationship among creatures in biological communities is competition. To sur­ vive, all creatures-insects, plants, humans, and other ani­ mals-require a minimum of space, nutrients, and energy (the minimum differs according to the species, of course). As each creature grows, its needs for space and energy also increase, and the competition between individuals and between species intensifies. IJ two plant species need exactly the same resources and compete too directly for them, one species will usually be stronger and win, elimi­ nating the other. In ecology this is called competitive exclu­ sion and can reduce the diversity of a community. Usually, however, both plant and animal species find ways of com­ peting less directly. Two types of competition can be recognized within plant communities: direct and indirect. In direct competition, each plant tries to grow faster than its neighbors and be the first to occupy space, thus acquiring more light, water, nutrients, and so on for its own exclusive use. Direct com­ petition can also be of two types. In the first type, the first plant species to sprout in barren ground comes to dominate the area temporarily. Later species have only three options:

INTERNAL REGULATION IN PLANT COMMUNITIES

77

supplant the existing species, accept its dominance, or die out. Normally it is very difficult for plant species following the same mode of existence to supplant a predominant spe­ cies that is already established. Many plants accept domi­ nance to the limit of their endurance and eventually die out. The second kind of direct competition occurs in natu­ ral forests that have multiple plant layers. A tree seedling germinating in the shady understorey environment cannot immediately grow up into the canopy. It can only grow at its normal rate and survive as best it can to have a good chance of taking its place in the next generation of primary canopy occupants. As long as the existing large trees remain, most of the younger and smaller trees will either stay as they are until the tall trees die, or die if they cannot endure. In indirect competition, one species tries to limit or pre­ clude the growth of others by causing changes in the imme­ diate habitat, for example by acidifying the site through accumulation of raw humus or, in some species, by excret­ ing toxic substances. The Japanese larch offers an example of indirect competition. When the larch is planted on unsuitable soils in forests, it is difficult for the bacteria and tiny organisms living in the soil to decompose the fallen needles that accumulate on the forest floor. As a result, acidic raw humus that is only half-decomposed accumu­ lates in the topsoil. Normally, topsoil consists of a mixture of particles derived from the breakup of minerals together with organic matter originating from both plant and animal sources, which has been decomposed and reduced by soil­ dwelling organisms. Topsoil is thus full of life. When mat­ ter accumulates that cannot be decomposed, however, such as larch needles, the seeds of other plants cannot grow. This is indirect competition, a situation in which the envi­ ronment is altered to prevent the growth of other plants. In human societies, even if the competition is fierce, with direct competition one at least knows who the competitor is; the causes and terms of the competition are also clear, meaning that one knows what to do. Indirect competition and indirect attacks are more formidable. Exactly how and

78

COMMUNITIES OF LIVING THINGS

by whom one is being assaulted is unclear. By the time one realizes what is going on, the environment has deteriorated to such an extent that one is forced to surrender it to some other social group or individual. In a biological community as well, the most fearsome factors are the unquantifiable, indi­ rect ones-in other words, environmental change. It is these indirect assailants, such as pollution, pesticides, germicides, herbicides and food additives, that are slowly invading our living environment and causing environmental changes for which we should be most carefully on the lookout. Harmonious coexistence. Human society often holds up har­ mony as an ideal, so it is easy to jump to the conclusion that the concept of harmonious coexistence is an achieve­ ment of human intelligence. But harmonious coexistence is by no means unique to human society: it is the primary req­ uisite of any biological community. Within an ecosystem, competition is merely one facet of harmonious coexistel)-Ce. According to experiments on growth and competition among such plants as the komatsuna rape (Brassica rapa var. parvidiris), conducted in the 1960s by then-professor Tatsuo Kira of Osaka City University, infant seedlings grow better, to a certain extent, when planted densely. Japanese farmers' practice of planting five or six seeds of Chinese cabbage or Japanese white radish per hole is perhaps based not simply on the assumption that at least one seed will sprout but also on the traditional knowledge that several seeds sprouting together grow better than one by itself. The harmonious coexistence of plant species takes vari­ ous forms. Competition is fiercest between species with similar capacities or the same mode of life. Among species with dissimilar modes of life, however, phenomena that may appear superficially to be evidence of competition usu­ ally turn out, when viewed comprehensively, to be evi­ dence of harmonious coexistence. For example, in forests just inland from Japan's Kanta region (the plain around the Tokyo-Yokohama area), evergreen (laurophyll) broadleaf

INTERNAL REGULATION IN PLANT COMMUNITIES

79

trees such as sudajii castanopsis ( Castanopsis cuspidata var. sieboldii) and tabunoki laurel (Persea tlmnbergii) make up the overstorey tree layer. (Many Asian species have no Eng­ lish name, even some important large trees, so we will use the genus name or Japanese name, sometimes both, as is done in horticulture.) Similarly, in more inland evergreen broadleaf forests, castanopsis and evergreen oaks, plus tabu­ noki laurel, make up the overstorey tree layer. The remain­ ing space, using the small amounts of sunlight that penetrate the overstorey, is occupied by the following plants: ever­ green shrubs such as spotted aucuba (Aucuba japonica), Japa­ nese fatsia (Fatsia japonica), shirodamo neolitsea (Neolitsea sericea), Japanese privet (Ligustrum japonicum), and hisakaki (Eurya japonica); evergreen herbaceous plants growing on the forest floor, such as monkey grass (Liriope graminifolia), dwarf lily-turf (Ophiopogon japonicus), and Reineckia lily (Reineckia carnea); and evergreen fern species such as beaded wood fern (Dryopteris bissetiana) and Korean tas­ selfern (Polystichum polyblepharum). These plants must compete hard for the water and inorganic nutrients they need for growth. They coexist in harmony with the overstorey trees, however, through habitat segregation (see p. 82), together forming a plant community. If the overstorey cas­ tanopsis or evergreen oak trees are cut down, sunlight and wind suddenly penetrate to the shrubs and herbaceous plants, retarding their growth and ultimately endangering their existence, too. Prehistoric Europeans pastured livestock in forests, where the animals ate shrubs, tree seedlings, and herbaceous plants, leading to deforestation. Loss of the over­ storey trees devastates a forest. Destruction of the shrub layer and herbaceous plants through livestock pasturing, harvest of understorey vegetation, or removal of leaf litter can also destroy a forest. All these human interventions wreck the harmonious coexistence in a forest and, eventu­ ally, the forest itself. In nature, even adversarial relationships, such as that of predator and prey, or of parasite and host, are based partly

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on a delicately harmonized coexistence. According to Konrad Zacharias Lorenz (1903-1989), whose lifelong study of animal behavior won him a Nobel Prize, it is the predator in a predator-prey relationship that is more vulnerable. Con- 1 sider a predator-prey system involving snakes and frogs. The snake preys on the frog for food, but if the frog popula­ tion shrinks by 90 percent, the snake no longer has enough to eat, and the snake population shrinks drastically. Then the number of frogs increases again, followed by the num­ ber of snakes. In the long history of life on earth, there have never been enough snakes to eat all the frogs. Lorenz showed, however, that if one of these species died out, it would be the snake, despite its aggressiveness. The delicate coexistence of the snake and the frog is char­ acteristic of a biological community. In a similar way, human beings are parasites on the plant world, and only as such can we realize our full potential. The word parasite sounds unpleasant, but it was not originally pejorative. The parasite sucks the blood of the host, bl.l-t if the host weak­ ens, the parasite relents until the host recovers. Then it sucks anew, but not constantly. If it sucked the host dry, the parasite would also die. We humans, as parasites on the plants that are essential to our existence, must take care not to suck our hosts dry. Endurance. No individual in a biological community, not even a dominant one, can live as it wishes. Every creature is forced, to a greater or lesser extent, to endure as a mem­ ber of its community. It is in plant communities that this kind of endurance is most rigidly demanded. In laboratory conditions and in monoculture afforestations, the plants that grow best are those that occupy the best places, those loca­ tions where all conditions are most favorable for the plant's growth. In nature, however, the better the conditions, the more numerous the competitors. Thus most plants gener­ ally coexist with other plants in areas where conditions are slightly less than physically ideal. Yet species living in

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slightly adverse conditions are stronger in a biological sense: they are adaptable enough to cope with a certain level of natural adversity or human disturbance. No member of a plant community has the power of loco­ motion. The place where an individual sprouts is where it stays, regardless of whether the space is already occupied by another plant. The individual is simply obliged to wait and endure until the plants above die and fall down. If it cannot wait and endure, it dies. In a forest there are nor­ mally young trees with the potential to grow and become the next generation in the overstorey. Their growth is impeded at first by the shade cast by the full-grown trees, and they must wait patiently in the understorey for the overstorey trees to die. In human soctety, if one can wait for twenty to thirty years at the very most, a new generation will have taken over. If one cannot wait, he or she can move to another organization or to some other place, where another social system prevails. In a plant community, only those plants that can wait patiently for dozens or, in some cases, even hundreds of years can hope to become part of the next gen­ eration in the overstorey. Whether in wilderness covered with natural forest, in grassland, in agricultural fields or pastures created by humans, or in weed communities in vacant lots, plants can­ not grow freely. Those plants that have been able to endure all the severe environmental conditions and have managed to sprout then face stiff competition from the other individ­ uals and groups of plants in the area. Most plants have to endure life in a place that is a little too dry, or a little too wet, or in some other way less than ideal. In a more favor­ able environment, one that is warm, has just enough mois­ ture, and has deep soil rich in nutrients, the number of species and individuals that have the potential to thrive increases, encouraging stronger competition. Thus, those plants living in favorable physical conditions are also forced to live in a place that is less than ideal. This princi­ ple applies also to relations between plant communities.

Habitat Segregation We can see that plant communities, which appear to be para­ gons of peace-, actually involve the most severe competition among individual plants. Plants coexist harmoniously in communities only by enduring each other and segregating their habitats, in both space and time. This mode of life can be observed in forests, in the relations between overstorey trees and shrubs or herbaceous plants, and in fields, in the relations between summer weed communities and those that live there from winter to spring. The harsh dynamics of social interference between individuals and species are manifested in the distribution of plant communities in our gardens and in the wild. Let us take a walk in a natural forest in Japan. On the Kanta Plain, most of the area below seven hundred meters in altitude was once covered by evergreen broadleaf laurel forest. In nearby coastal regions the largest trees in the for­ est are sudajii castanopsis and tabunoki laurel. Inland, the largest trees are various castanopsis species, laurel-family trees such as tabunoki, and evergreen oaks (kashi or gashi in Japanese) such as shirakashi oak (Quercus myrsinaefolia), Japanese blue oak (Quercus glauca), and urajirogashi oak (Quercus salicina). Superficially, these forests may appear to consist only of tabunoki, castanopsis, and evergreen oak trees. Plant surveys in natural forests like these, however, can distinguish overstorey and understorey tree layers, a shrub layer, a herbaceous plant layer, and sometimes a moss layer. At each level, plants of various species and sizes both com­ pete with one another and coexist in a marvelous way, arranged vertically in a limited space. Having made field studies of the flora of the Japanese archipelago and of more than thirty other countries, from Siberian coniferous forests around Lake Baikal to the fifty­ meter-tall tropical rainforests in equatorial Borneo, we have observed that natural forests are arranged in a certain hori­ zontal order as well. We have seen that they do not grow

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83

right to the edges of open spaces such as meadows, rivers, lakes, roads, or lawns. An area of shrubs or vines, which vegetation ecologists call a mantle (or mantle community), always grows between the edge of a forest and the open space. This mantle (or forest-margin community, as it is also called) consists of shrub or vine species that like direct sunlight or only partial shade. They form a kind of skirt around the tall trees of the forest. Between this shrubby mantle and the open ground around it is another plant community, like a design on the hem of a skirt. This edge community, called the herbaceous fringe, is composed entirely of herbaceous plants, extends outward from the lower strata of the mantle, and may involve plants such as hedge parsley (Torilis spp.) or bedstraw ( Galium spp.). These forest-margin communities, which appear to impede the forest, actually protect it from the dry­ ness of the outside environment. Natural forests thus harbor a great diversity of animals and plant communities whose variety is arranged both ver­ tically and horizontally. Such forests are the strongest mani­ festation of nature, with a dynamic equilibrium that involves many plants and animals. They are also so strong that they can resist damage from typhoons, heavy rains, and other natural disasters. In the experimental square-meter plot described earlier, it was the extremely harsh competition within the commu­ nity itself that resulted in only 76 out of 17,776 plants growing to full size and bearing seed within ten months. The majority tried to survive and adapted their way of life and growth as much as possible, but they could not endure and so they died. After ten. months we also found about 30 individuals of creeping plants in the plot, including spotted sandmat (Chamaesyce maculata), a carpet-weed (Mollugo pentaphylla), and vines such as morning-glory (Convolvulus). These had grown underneath the individuals of the flea­ bane community, which had reached full size and borne seed. We also found about 10 fleabane individuals that had

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not grown to their full, meter-plus height but were just barely hanging on at about thirty centimeters, thin and with almost no leaves or seeds, but still alive. Normally the growth of a new plant community on land cleared of vegetation initially follows the pattern observed in our experimental plot. The plants that succeed in occu­ pying such areas are those that manage to sprout as little as one day sooner than the others and occupy the area first. Although individuals of the same species all have the same growth pattern, those that can become larger even a little bit sooner than the others can thereafter push their advantage and accelerate their growth, in the end occupying the space. The individuals that have been late to sprout find the light and nutrients already taken and thus cannot grow. The gap between the two groups widens, and the plants that sprouted first remain, while the others are forced to adapt their growth for survival on the remnants of light and nutrients left by the more successful plants. If they cannot endure these strict conditions, they are forced to wither and die. Regulation: Summary

Because plants cannot move, they possess much greater powers of endurance than humans or other animals. There is, however, a limit to how much they can adapt their mode of �ife. In particular, large trees such as castanopsis, ever­ green oak, tabunoki laurel, and beech, which always prevail in competition with other plants when environmental con­ ditions are favorable, rapidly lose their survival potential when conditions change even slightly, giving up their space to other species and communities. Generally, those plants that are good competitors require the best environmental conditions; they do not have strong powers of adaptation and cannot change their way of life in order to survive. Therefore, among individuals with the same potential, even when a great number of seeds germinate in a limited space and cover the whole surface, competition causes a natural

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selection, so that not all will die. In plant communities, every weed and tree by the side of a road is the one that endured and survived severe environmental and intra-community limitations and constraints. We have explained internal constraints by using concepts of competition, harmonious coexistence, endurance, and habitat segregation. In reality, these processes are not sepa­ rate but rather interact with each other. Competition is but one facet of coexistence; habitat segregation and endurance are required to facilitate coexistence; and so on. Thus, when investigating the dynamics of a biological community, it is risky to overemphasize any one aspect, though we may define it separately for convenience. What is needed is a holistic view that takes into account all aspects of the system. In nature's diversity, all kinds of actions and reactions are knitted together. The more that industries, cities, and civi­ lizations develop, the more diligently must we humans seek to achieve harmony between diverse environmental constraints and our social order, if we are to survive as one member of a biological community.

COMMUNITY DYNAMICS AND PLANT STRATEGIES

Optimal Locations May Not Be Optimal

The difference between physiologically optimal and ecolog­ ically optimal locations for plants was confirmed and illus­ trated in 1951-56 by Heinz Ellenberg in Germany. At first he agreed with the textbooks of the day that plants in nature lived in locations that were physiologically optimal for their growth. In Germany, wavy hairgrass (Deschampsia flexuosa) (which in Japan lives on high volcanic plains) was thought to be an indicator of dry conditions because it grew in places such as barren rocky areas or mountain ridges. When Ellenberg traveled to Poland after World War II, however, he found the same plant growing in the acidic soil of wetlands.

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In Poland, wavy hai'rgrass was considered to be an indicator plant for wetlands, the opposite of how it was viewed in Germany! To investigate this apparent paradox, he and Helmut Lieth compared monoculture and mixed plantations of various weeds and grasses in an array of experimental environments. They found that, in monoculture without com­ petitors, many of the plants grew best where conditions were most favorable. In the wild, however, where there were competitors, the same plants were forced to grow outside the areas with optimal conditions. In some extreme cases, they grew in places where conditions were most unfavor­ able. This difference between physiological and realized (ecological) habitats, or which is illustrated in figure 7. In one of the experiments performed by Ellenberg and Lieth, four species of grass occurring widely throughout central Europe were planted separately on a slope in areas of varying soil moisture content: wet, moist, and dry. Each species showed maximum growth in the (intermediate) moist location. Combinations of the four species were also planted under the same varying conditions. Only two species, false oat (Arrhenatherum elatius) and cock's-foot (Dactylis glomerata), showed maximum growth in the moderately moist location, where they grew best when planted sepa­ rately. Shortawn foxtail (Alopecurus aequalis) showed max­ imum growth in the wettest area, and Japanese brome (Bromus japonicus) in the driest. That is, only two species could grow in the place that was shown in the monoculture experiment to be physiologically optimal. The other two species were forced to grow in locations wetter or drier than their physiological optimum. Indeed, surveys of the growth of grasses in Europe show that Japanese brome grows well in dry areas, such as on mountain ridges and on limestone cliffs from the Jurassic period, while foxtail is widespread in wet fields. These findings also suggest another, less well-documented aspect of competition. We have already seen that direct com­ petition among species may lead to elimination of appar-

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ently weaker species. This may not be the result, however, if the conditions of competition are changed. For example, two plant species may compete directly in an open environ­ ment, with one eliminating the other. The same two species would encounter different competitive conditions under a forest canopy, however, and perhaps neither species could grow luxuriantly enough to displace the other. Plants and Humans Are More Than Just Similar To botanists, it appears that plant and human communities are not merely analogous or similar but actually the same in many of their attributes, including those of competition, endurance, and coexistence. If we correctly understand the fundamentals of plant communities, then we also have insight into communities of animals and of human beings. Take, for instance, the just-mentioned phenomenon of dif­ ferent conditions changing the nature of competition. In a sense, the same rule may hold in human societies, where rampant competition may be essentially out of control unless there is some more powerful authority, some "strongman" that can control or suppress the competition. These interactions within biological communities also help answer the question of why plants may not survive even when they seem to have all they need-like people who have everything they want in the way of status, money, and sex. It can be seen from the extinction of the dinosaurs that the most favorable conditions, in which every adver­ sary is overcome and every desire is satisfied, may actually not be sufficient for survival. A multi-layered plant commu­ nity, though it is less than physically ideal and may even be harsh and require considerable endurance by its members, is nevertheless a biologically ideal environment that guar­ antees wholesome survival. In such an environment, plants compete, endure, and coexist by segregating their habitats. In fact, complex forests that have several plant strata are the most stable plant communities on earth.

Dead Centers Some organisms may live in concentrated masses, due to their remarkable breeding or extremely luxuriant growth. When such a group becomes overcrowded, some individu­ als start to die off. In the case of plants, those individuals at the center often die off first and only those nearer the periph­ ery survive. One can also see this pattern of the "dead cen­ ter" in the outward growth of some individual plants, such as· rosemary and other shrubs, or in aloes and cycads with spiral (rosette) growth patterns. Temporary overcrowding in cities, environmental pollu­ tion from industrial and chemical production, the bull­ dozing into uniformity of diverse topographies and living communities, and the destruction of green environments should not be permitted to threaten the survival of the human species over the long term. In the grip of a predator, the lizard sheds the end of its tail and the crab one of its claws to get away. In the same way, when awakened by the sacrifice of large populations, a living ·community should react with countermeasures. Unlike weeds or grasshoppers, however, human society loudly glorifies the dignity of the individual. In the Japa­ nese constitution, basic human rights are given the highest priority. Consequently, the development of all government and industry must be based first on a guarantee of b�sic human rights. In civilized human society, each individual's right to life is something sacred and inviolable. Thus it is not acceptable to wait for a dead center to develop in some great conurbation before recognizing a threat to human life and only then directing the whole nation's efforts into restor­ ing and protecting the natural environment and sacrificing some economic and industrial activity. Only recently have people with the affluent and conven­ ient lifestyle provided in rich countries by modern indus­ trial development come to assume that such a lifestyle is natural and the only kind of life worth living. Even if a few

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people in wealthy countries do give their attention to more serious matters, in the course of modern daily life most people become increasingly and thoughtlessly accustomed to luxury. Of course, during World War II in Japan, when both indi­ vidual lives and the life of the nation were threatened, it is true that people and communities resolutely accepted as inevitable compulsory action, such as evacuation programs. People who had spent their whole lives in urban areas like Tokyo or Kyoto gave up their homes, assets, and social position to go live in the mountains and dig potatoes­ because their lives were at stake. The people of today's overpopulated cities, who could not even be budged with a crowbar, as well as our leaders in politics, administration, and industry, posture arrogantly and refuse to listen to warnings from mere environmental­ ists. But someday, either suddenly or gradually without their realizing it, when the big cities and even their sprawling sub­ urbs develop their own dead centers, these leaders too will forget their speeches and make a run for whatever natural green environments are left-if they are lucky enough to find any. Then at least some of them will throw to the winds those assets that they now hold to be so indispensable. Even on such occasions, though, nature will apply over the course of time its powers of restoration, undisturbed by massive human confusion. In the midst of dead centers it will re-create new green environments, to the extent that soil remains and has not been irreparably paved over. After these places have been revived, surviving humans will start to extend their living space back into these same areas, timidly at first. But after several generations, tlJ_ey too will probably forget the painful experiences of their ancestors. They will again ignore the basic rules of natural systems, rejecting coexistence with the other members of the natural community-animals and plants. And when they have reas­ sumed this smugness, nature may again produce dead cen­ ters in order to restore its balance.

Versatility May Not Pay in the World of Plants

As we have seen, the habitat most favorable to a species, its physiologically optimal site, and the actual habitat where it competes fiercely with other plant species, its ecological habitat, are distinct for many plant species. In fact, most plants that can live in harsh environments are weak com­ petitors with other plants. By contrast, in the competition among plants with similar structure and ecological strategy, some species exhibit overwhelming strength within the lim­ ited range of their appropriate habitat conditions and force out all other plant species. Their ability to grow diminishes drastically, however, with any change in environmental conditions. Various evergreen oak species and trees such as beech are good examples of this phenomenon. In .their physiologically optimal habitats these species form the for­ est overstorey, capture the most sunlight and other resources, and dominate the whole vegetation stand by con­ trolling the growth potential of the smaller species. For them, the physiologically optimal habitat and the ecological habitat are one and the same. Species that can grow almost anywhere, though, are usually poor competitors and gener­ ally do not succeed in becoming the dominant species any­ where. In this sense, versatility does not pay in the world of plants. Quality and Quantity

In order to survive, humans need environments with suf­ ficient air, water, and food. Since time immemorial humans have struggled in particular to secure adequate food supplies. Our bodies require a variety of nutrients and other dietary components, such as carbohydrates, fats, proteins, and vita­ mins. We have met these needs mainly through agriculture, animal husbandry, fisheries, and other primary industries that rely on nature. In the past, sufficient and stable amounts of these components could be obtained without much trou­ ble just by eating a balanced diet of traditional foods. Now,

THE BLACK PINE GROVES ON THE SHONAN COAST

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however, artificially and chemically produced foodstuffs offer the potential for less balanced diets. For example, the amount of rice sufficient for one Japa­ nese for one year is about 150 kilograms. This amount is assumed to be in the form of storable grain and not rotted or infested with insects; about 400 grams is cooked and eaten each day. Thus, the 150 kilograms of rice are consumed grad­ ually. Like humans, plants also prefer nourishment in small amounts. In the past, if plants in our fields needed nitrogen or were deficient in potassium, we supplied these nutrients by providing compost or other natural fertilizer, which de­ composed slowly over time. Dissolving in water into a form that is easy for plants to absorb, compost gives plants small but constant supplies of nitrogen, potassium, phosphorus, and so on. When chemical fertilizers are used, however, the supply of nutrients is often irrational, as if a person were served his or her yearly 150 kilograms of cooked rice all at one time. What if you were like a plant and could not move, and you were given all your food for a whole year all at once? For two or three days you would eat all you possibly could, and then you would get a stomachache and diarrhea. Rats and ants would swarm over the giant pile of food, which would start to rot while you starved to death with nothing more to eat for the next 360 days. Or what if you had a year's worth of rice but it was locked in a steel box that could not be opened? In this case also you would starve. In any event, fertilizer must be delivered to plants gradually and dissolved in water so that it can be absorbed naturally, by osmosis, through the root hairs. The Black Pine Groves on the Shanan Coast '

On Japan's Pacific coast south of Yokohama, in Kanagawa Prefecture, there are sand dunes between Enoshima and the mouth of the Sakawa River. Plant communities along this Shanan Coast once grew in a natural zonation, forming parallel bands of different species. Nearest to the water's edge grew communities of kobomugi sedge, followed farther

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inland by communities of a beach morning-glory ( Calystegia soldanella) and sea pea (Lathyrus japonicus), then stunted roundleaf chaste-trees (Vitex rotundifolia), and finally by a strip of tall Japanese black pines (Pinus thunbergii). These bands of vegetation, starting with kobomugi sedge and end­ ing with black pine, represent typical beach vegetation that thrives amid the salty sea breeze and ocean spray. Farther inland were agricultural fields and rice paddies, productive because they were protected from the ocean by the strip of black pines. Also behind the pines grew ordinary land plants not particularly resistant to the sea breeze or other ocean effects. Beginning in 1928, for protection against high winds, storm surges associated with typhoons, and the force of possible tsunamis, personnel from the Kanagawa prefectural govern­ ment planted black pines along the Shanan beach dunes, right next to the sea. Before the pines could grow tall, how­ ever, the drifting sand buried them. The local managers then erected reed fences to keep the drifting sand out, but after two or three years the reed fences were also buried, and new sand dunes formed behind the fences. A soil research insti­ tute was commissioned to find a way to make the black pines grow more rapidly. Analysis of the site confirmed that it lacked nitrogen, as is usual in sand dunes, and the research­ ers recommended planting exotic leguminous trees such as the North American locust (Robinia pseudoacacia) and false indigo (Amorpha fruticosa) among the pines. Unlike most other plants, leguminous plants such as the locust tree have parasitic root bacteria that can fix elemental nitrogen directly from the atmosphere. The locust trees thus provided the black pines with nitrogen in the form of large volumes of nitric acid ready for their consumption-just as if huge amounts of freshly cooked rice were given to a human being. The black pines, whose ecological habitat is normally areas with rather poor soil, could not use all this nitrogen-but a community of nitrogen-loving weeds could and soon invaded the site. Various types of evening primrose (Oenothera), as well as weedy daisy-family species such as Sumatran

NO ADVANTAGE TO BEING TOO STRONG

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fleabane (Erigeron sumatrensis) and Canadian fleabane (Erigeron canadensis), spread thickly over the area, reach­ ing more than a meter in height and turning the place into a huge field of weeds. The black pines were left to eke out their existence, not really growing but not really dying, somewhere among the weeds and the locust tr.ees. Without any knowledge of chemistry, our ancestors devel­ oped the traditional method of spreading compost on fields numerous times in small amounts. It caused no extreme disturbance to the plant communities involved, unlike the attempt to manipulate the black,-pine groves. The safest way to manage the beach vegetation would have been as fol­ lows. The shifting of the sand could have been prevented by planting a strip of kobomugi sedge, a band of beach morning glories and sea peas, and then a strip of chaste-tree shrubs between the black pines and the water's edge. Humus from the fallen leaves should have been allowed to mix in with the soil, thus letting nature itself gradually enrich the soil. Then the vegetation could have been adjusted to shorten the distance between the water's edge and the black pines, while respecting the natural arrange­ ment of plants. No Advantage to Being Too Strong In plant communities a moderate degree of strength is more advantageous and healthy than too much strength, for both the species itself and for its community. Overly strong plants not only disrupt the plant community but also degrade the environment, jeopardizing their own survival. Much disrup­ tion happens as a result of single-purpose schemes thought up by humans who have good intentions but only a poor understanding of the natural order of the living community. Much of the Vienna Woods is composed of beautiful beech trees. At one time, though, the roadsides in the Vienna Woods were plagued by weeds, which became a big prob­ lem. In the 1930s the beech forest next to the road went into a slight decline. The park keepers thought it was probably

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due to a nitrogen deficiency. At that time, the nitrogen-fixing locust, from North America, was being widely planted in many countries to fertilize the soil (see the previous sec­ tion). When it was planted in the Vienna Woods, soil nitro­ gen levels temporarily rose. Soon, however, nitrogen-loving weeds like torch azalea (Rhododendron kaempferi) and Canadian fleabane invaded and took over the ·area, as in the situation that unfolded on Japan's Shanan Coast. The natu­ ral balance of the plant community was destroyed, and the forest itself was greatly damaged. Trees in a natural forest do not need large temporary sup­ plies of nitrogen; their leaves fall to the ground every year and break down into humus. The humus slowly decomposes, providing amounts of nitrogen adequate for growth. Forest fertilization has been tried recently in Japan, and initial results appear to show that tree trunks thicken .more rapidly under a fertilization regime. If a forest is regarded as a bio­ logical community of trees, shrubs, herbaceous plants, and so on, however, which coexist while competing with one another, one can see that the application of fertilizer can sometimes be harmful. If we are to guarantee a forest's sus­ tained growth, fertilization must be kept at a level that will not upset the balance and system of the biological commu­ nity. The Leucaena Trees of the Bonin Islands The Bonin (Ogasawara) Islands, located about halfway between Tokyo and Guam, came under U.S. military con­ trol after World War II; they were returned to Japan in 1968. Until the war, humans had lived on Chichi-jima, Haha-jima, and other islands and had destroyed the natural forests. By 1968 the islands were covered with dense forests or groves of leucaena trees (Leucaena Jeucocephala), native to the tropical Americas. Like the locust trees, leucaenas are legu­ minous trees and can fix nitrogen from the air, causing a temporary abundance of nutrients in the soil that some­ times prevents the growth of other trees.

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Just before the Bonin Islands reverted to Japan, a Japanese survey team and a group of journalists visited the islands. They reported that, on the islands that had been almost completely uninhabited for twenty-four years, natural for­ ests had recovered completely, covering these islands with "jungle." On July 30, 1968, five days after the reversion to Japan, the senior author of this book was suddenly invited to join a team from the Yomiuri Shimbun newspaper which would be visiting Chichi-jima, Haha-jima, and Ani-jima. At first we had to break through a zone five to ten meters wide made up of the kind of vegetation that grows on and just behind beaches almost everywhere in the tropics: a belt of a beach morning-glory (Ipomoea pes-caprae, also called bayhops; more cosmopolitan than and not to be confused with the Calystegia soldanella beach morning-glory men­ tioned earlier) on the beach itself and then a dense thicket of hard-leaved scaevola shrubs (Scaevola sericea). As expected, we then found thick forests of leucaenas three to eight meters tall. It was so hot in the forest that we perspired pro­ fusely. On the completely windless floor of the forest, we saw the shells of agate snails imported from Africa and mounds of earthworm castings, but almost no plants, other than a few sprouts of leucaena. Leucaena leaves are high in protein and, after falling, are soon broken down by decom­ poser organisms. The soil was rich in nitrogen and must have been extremely fertile. The Bonin Islands are home to a great many endemic species, including nearly a hundred woody plant species alone. In twenty-four years, in light of the first survey team's report, the local species and communities should have forced out the leucaena and other exotics and changed the forest into one that included Bonin endemics. Where the natural forest had been eliminated and replaced by leu­ caena forest, however, the development of a natural plant community was observed almost nowhere. On Haha-jima in particular, in the shade of the "restored" dark-green jungle, the stone walls of former villages, town halls, and schools were the only remaining signs of previ-

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ous inhabitants. Except for hernandia (Hernandia sonora), Alexandrian laurel (Calophyllum inophyllum), Chinese ban­ yan (Ficus microcarpa), beach hibiscus (Hibiscus tiliaceus), Ogasawara fan palm (Livistona boninensis), and other trees that had been planted (all typical tropical-Pacific coastal species), most of the trees covering the landscape were introduced species such as leucaena. To the casual observer it did indeed appear as if the "jungle" had returned, but qualitatively these leucaena forests were completely differ­ ent from the original natural forests of endemic Bonin trees and other plants. In terms of plant sociology and community integrity, nature had not recovered-it had been confused. Like the locust trees in the Vienna Woods, the leucaena trees were brought in by humans. During the Pacific War a fast-growing tree was needed to camouflage gun batteries and pillboxes so that they could not be seen by enemy air­ craft. Leucaena was imported for this purpose, perhaps from Guam. The agate snail was also imported during the war, accidentally, in emergency food supplies. By the time the islands were returned to Japan, the voracious snail had spread everywhere, making it impossible to grow vegeta­ bles. Unfortunately, the taste of the snail is so bad that it cannot even be used as fish bait. Humans, assuming that the schemes they think up will work out just fine, often find that their brilliant ideas do not mesh well with the diverse systems of nature. The laws of nature must be learned from nature-and with respect to vegetation, the only schoolroom where one can learn the truth is out in the field. On the slopes of Mount Yoake on Chichi-jima, around the sites of gun batteries and other installations of the Japanese Imperial Army, we found planted leucaena trees still grow­ ing in the excavated earth. More than twenty years after the war the military installations had disappeared, but the leu­ caena groves could be distinguished from the surrounding natural forest even from far away. We could confirm where the military installations had been by looking at the vegeta­ tion. As the German army reportedly had done in some

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places in World War II, if the U.S. Army had sent plant sociologists or other vegetation specialists over the island in airplanes, the exotic leucaena groves, rather than serving as camouflage, would have given away the concealed installa..: tions immediately. The leucaena groves had become well established over large areas where the original natural forests had disappeared, bringing the redevelopment of natural plant communities to a standstill. Leucaena, like the locust tree, is apparently too strong a species. Many of the component plant species in natural forests are able to grow in understorey shade. They grow slowly during their early years. By contrast, the first species to invade places where the natural vegetation and physical environment have been degraded are pioneer species that can grow in (and may require) direct sunlight. Their growth during their early years is rapid. Such species normally have only short lives, however, because the seedlings and saplings of sun-loving species cannot grow well in the shade cast by adult trees, even those of the same species. Instead, only species that can grow in shade can thrive under other trees, so such places eventually become forests of shade-tolerant tree species. In about ten years, larger leucaenas grow seven to eight meters tall; in due time they die off, after bearing many pea­ pod-like fruit,· which are black when ripe. Under locust or leucaena trees, though, the soil becomes excessively fertile through· the workings of the nitrogen-fixing bacteria. The components of natural forests, which normally grow in moderately fertile to poor soils, do not particularly flourish in soil containing an overabundance of nitrogen. But the fast-growing leucaenas, which are adapted to high nitrogen levels, sprout abundantly in such soil and grow rapidly, eventually covering the area again. Nitrogen Pollution by Civilization We cannot overlook the problem of soil overfertility caused by the proliferation of nitrogen that results from human activ-

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ities. Diverse plant communities do not usually suffer too much from impoverishment of the soil; for them, the worst sort of pollution is overfertilization, especially an overabun­ dance of nitrogen. Natural areas normally have moderately fertile to poor soils. Many plant species and communities coexist in these areas, segregating their habitats and adjust­ ing to even slight changes in the topography. They coexist in diverse natural systems and maintain their equilibrium, whether they are in forests, grasslands, marshes, or any other kind of environment. Introduction of too much nitro­ gen (or other major nutrient) can reduce a diverse natural ecosystem to a much simpler, more uniform system by per­ mitting only a few species (perhaps only one) to outcom­ pete the others, force them out, and gain dominance. A familiar example of this phenomenon involves crabgrass (Digitaria ciliaris), which in summer covers agricultural fields in farms all over Japan and invades lawns in the southern United States. Human destruction of nature through an overabundance of nitrogen does not occur only in fertilized agricultural fields and leucaena plantations. Most country roads, many roadsides, and vacant lots in cities have a temporary over­ abundance of nitrogen and become covered with weedy plants, such as the exotic tall goldenrod (Solidago altissima) from North America. Humans (and perhaps particularly the Japanese, who are descended from an agricultural people) have traditionally viewed the plant world as consisting of planted trees, garden flowers, agricultural fields, and rice paddies. Thus our thinking about the natural world of plants is obsessed ·with removing weeds, we feel that trees are things to be pruned, and we believe that to improve natural plant life we must fertilize. In Japan, enormous amounts of chemical fertilizer (mainly nitrogen) are applied in rice paddies, which surprises and worries foreign specialists. Fertilizer is also assumed to be necessary for the grass and other greenery planted on slopes where roads have been built and, recently, even in managed

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forest areas. In agriculture, we force plants to grow as quickly as possible, in order to satisfy our desire for increased pro­ ductivity. Fertilizer may be necessary in monocultures of rice or vegetables, or in decorative plantings of our favorite flowers and shrubs. In maintaining or restoring plant diver­ sity in accordance with nature's original characteristics, however, nitrogen fertilizers, and in particular chemical fertilizers, may in the long run be harmful and should be used with as much caution as possible. For plants, as for human beings, an overabundance of nutrients is a sure sign of trouble.

Chapter 3 Mantle and Fringe Communities

Forests Destroyed by Roads for Tourism In the 1960s and 1970s, roads were built that bit deeply into the last of Japan's high-altitude and other inland forests that had remained close to their original, natural state. Some roads were for -tourism, but others, called "super forest roads," were meant both for tourism and for trucks hauling logs or other freight. More recently, mountain roads have been con­ structed with greater, but still insufficient, consideration for the environment, and roads like these have been planned for the entire archipelago. On the main island of Honshu, some of these roads have been built through subalpine conifer forests, which grow more than 1,500 meters above sea level and are dominated by beautiful trees such as Veitch's silver fir (Abies veitchii) and Maries' fir (Abies mariesii). In northeastern Hokkaido such roads have been built through boreal coniferous forests dominated by Yezo spruce (Picea jezoensis) and Sakhalin fir (Abies sachalinen­ sis), which can grow at lower altitudes approaching the sea­ coast as well as in higher areas. Mount Fuji (3,776 meters) is the highest mountain in Japan. The Fuji-Subaru Line, a tourist toll road on the northern slope of Mount Fuji, was completed in 1964, is open only to cars, and is paved all the way up to Komitake Shrine, at an altitude of 2,400 meters. Every year many trees along this road turn brown and die. Although the road was built 101

10 2 MANTLE AND FRINGE COMMUNITIES

to enable people to enjoy the beautiful scenery of a natural forest, the area has become a landscape of death. Examples of remnant natural forests destroyed by the construction of toll roads can be found everywhere in Japan. In particular, the building of a dangerous, ugly road 2,800 meters above sea level on Mount Norikuradake, a major volcano, has dev­ astated plant life on both sides of the road. No attempt has been made to repair the damage. The Suzuran Forest Road in Nagano is also especially awful in this respect. Although relatively resilient natural environments may easily survive road construction, more sensitive areas are quite vulnerable. In such cases, if typical methods of indus­ trial and regional development are applied regardless of soil or topography, the construction of even a single road can wreak incalculable damage on the natural environment. And when that damage wipes out the tourism resource that was the reason for development in the first place, and large economic outlays must be made to restore and maintain the ruined natural features, then the result is a net loss to the human community and to its economy as well. Along the high-altitude roads on Mounts Fuji and Norikuradake, where winters are long and harsh, stands of Maries' fir, Veitch's sil­ ver fir, and northern Japanese hemlock (Tsuga diversifolia) huddle in dense groves to withstand the blizzards, at the very edge of survival. This is an extremely fragile plant community. The Fuji-Subaru Line is the first road construc­ tion project in Japan aimed at tourism in the midst of such a delicate landscape. Other countries have also constructed roads through sub­ alpine and alpine areas, for example, across the Alps or Pyrenees, where roads have been built for ages. Why has there been no damage there comparable to the tree death along the Fuji-Subaru Line? Europeans' natural methods of restoration and rational road construction within the lim­ ited spatial systems of plant communities are probably the result of long years of experience, trial and error, and the consolidation of findings in biology, phytosociology, and landscape management, fields that developed during the

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twentieth century. Methods of development and restoration that fit the spatial dimensions of plant communities are something to aim for. Simply devising symptomatic relief for particular phe­ nomena, such as trees dying along roads through forests, is a mistake. As soon as one measure is implemented, more instances of forest damage and other environmental destruc­ tion will follow endlessly. The real reason why trees die along forest roads must first be identified and publicized. When a natural forest is located next to an open area, such as a meadow or road, a belt of light-demanding, shade­ intolerant shrubs and vines always grows between the for­ est and the open area, forming a specialized community called a mantle community. Around this skirt-like mantle community grows a hem-like community of herbaceous plants called the herbaceous fringe community, or smzm (in the original German). These two forest-edge communities are shown schematically in figure 8. Normally, the species of these communities are peculiar to the forest margin and differ from those of the adjacent forests and also from the species that grow in the adjacent open spaces. These edge communities, which appear to obstruct the forest's growth into the open spaces, actually protect the forest against the abrupt changes in environmental conditions that occur between the forest interior and the open area, in particular against the drying effects of the strong sunlight and wind found outside the forest. If a natural forest is destroyed, as by typhoon, flood, fire, or human activities, it is soon enclosed again by natural mantle and fringe communities, composed of plants that grow best in sunlight or only par­ tial shade. These communities are thus like a scab protect­ ing a wound. Forests, like people, can heal themselves. When a road is built through a dense forest of tall trees protected by these edge communities, the construction opens up spaces between the trees. Immediately, strong wind and light penetrate the forest. Some of the trees are blown down, the forest· floor becomes drier, and the biological community is thrown off balance. Damage is caused not

Figure 8. Mantle and fringe vegetation (shirakashi oak forest) evergreen oak

castanopsis

wild camellia

1-1-1 mantle community

fringe community

Closed mature forests are relatively dark inside, so light-demanding species occur only in characteristic mantle and fringe communities that cover the forest edge. In the case shown here, typical of the Tokyo area, the forest is an evergreen forest of shirakashi oak and castanopsis, with shade-tolerant shrubs such as wild camellia in the understorey. The mantle community is formed mainly of deciduous shrubs and vines, the latter climbing or sprawling on the exposed forest edge. The fringe community is composed of herbaceous perennial species that grow outward from the edge of the mantle.

only directly by the construction process but also indirectly by its aftereffects. As dead trees fall, the wound widens, penetrating deeper into the forest every year. On steep slopes where the road forms winding hairpin curves, dam-

THE MANTLE COMMUNITY

105

age from fallen trees extends both up and down the slope on both sides of the curve. In time the slope between these upper and lower areas becomes completely denuded. With the removal of the living network of tree roots that holds the soil, the danger of landslides onto the road increases. Examples of forest-margin communities being devastated by road construction are not confined to subalpine areas. In Japan such damage occurs also in beech forests on the lower slopes of mountains in Honshu, at altitudes of 800 to 1,600 meters. There are so many examples of this destruc­ tion that they are difficult to count. Compared with the sub­ alpine belt and above, the vegetation in these lower areas grows under more favorable environmental conditions and has stronger powers of resistance and recovery. Thus, tak­ ing even the least care with the spatial structure of the bio­ logical communities during road construction and subse­ quent maintenance would have prevented the chronic dying off of trees and resulting landslides. The Mantle Community

When a natural, closed-canopy forest is next to a rocky field, river, lake, pond, or bare or other open area, there is always a buffer of shrubs, vines, and herbaceous plants between the closed forest and the open area. At the edges of pastures, agricultural fields, or other artificial open spaces next to groves of trees, in time there always grows up a char­ acteristic mantle community, composed of vines, shrubs, and light-demanding or light-tolerant trees. These mantle species differ from the pasture grasses and field weeds that grow in open green areas, and they differ from the trees of the closed forest. In the evergreen broadleaf forest zone where most ,Japa­ nese live, representative mantle community species include vines such as kudzu (Pueraria lobata), Japanese wild grape (Ampelopsis glandulosa var. heterophylla), ebizuru grape­ vine (Vitis ficifolia), Chinese fevervine (Paederia scandens),

106 MANTLE AND FRINGE COMMUNITIES

sweet autumn clematis (Clematis ternij].ora), hops (Humulus scandens), three-leaved akebia (Akebia trifoliata), and Japanese cayratia (Cayratia japonica). Low trees and shrubs in such mantles include Japanese snowflower (Deutzia cre­ nata), Roxburgh sumac (Rhus javanica var. roxburghii), Korean weigela (Weigela coraeensis), Harlequin glory bower (Clerodendron trichotomum), Japanese mallotus (Mallotus japonicus), early stachyurus (Stachyurus praecox), palm­ leaf bramble (Rubus palmatus var. coptophyllus), Chinese mulberry (Moms australis), a Japanese cat-briar (Smilax riparia), and spindle tree (Euonymus sieboldianus). Most of these plants can grow in a wide range of environmental conditions, provided that there are no competitors. Thus they are the first perennial vines and shrubs to appear in a newly cleared open space, rapidly covering the exposed bare land that has been scraped clean by a flood or by human activity, just as the healing process closes· a wound when one's skin is cut. In Japan, the groves around temples and shrines which dot towns, villages, and paddy fields like miniature green islands, have generally managed to maintain a relatively natural state up to the present, despite being surrounded by open landscapes. This is because the mantles surrounding the groves have been sufficiently preserved. Some of these small, well-preserved forests have been designated as natu­ ral monuments, but then they often have been protected and managed too much, resulting in their demise. From the human point of view, the mantle communities on forest margins, and particularly the vines, have a shabby and unpleasant appearance. Surmising that these plants are unwanted intruders in evergreen castanopsis and laurel groves, humans remove the forest-margin communities and undergrowth. But plants that appear to be competitors may actually represent important patterns of coexistence in the community and should not be destroyed out of ignorance (or arrogance). When they are removed, light and wind sud­ denly begin to penetrate the forest, the forest floor dries out, and the whole forest itself is eventually destroyed.

Conditions for Growth of Mantle Communities

Normally, the plants that make up the mantle community have strong powers of resistance (endurance) with respect to environmental conditions and can grow anywhere, from places with fertile soil to areas where the rich topsoil has been stripped off. In competition with other plants, how­ ever, they are rather weak. They cannot grow in a stable for­ est for lack of light, but are pushed out to the forest margin, where there is more light. In some environments with con­ ditions too severe for forests, only herbaceous plants can grow, as for example on rocks where there is almost no soil, on cliffs where the wind is too strong, in areas where the soil is too dry, on beaches where the sand is constantly shifting, or on seaside cliffs constantly exposed to salt spray. Mantle communities also cannot grow in such situations, but low-growing herbaceous plants may manage to survive, even though they are even weaker competitors than are the mantle species. When the fallen leaves from the herbaceous plants have accumulated to form some soil, however, slightly improving the environmental conditions, mantle species may then invade the area and eventually dominate it. When envi­ ronmental conditions improve further, to the point where forest species can survive, the mantle species are again pushed out to the edge and grow in a border strip between the herbaceous and forest communities. This mantle strip helps the advancing forest by forming island-like outposts as it invades the herbaceous zone. When the borders of an open area are naturally abrupt, as with pastures, fields, trails, or rivers, which are regularly grazed, plowed, walked on, or flooded, the mantle commu­ nity does not form buffer strips with islands of advance veg­ etation. In these cases it is arranged in a relatively straight line along the field, trail, or river. Thus the species that make up the mantle community are forced to hang on somehow in a narrow strip at the margins of the forest. This· is not their physiologically optimal habi­ tat. Given the opportunity, they would both spread out into

108 MANTLE AND FRINGE COMMUNITIES

the forest and try to grow as thickly as possible on open ground. Environmental conditions in quite open areas, how­ ever, are usually too severe; it is also normally impossible for mantle species to spread out onto trails, where there is repeated human disturbance. In former open spaces where human intervention has diminished, as in abandoned agri­ cultural fields, mantle species immediately start to grow and completely cover the site in two or three years. This is something anyone can see in his or her own neighborhood. When natural forests particularly suited to a location are cut down and replaced by plantations of exotic tree species, the plantations have to be kept clear of weeds for several years or even longer. This prevents mantle species from growing up so thickly that they force out the seedlings and young trees that have been brought in. Even when the seed­ lings grow into young trees, they will be invaded by mantle species if the trees were not planted densely enough. This is because a tree plantation, unlike a natural forest, repre­ sents a separate overstorey tree layer that cannot form a har­ moniously balanced plant community with the particular understorey, shrub, and herbaceous layers suited to the loca­ tion. Certain mantle species quickly thrive in such planta­ tions and may dominate as if they were original species of the plant community natural to the area. In the diluvial uplands of the Kanta region and through­ out Honshu, Shikoku, and Kyushu, secondary forests of deciduous Japanese chestnut oak (Quercus acutissima) and konara oak ( Quercus serrata) grow where the natural forests were obliterated. Their secondary growth has been regu­ larly harvested for firewood and charcoal on a cycle of fifteen to twenty-five years. The regularity of the human disturbance, and the fact that it was not too frequent, has maintained these forests in balance over many years. These are representative examples of substitute plant communi­ ties. Although not original primary forests, some are never­ theless old-growth forests, with konara and chestnut oaks, Japanese storax (Styrax japonicus), stone fruit (Prunus

RESTORING PLANT LIFE ALONG ROADS

109

jamasakura), and other trees in the overstorey layer, plus

mantle species in the shrub layer, such as Japanese snow­ flower, cherry silverberry (Elaeagnus multiflora), Roxburgh sumac, Ussurian cat-briar (Smilax riparia var. ussuriensis), and winged spindle tree (Euonymus alatus). Vine species from the mantle community, such as Japanese mountain ebizuru grapevine, Japanese wild grape, three-leaved akebia (all mentioned above), and Japanese wisteria (Wisteria floribunda), also occur in these chestnut oak-konara oak forests. Indeed, these mantle species constitute a most important component of the forest. In the same way, in the red-pine (Pinus densiflora) forests of the Kansai region of western Japan, between Osaka and Hiroshima, there is an admixture of mantle species such as palm-leaf bramble, Japanese snow flower, three-leaved akebia, Roxburgh sumac and tricho_carp sumac (Rhus trichocarpa). Restoring Plant Life along Roads We can see that not much effort is required to restore plant life along roads through semi-natural or secondary chestnut oak-konara oak forests or red-pine forests in Japan. A great deal of light already shines into a secondary forest com­ posed of such light-tolerant trees, and a high diversity of mantle species is already present. Left to themselves for three to five years, these plants will re-green and restore the damaged places. The most beautiful example of this process can be seen in the forests of torch azalea (Rhododendron kaempferi) and Japanese red pine growing along the Fuji­ Subaru Line on Mount Fuji, in a lava field at Kemmarubi, 800 to_l,200 meters above sea level. The Fuji-Subaru Line was constructed uniformly, using the same methods along the whole road, from an elevation of 800 meters almost up to the alpine tree line at 2,400 meters. The subalpine conifer forests of Veitch's silver fir and northern Japanese hemlock, which grow above 1,800 meters and are as vulnerable as our eyes, suffered terrible destruc-

110 MANTLE AND FRINGE COMMUNITIES

tion along these roads. Though many years have passed since the roads were built, one can still see dead and fallen trees along them. The red-pine forests in the Kemmarubi area, with their naturally high resistance, however, have been restored by the natural mantle vegetation. Before such roads are built, the restorative powers of the plant communities should be examined, ecologically and phytosociologically, and the results made easily compre­ hensible to both ordinary people and highway engineers. This information would normally be displayed in the form of maps or diagrams of the plant life, which would caution against routing a road through areas of vegetation with weak restorative potential and would clarify the need for careful restoration of the mantle community along the road. It is not necessary to reestablish the mantle community uni­ formly all the way from the bottom to the top. If a vegeta­ tion map is made before construction is planned, it can serve as a diagnostic chart showing the relative strengths of the various natural communities. For example, unnecessary effort could have been avoided by foreseeing that the red­ pine forests along the Fuji-Subaru Line could be left to restore themselves naturally. Mantle species usually grow quickly, and as long as competing plants are kept down, they will grow well in any newly barren ground. Beautiful Women and Clothes Some men look more oafish than ever in stylish clothing; some women look more beautiful than ever in the plainest outfit. Women with a sense of beauty know themselves and understand how to wear clothes to express the best points of their personalities. Thus, in women, beauty does not mean a certain standardized appearance or concept but rather a kind of beauty derived from their own personalities. Nature is even more variously beautiful and enchanting. No matter how we damage the earth's natural forests, mantle vegetation suited to each location appears afterward. Where

THE FRINGE COMMUNITY

111

natural forests have been cleared for open landscapes, such as for housing or agriculture, mantle vegetation grows up between the fields and in hedges around the houses. Even where the natural forest has been utterly wiped out, we can determine what kind of forest it was by looking at the sub­ sequent mantle community and its component species, so characteristic are they. Similarly, when we travel through Japan by train, from south to north, or by car or on foot from the lowlands to the highlands, we can tell which forest zones we are passing through by the component species of the mantle communi­ ties we see along the way. In the evergreen broadleaf forest zone, the prominent mantle vines we notice are kudzu, hops, Japanese wild grape, and Japanese cayratia. In the beech for­ ests of the deciduous broadleaf forest zone in central Honshu, at an altitude of 800 meters or higher, the main vine species of the mantle along the forest margin and trails are Japanese mountain grapevine (Vitis coignetiae) and kolomikta-vine (Actinidia kolomikta). Then, as we approach the boreal-like subalpine conifer forest belt above 1,600 meters, the vines change again, primarily to kurozuru ( Tripterygium regelii, family Celastraceae). This journey shows us that the species composing plant mantle communities have wide potential ecological ranges. In the natural world, though, they interact with the forest and other mantle species, which draw unequivocal boundaries around the areas where the mantle species can actually live. To successfully restore vegetation along forest roads, the mantle community appropriate to the particular zone must be used. The Fringe Community

Surrounding the mantle communities of shrubs and peren­ nial vines that grow along the edges of forests and hedge­ rows is another border, one composed of herbaceous annual plants such as yaemugura (Galium spurium var.

112 MANTLE AND FRINGE COMMUNITIES

echinospermon) and hedge parsley (Torilis japonica or T. scabra), and herbaceous perennial plants such as jointhead arthraxon (Arthraxon hispidus), sweet flag (Rubia akane), and field horsetail (Equisetum arvense). This herbaceous border pins down the hem of the mantle community, using the space between the shrubs of the mantle and the open ground beyond. This group of plants is the (herbaceous) fringe community, or saum (see fig. 8). Just as the mantle protects the forest edge, this herbaceous fringe helps keep the soil under the mantle plants from drying out. Like the component species of all other plant communi­ ties, the plant species making up the fringe community try to expand their share of living space by dispersing as many seeds as they can and by extending their roots as far as pos­ sible underground. These herbaceous plants, though, nor­ mally require a location with rich soil which, at the very least, has abundant nitrogen. Although generally tolerant of full sunlight, the fringe species also thrive in the partial shade under the shrubs of the mantle community. At the edge of a forest a plentiful supply of fallen leaves always collects. This organic matter, or litter, decomposes in a complex series of processes. For its nutrients to become available to living plants, the litter must be broken down, or mineralized, into mostly inorganic compounds that can be dissolved in the water that is present in the soil and then taken up by plant roots. Mineralization is complete only after the litter has passed many times through the digestive systems of soil-dwelling creatures such as earthworms, mil­ lipedes, and rotifers and has been processed even further by fungi and bacteria that live in the soil. Life thrives most at the edge of a forest, where huge num­ bers of soil-dwelling insects, bacteria, and other microor­ ganisms perform an extremely diverse variety of functions. For plant species that normally grow in open fields or grass­ lands, though, there is not enough light at the edge of the mantle. The fringe species populate this limited space, filling the narrow borders around forests and hedgerows with life. Even more precisely than those of the mantle,

TREES PLANTED INAPPROPRIATELY DO NOT LAST LONG

113

these fringe species indicate the potential vegetation and the particular conditions of the site. When a closed forest is cleared and open ground or a bar­ ren area is created, as when a road is built, the first plants to grow up along the forest edge are those belonging to the fringe community. If the spatial structure of plant commu­ nities is not understood sufficiently, both fringe plants and mantle plants are usually perceived as weeds. Money is then allocated to cut them down, in spite of their protective function, thus aggravating damage to the remaining forest. Trees Planted Inappropriately Do Not Last Long In the four or five years following the construction of the Fuji-Subaru Line, the subalpine conifer forest lining the road continuously declined. Hoping to minimize the dam­ age, I lectured on television about the importance of mantle and fringe communities. Sure enough, I soon got a call from the local managers asking me to accompany them to the site. They said, "As you can see, road construction opened up these gentle slopes, which we planted with Japanese lawn grass. But it has· all died, and the slopes have become cov­ ered with nothing but weeds. There seems to be no help for it, so every year we apply for a budget and clear the weeds and fallen trees. As you can see, though, the forest keeps dying off." Blood closes a wound by coagulating and forming a scab; if one picks off the scab, the wound re-opens and perhaps becomes larger. That was just what was happening along this road on Mount Fuji. Japanese lawn grass (Zoysia japonica), is the main component of a substitute plant community found throughout Japan at altitudes below about 1,500 meters, in the beech-and-oak forest belt. It cannot survive above 1,600 meters, in the subalpine conifer forest belt, and thus on Mount Fuji it promptly died. And the "weeds" that the man­ agers were spending money to remove-the fujitenninso mint (Leucosceptrum japonicum form. barbinerve), hosoeno­ azami thistle (Cirsium effusum), Hakone calamagrostis grass

114 MANTLE AND FRINGE COMMUNITIES

(Calamagrostis hakonensis), Japanese knotweed (Reynoutria japonica), Japanese strawberry (Fragaria nipponica), yama­ shirogiku aster (Aster ageratoides ssp. amplexifolius), and other herbaceous plants (all without English names)-were actually functioning as the initial "scabbing" mechanisms in the process of sealing off the damaged forest edge. In nature, land does not want to remain barren. When a bare spot has been created in the middle of a forest due to roads or logging, nature cannot immediately restore the for­ est to its original state but does hurry to cover the spot with mantle and fringe communities. So we do not have to expend money and effort to regenerate these edge commu­ nities-all we have to do is stay out of nature's way and let the forest heal itself. In the barren areas along the subalpine road on Mount Fuji, the natural healing process would unfold as follows. First, herbaceous fringe-community species would form small islands, like stepping-stones. These species would include pearly everlasting (Anaphalis margaritacea var. angustifolia), Hondo campanula (Campanula punctata var. hondoense), oyomogi (Artemisia montana), alpine ragwort (Senecio nemorensis), and hagakuresuge sedge (Carex jacens). When fringe plants had grown in to a certain extent and the soil had stabilized, mantle species would start to take root and the forest edge would recover in stages. This second wave of growth would include species such as hawthorn-leaf black­ berry (Rubus crataegifolius), Japanese angelica tree (Aralia elata), Tschonosky privet (Ligustrum tschonoskii), bakko wil­ low (Salix bakko), Fuji cherry (Prunus incisa), and Japanese rowan (Sorbus commixta). Next, light-tolerant taller trees such as Matsumura alder (Alnus matsumurae), Manchurian alder (Alnus hirsuta var. sibirica), monarch birch (Betula maximowicziana), and Erman's birch (Betula ermanii) would grow in, to complete the mantle covering the edge of the damaged forest. The component species of the fringe community that once covered the barren ground completely would be pushed far­ ther outward as the forest and mantle communities stabi-

TROPICAL JUNGLES ARE USUALLY CREATED ARTIFICIALLY

115

lized. Thereafter the fringe species would be confined to the narrow space between the mantle and the open ground, fulfilling their function of holding down the hem of the mantle. When mantle and fringe communities had grown in sufficiently, even a closed-canopy forest adjacent to a road or other open ground would be adequately protected, and instances of blighted and fallen trees would decline dramat­ ically. Tropical Jungles Are Usually Created Artificially

In Malaysia, Indonesia, the Philippines, and other parts of Southeast Asia, large areas have been made barren by human activities, after which alang-alang grass (Imperato cylindrica) has been planted. This is a serious problem because the arti­ ficial grasslands thus created can be very stable, often mak­ ing the change irreversible under normal conditions. Between these grasslands and the remaining tall forest grows a real jungle of mantle species, mainly a wide variety of vines. Gen­ tly sloping, slash-and-burn fields that have been abandoned also take on the appearance of dense, unbroken jungle. Through central and northern Thailand, a paved military road built by the U.S. Army to link various bases seems to extend endlessly from Bangkok northward. The old-growth forests remaining in the mountains along the road have been burned down or cleared away. Here and there, large trees still stand at the edges of these clearings, like huge poles. Between them, vines and shrubs grow luxuriantly, tumbling in curtains between the isolated trees and forming an impenetrable jungle. If you walk into the remaining natural forests, it may seem to you that trees and other plants are growing in promiscu­ ous confusion. From a physiognomic point of view, how­ ever, they form from five to as many as seven identifiable layers, including emergent trees, a canopy or tree overstorey, plus tree, shrub, and herbaceous understorey layers. These plants have neatly divided up the living space among them­ selves, each pursuing its life as one member of an interre-

116 MANTLE AND FRINGE COMMUNitIES

lated community of forest vegetation and contributing to the maintenance of the overall dynamic balance. Space in the forest is used efficiently, and there are no concentrations of species, unlike the situation in the tangled jungles at the forest edge. The reason for the difference between those jun­ gles and the orderly forest interior is that the edge receives an abundance of very bright sunlight, so even the thick stems and leaves of light-tolerant mantle species allow enough sunlight to shine through for photosynthesis by the plants underneath. At-the edge there is also plenty of soil and inor­ ganic nutrients. By contrast, in a natural tropical evergreen broadleaf forest, sunlight falls perpendicularly on the foliage of the emergent, overstorey, and sub-canopy tree layers. Most of the light is absorbed by the many layers of leaves in the upper levels and hardly reaches the shrub and herbaceous layers at all. The forest floor is covered mainly by shade­ tolerant plants that do not grow profusely; thus no impene­ trable jungle is formed. Mantle and fringe communities grow thickly along roads and rivers in natural tropical forests, so it is difficult for a person to penetrate the forest. But once inside the forest proper, he or she finds that the shrub layer is not very thick and it is easy to walk through the forest. From tropical to temperate and subpolar zones, all forests are surrounded by their own uniquely composed mantle and fringe communities, which are part of the original and potential forest life of each locality. The organization of plant communities everywhere follows the same basic patterns. In tropical areas where the natural forest has been logged or where open vegetation has been created artificially by burn­ ing, as for farmland cir pastures, native mantle-community species, mostly vines, grow on the forest edge. Beyond the mantle grow suitable herbaceous plant species, forming the fringe community.

Chapter 4 Temporal Vegetation Succession and Substitute Plant Communities

The spatial arrangement of vegetation can easily be observed in the field by comparing the relationships within each type of plant community to those in its neighboring plant com­ munity. If we look at vegetation in terms of its existence over time, however, can we say that it changes? If it does change, then how? What systematic laws govern the sequence of changes? Biological communities and their individual components develop over time. Communities eventually reach a peak of maturity and disappear, giving way to different species. Though constrained by their physical environments, com­ munities also modify their environmental conditions, how­ ever slightly, until the conditions become more suitable for the community's growth. These improvements help the par­ ticular communities groyv but also bring about their eventual demise, by making conditions better for other species. For example, when the lava from a volcanic eruption has been weathered to create enough inorganic soil, the first plant community appears and soon begins to amass organic mat­ ter by dropping its dead leaves and branches on the ground, thus enriching the soil. These first colonizers are mostly annual herbaceous plants which die after one growing sea­ son. When they have finally made soil rich enough for their own optimal development, however, the improved soil can also support stronger types of plants, such as perennial herbs 117

118 SUCCESSION AND SUBSTITUTE COMMUNITIES

and small shrubs. These plants then outstrip the original community and eventually replace it. Like the communities, the overall system is also constantly changing. It is impossible to permanently halt these changes in community composition. For example, communities of annual weeds give way to communities of perennial herbs, which in turn give way to shrub communities. This process of one plant community undergoing a compositional change and being replaced by another community is called succes­ sion. The plant community and the physical. environment continue to interact until the final community most appro­ priate for the environment comes into being, one that cannot be replaced by other plant types. In regions with sufficient precipitation and soil, the final community is a forest, with at least somewhat light-tolerant overstorey trees and more shade-tolerant understorey trees. Maintaining Existing Conditions

The only sure way to maintain an existing plant or human community and obstruct its succession to a new commu­ nity is to prevent it from improving its environmental con­ ditions too much, keeping it instead at some point just before its optimum. The force that pushes communities toward destruction and succession works through mechanisms of excessive growth. Ironically, it is the suppression of this excessive growth that rejuvenates existing communities and allows them to persist. For example, the weed communities that normally appear in agricultural fields, including such quick-growing annuals as crabgrass (Digitaria ciliaris), Ori­ ental lady's thumb (Persicaria longiseta), and portulaca (Portulaca oleracea), have flourished for thousands of years despite farmers' constant efforts to eliminate them. Ever since agriculture developed, this process has been repeatedly cre­ ating conditions that come just before the excessive-growth phase for these species. As a result, these species have become cosmopolitan, flourishing in agricultural fields all over the world.

MAINTAINING EXISTING CONDITIONS 119

One sure way to eliminate weeds completely from fields and gardens, and the most thorough way, is to stop pulling them up. When a field is abandoned, the usual weeds such as crabgrass will grow more luxuriantly than ever during the first year. As early as the following year, however, taller weeds normally found on roadsides and other open ground replace the annual weeds and become the dominant spe­ cies. In Japan, such taller weeds may include, Canadian flea­ bane (Erigeron canadensis), daisy fleabane (E. anmzus), and Sumatran fleabane (E. sumatrensis). Four or five years later, perennial herbaceous plants grow in, such as the grasses miscanthus (Miscanthus sinensis), alang-alang (Imperato cylindrica), and todashiba (Arundinella hirta). Mantle spe­ cies take over next, including early stachyurus (Stachyurus praecox), Roxburgh sumac (Rhus javanica var. roxburghii), and kudzu (Pueraria lobata). Then, in ten to fifteen years, the succession has proceeded far enough that a coppice-like growth of konara oak (Quercus serrata) and Japanese chest­ nut oak (Quercus acutissima) is formed. Finally, after eighty to a hundred years, a natural forest suited to the par­ ticular climate develops. In much of southern and western Japan, partly including the Kanta region and certainly west of it, this forest will be an evergreen broadleaf forest, which along the coasts is composed mainly of castanopsis species and tabunoki laurel (Persea thunbergii), and inland of ever­ green oak species. If farmers who tried in vain over hun­ dreds of years to eradicate weeds had simply let their fields lie fallow, the weeds would have thinned out remarkably in just two or three years. After ten years not a single indi­ vidual of those problematic weed species would have remained. The same can be said for plantain (Plantago) communi­ ties, which grow where people or animals are constantly walking, such as on footpaths and playing fields. This vege­ tation, also known as a "trampling community," is very low growing, is essentially all non-woody, and includes yard­ grass (Eleusine indica), annual bluegrass (Poa annua), and prostrate knotweed (Polygonum aviculare), in addition to the

12 0 SUCCESSION AND SUBSTITUTE COMMUNITIES

plantain (mainly Plantago asiatica). Plantain communities occur worldwide and can be seen, in essentially the same form, from Japan to the suburbs of Paris and rural roads of England. In Japan, from Okinawa in the south to Hokkaido in the north, plantain communities are composed mostly of the same species. They are specialized to grow next to open ground and can endure being co11stantly trampled. Thus, from a human point of view that focuses only on nature's sur­ face phenomena, the plantain community seems singularly unfortunate. If someone who felt sorry for the plantain com­ munity suddenly built a fence around it to keep walkers out, the plants would temporarily enjoy optimal conditions. Even before the component species could reach maximum growth, however, the more favorable environment would allow the growth of other kinds of plants that did not belong there, and these would grow faster. and larger than the plantain. In as little as six months, the component species of the plantain community would disappear from the spot, replaced by taller weeds such as fleabanes, alang­ alang grass, and ragweed (Ambrosia elatior). Progressives and Conservatives Civilization has developed by trying out various social sys­ tems. Even now, in many countries, the conflict continues between progressives who want to go on to the next, newest social system and conservatives who favor the status quo. Social change seems to occur when the existing system no longer provides an adequate livelihood for its members, who then start looking for a better system. As communities strive to enhance conditions favorable to their growth, however, after a certain point these same conditions, whose creation required so much time and sacrifice, start working against the community. The stage is then taken over by a new social system; in the case of plants, it is taken over by new plant communities better suited to the improved environment. Where an area has been denuded by volcanic eruptions or floods, the ground will never be occupied immediately by a

PROGRESSIVES AND CONSERVATIVES

121

terminal community, the community that is most stable and best suited to the climate and other natural conditions par­ ticular to that spot. For example, on Mount Mihara in the Izu Islands, or Mount Ontake on Sakurajima Island (off south­ ern Kyushu), the first plant communities to grow on new lava flows or piles of volcanic ash are composed of short­ lived herbaceous plants. Though the abundant precipitation of the rainy season (mainly in June) allows these plants to sprout, by August they have withered, not having grown sufficiently to survive the dryness of the hottest part of the summer. As these pioneer plants repeat their attempts to settle permanently on the harsh new land, their dead leaves and branches gradually mix with the weathered particles of lava to form the beginning of a soil. When enough soil has been formed, the pioneer commu­ nity should finally be able to take hold. Before this can hap­ pen, however, other plants that sprout more quickly and grow bigger take advantage of the improved substrate conditions and invade the spot. Then the next phase begins: the forma­ tion of a community of perennial herbaceous species. This community in turn strives to create environmental condi­ tions more favorable to its own growth. As the years pass, more fallen leaves and dead root material become mixed in, and the soil grows deeper and more fertile. By this time shrub species belonging to the third phase of the succession have already sprouted under the tall weeds. Though it appears that optimal soil conditions have been attained for the growth of the perennial herbaceous plants, the ground is already covered with the seedlings of spe­ cies belonging to the next phase, perhaps torch azalea (Rhododendron kaempferi), panicled hydrangea (Hydrangea paniculata), Roxburgh sumac, and Japanese green alder (Alnus firma). In the same way, seedlings of tall tree spe­ cies, such as light-tolerant, deciduous konara oak and light­ demanding Japanese red pine (Pinus densiflora), are also soon growing beneath the shrubs. And when these trees have grown up into a tall forest, under them one will be able to find seedlings of evergreen broadleaf trees, which indicate the

12 2 SUCCESSION AND SUBSTITUTE COMMUNITIES

direction of the next phase of succession. In areas near the coasts of southern and western Japan, these trees will include sudajii castanopsis (Castanopsis cuspidata var. sieboldii), tabunoki laurel, and Japanese camphor (Cinnamomum japonicum), each with dark-green, shade-tolerant evergreen (laurophyllous) leaves. Also included in the understorey will be evergreen holly (Ilex integra), Japanese fatsia (Fatsia japonica); and laurel-family shirodamo neolitsea (Neolitsea sericea). Farther inland the main trees will be several lauro­ phyll species of evergreen oak, with laurophyll wild camel­ lia (Camellia japonica) and hisakaki (Eurya japonica) in the understorey. Each new group of species arrives because the environ­ mental conditions, especially the soil, have been improved; each new species becomes established because it is more shade tolerant than the previous species and can grow up under their existing foliage. The evergreen broadleaf trees in the last stage are tall and have the dark green, shade-tol­ erant leaves that we call laurophylls. They constitute the last stage of succession because nothing else can grow up under their shade to replace them. Normally, a biological community appears outwardly to be flourishing at its high point, just when the seeds of the next succeeding community are sprouting within it. The point at which a plant community occurs and functions in its purest form is thus probably just before the environment has become optimal, when the community's component mem­ bers are still striving against difficult environmental odds to grow to their full potential. This corresponds to the time just before the community attains its fullest development. Among the plants existing at any given moment are those that may appear to be the strongest and continue to produce many new offspring, even though these are destined only to die before maturity and become soil for the next commu­ nity. When environmental conditions have been improved adequately, these bold plants suddenly lose their energy and begin to drop out before the next, more stable stage of the succession takes hold. Those species that were the most

HOW PLANT COMMUNITIES SUCCEED EACH OTHER

12 3

precocious elements of the former community usually do not constitute a major component of the new community. They either disappear as they mature or are pushed out to the periphery of the new forest, where there is more light and they may continue to protect the forest as members of its mantle community. The vicissitudes of plant communi­ ties are even harsher than those in human communities. When a new community comes into being, it turns out that the progressives cannot coexist with the new species that can then germinate, become established, and grow in the new environment.

How PLANT COMMUNITIES SUCCEED EACH OTHER

Other than the global recovery of climates and vegetation zones after the last ice age, which ended about fourteen thousand years ago, the earth has not experienced recent climatic changes great enough to alter fundamentally the distribution and development of plant life over wide geo­ graphic areas. Local processes, such as volcanic eruptions, floods, weathering of exposed rock, landslides, and the grad­ ual silting up of lakes and marshes with soil and organic matter, however, have created new environments or modified existing ones in ways that cause continuing changes in the vegetation. As we have seen, succession advances when underlying rock is weathered, the roughly broken-up products combine with organic materials to enhance the soil, and a leafy can­ opy shades the ground from the sun, resulting in changes in the local microenvironment. The particular sequence of stages in succession is called a sere. Soil conditions in marshes and lakes change gradually over long periods of time through accumulation of dead organic material from dying aquatic plants, such as dwarf water-lily (Nymphaea tetragonavar. angusta), Japanese spat­ terdock (Nuphar japonicum), and pond-weed (Potamogeton), or lakeshore vegetation, such as reeds (Phragmites), broad-

124 SUCCESSION AND SUBSTITUTE COMMUNITIES

leaved and narrow-leaved cattails (Typha), softstem bulrush (Scirpus tabernaemontani), and sedges like kasasuge (Carex dispalata) and okasasuge (Carex rhynchophysa). When these plants die, they contribute to the formation of soil, and the shoreline moves outward, eventually causing the marsh to become dry land. The succession that accompanies this drying out, proceeding from aquatic to submerged rooted vegetation, then to wetland and finally to dry land, is called a wet succession system; the corresponding sequence of particular communities is called a hydrosere. Similarly, on bare dry land, such as may become available after a landslide or on rock that has been spewed out dur1ng a volcanic eruption, plant growth furthers the formation of soil, which in turn provides for the growth of other plant species, and so on. This process of mutual development of plants and soil on dry land, from pioneer species to the ter­ minal plant community most suited to the local environ­ ment, is called a dry succession system; the corresponding sequence of particular communities is a xerosere. Pioneer Plant Species Both wet and dry succession systems involve at least some­ what regular changes. Plants that somehow manage to grow on new ground, where no others are growing, are called pioneer species. These are almost always what we might think of as weedy species; they produce small, light seeds, in very large numbers, which can be -dispersed very widely. Portulaca, for example, an annual weed that grows in agri­ cultural fields, produces a tiny seed weighing less than one­ hundredth of a gram�but each plant produces between 34,000 and 244,000 of them. Crabgrass, although it grows only from ten to thirty centimeters high, creates between 32,000 and 76,000 seeds per plant. Large trees such as oaks, which produce large seeds called acorns, make only a small number of seeds relative to the size of the tree. All plants, however, from small weedy

CLIMAX-THE END PRODUCT OF SUCCESSION

125

species to large trees, continually produce so many seeds that, if all of them germinated and grew to full size, an extensive area would be completely covered by the progeny of just one parent plant. But environmental conditions are harsh on most naturally formed bare ground, and normally only two or three kinds of plants can survive there. Most of the species that are the first to grow on newly bare ground have arrived there from another location in the form of seeds or spores. The pioneer species growing in any one place are the only plants that can tolerate the harsh environmental conditions. They are not innately pioneer species but rather are ordinarily found on forest edges, landslide areas, or in logged-over areas in the vicinity. All these species grow in habitats that are very different from those that would be physiologically optimal for them in the absence of their particular competitors. Recently created volcanic or other bare ground cannot support most types of plants, and it is the resulting absence of such competitors (combined, of course, with tolerance of the extreme physi­ cal conditions) that makes it possible for the pioneer species to colonize these areas. On newly bare ground, then, competition between plant species is not a decisive factor. Rather, it is the physical conditions of the site itself that determine which species can live there. The plants that make up the Arctic tundra and the herbaceous plants that grow in sparse, scattered desert communities are pioneer plant species. Uniquely, though, under these severe cli­ matic conditions of intense cold or aridity, they are at the same time plants of the terminal stage of succession. Climax-the End Product of Succession If local environmental conditions are relatively stable, plant communities (and wider biological societies that include animals) may eventually attain a state of equilibrium in har­ mony with their local conditions. The equilibrium is not necessarily static and may in fact be quite dynamic. Such

126 SUCCESSION AND SUBSTITUTE COMMUNITIES

communities persist as long as the environment does not change greatly-or as long as humans do not intervene to ruin their systems. This final stage of succession, the terminal community, is known as the climax. In the absence of major environmen­ tal change, the climax is normally the strongest form of bio­ logical society and is stable in the sense that its dynamic changes are constrained within limits. The vegetation of the climax stage is, in a sense, the botanical expression of the integrated local environmental conditions. Before humans started destroying nature and vegetation on a large scale, several thousand years ago, and in some places just a few hundred years ago, much of the earth's land sur­ face must have been covered by plant communities that were in or near some kind of climax stage. Each community was adapted and suited to its local climatic and other con­ ditions. Exceptions included areas that were recently or fre­ quently visited by natural disturbances, such as storms, landslides, or volcanic eruptions.

THE CLEMENTS SUCCESSION MODEL

Primary and Secondary Succession

Frederick Clements (1874-1945) was an American ecologist who described the process of succession and provided much of the terminology that we still use. He identified two basic kinds of succession. On sites that previously had no vegetation, such as the bare ground created by a lava flow, the sequence of plant groups that occupy the site is termed primary succession. On sites that previously had vegeta­ tion, such as abandoned agricultural fields, the sequence of plant communities that follows destruction of the former vegetation is termed secondary succession. One can also distinguish between natural succession, which occurs with­ out any human interference, and artificial succession, which

THE CLEMENTS SUCCESSION MODEL

12 7

occurs after human activity destroys a community that had perhaps attained a degree of stability. Because humans have intervened in nature in so many ways throughout the world, we can observe natural succes­ sion over larger areas only in polar and alpine regions, and on coastlines and volcanoes where new ground has been formed. Even in highly populated areas, however, we can see some phases of natural succession on certain kinds of smaller sites, such as sand dunes, cliffs, piles of gravel cre­ ated by landslides, and riverside terraces that are periodi­ cally flooded. After humans stop disturbing natural vegetation, we can observe secondary succession occurring everywhere, espe­ cially in populated areas, and perhaps with particular clarity on abandoned industrial or agricultural land. One example is the crop fields and rice paddies that have been cultivated for decades or even hundreds of years but have been abandoned, often due to poor economic returns or shortages of agricultural labor. Another example is the for­ ests of Japanese chestnut oak and konara oak that used to be harvested every fifteen to twenty-five years for charcoal but are no longer cut down (since modern society has shifted to petroleum-based fuels). Such secondary forests can be seen on the Kanta Plain of Pacific Japan, where they are under­ going succession toward the forests of evergreen shirakashi oak ( Quercus myrsinaefolia) that represent the terminal stage for that area. Nowadays, however, even if industrial, agricultural, or other kinds of land use stops, some other human activity soon commences, causing even more extensive destruction of plant life and natural landscapes. For this reason, although secondary succession can be observed everywhere, it almost never progresses to its final, stable stage. Instead, we see only mosaics of patches that represent various stages of trun­ cated succession. The distinction we make between natural and artificial succession is just an expedient to aid our understanding. In

12 8 SUCCESSION AND SUBSTITUTE COMMUNITIES

terms of the actual course of succession, it may not matter whether the process was initiated by a natural event or by human interference. The type of disturbance may or may not influence what kind of new plant community takes over. For example, it is sometimes difficult to discern whether a forest was logged or destroyed by an unusual storm just by looking at the kind of secondary vegetation that grows in afterward. In other cases, as many European ecologists have shown, the type of disturbance may be important if it greatly affects which species propagules are available in the first stages of succession. The most important thing about disturbance is its timing and frequency, whether it is a single, periodic, or continu­ ous disturbance. Even seemingly innocuous human actions, such as forest grazing, weeding, collecting fallen leaves, or trampling, can thoroughly alter the natural vegetation if they are repeated continuously over a long time. This can be seen in the way forest grazing in Europe converted former forest areas to steppe. On volcanic ash and lava, the primary succession process starts where there is no soil at all. The succession creates a certain soil condition, then the soil and other environmen­ tal conditions define the vegetation of the next phase, and the interaction between the vegetation and environmental con­ ditions continues. This process takes a long time, usually several centuries. In contrast, secondary succession occurs in places where soil already exists, such as abandoned agri­ cultural fields, and the course of succession is relatively rapid, often requiring less than a century and sometimes only a few decades to re-create a forest structure. Secondary succession is most rapid when the event that sets it off is a one-time occurrence, such as logging or physical damage caused by especially strong winds. Progressive, Retrogressive, and Deviant Succession

In many cases, succession may be diverted from its course toward a terminal community. For example, when disturb-

PROGRESSIVE, RETROGRESSIVE, AND DEVIANT SUCCESSION

129

ance such as forest grazing or cutting of underbrush contin­ ues over a long period of time, succession usually proceeds slowly. In some cases, the forest is replaced by non-forest vegetation, such as a grassy field, a bamboo stand, or brush­ wood. When plant succession is moving toward its potential ter­ minal stage, it is called progressive succession. If instead it goes in the other direction, this is called retrogressive suc­ cession. Normal progressive succession that is arrested at some point by some form of disturbance is no longer pro­ gressive and is not retrogressive; rather, it is called deviant succession (also called a plagiosere). The result is not a cli­ max stage but rather a disclimax community. Some of these aspects of succession are illustrated in figure 9. On the Kanta Plain, secondary succession on abandoned agricultural fields progresses through the following stages: weed communities of crowdipper (Pinellia ternata) and nishi­ kiso spurge (Euphorbia humifu:sa var. pseudochamaesyce), which normally grow in agricultural fields; taller fleabane communities (Erigeron canadensis and E. sumatrensis); tall grass communities containing short azuma-nezasa bamboo; a miscanthus grassland; a deciduous forest of Japanese chest­ nut oak and konara oak; and finally a climax forest domi­ nated by evergreen shirakashi oak. If the field is constantly trampled by people or animals, however, as occurs on path­ ways through fields or on athletic fields, deviant succession begins, no matter what stage the secondary succession has reached at the time the trampling begins. For example, on a path between agricultural fields, most plants disappear and the vegetation begins a course of devi­ ant succession toward a plantain community, composed only of the few species that can stand being constantly trampled. Similarly, a continuing periodic regime of mowing weeds, cutting underbrush, or pasturing livestock results in deviant succession toward a grassy community. And as long as someone walks on the path, puts livestock out to pasture, or cuts brush down to the ground more than once a month, the plantain or grassy communities will persist. As soon as the

Figure 9. The succession process Secondary Succession

Primary Succession

terminal community (climax)

i

��� successional community

·Vf

l :t:tW

retrogressive suc­ cession (caused by disturbance)

successional community

substitute vegetation

¥1 J

plant community of pioneer species

l

volcanic eruption

disturbance ceases

Primary succession occurs on new ground where there was no previ­ ous vegetation, such as on a new lava flow after a volcanic eruption. It proceeds from pioneer species through various successional communi­ ties to form a terminal community (climax) that cannot be displaced by other species unless there is some strong disturbance. In climates that have enough rainfall, the terminal community is usually a forest. Secon­ dary succession occurs after previous vegetation has been greatly dis­ turbed or destroyed, such as by a strong storm or by cutting to create agricultural fields. It may also begin with less drastic but continuing disturbance, such as repeated partial cutting for firewood, resulting in retrogressive succession to some kind of substitute vegetation. If this disturbance ceases, progressive succession toward the potential climax community may resume. In certain usually clearly defined cases, succes­ sion may be blocked and terminate in some kind of lasting community.

SUBSTITUTE VEGETATION

131

disturbance stops, though, succession immediately returns to its normal progressive course. The plantain community becomes a fleabane (Erigeron) community, and the grassy community becomes a community dominated by miscant­ hus grass (Miscanthus sinensis). Both subsequently undergo normal secondary succession, albeit at a slower pace if envi­ ronmental damage, such as soil compaction, has occurred in the meantime. Substitute Vegetation When the natural vegetation of a site is wiped out through some kind of disturbance, the vegetation that grows up in its place is called substitute vegetation, and the resulting plant community is called a substitute community. Sometimes we may wish to reclaim industrial or urban areas for new purposes where the natural vegetation has already been destroyed. To restore an appropriate vegetation cover, we must first understand the existing substitute plant communities, such as fleabane weed communities, second­ ary chestnut oak-konara oak coppice forests, or secondary red pine. Then we must also be able to determine the potential vegetation of the site, that is, what particular kind of natural vegetation the site could support if all human disturbance ceased. Nature Is a Beauty with Perfect Taste Nature is the world's greatest beauty. The German word for nature (die Natur) is a feminine noun, as was al?o its Latin predecessor natura. Nature has always worn her dress of green-plant life-in the style most appropriately suited to each location and season. In the lowlands of Japan, this means the deep green of evergreen broadleaf forests of cas­ tanopsis and evergreen oak species. In the mountains, the deciduous broadleaf forests of Siebold beech (Fagus crenata), mizunara oak ( Quercus crispula, formerly Q. mongolica var. grosseserrata), and daimyo oak ( Quercus dentata) change

13 2 SUCCESSION AND SUBSTITUTE COMMUNITIES

their dress with the four seasons, wearing pale new leaves in spring and bright colors in autumn. The subalpine areas of Honshu wear the dark green of certain fir species and north­ ern Japanese hemlock (Tsuga diversifolia), while in Hokkaido comparable coniferous forests take on the appearance of boreal forests of Yezo spruce (Picea jezoensis) and Sakhalin fir (Abies sachalinensis). The alpine belts are garbed in creep-· ing pine (Pinus pumila), and in summer, meadow flowers show the primary colors of red, yellow, and blue-violet. The evergreen castanopsis and oak forests of the lowlands, plains, and foothills are the original home of the Japanese people and the place where they continue to pursue their daily lives. Most of nature's green robe, its natural plant life, was obliterated hundreds of years ago. Similarly, dur­ ing the twentieth century, the original deciduous forests of mizunara oak and beech higher up in the mountains were also rapidly destroyed, cut down and replaced through a government policy of planting conifers on formerly forested sites, species such as cryptomeria (Cryptomeria japonica), Japanese cypress (Chamaecyparis obtusa), and Japanese larch (Larix kaempferi). The natural coniferous forests of the sub­ alpine belt also suffered great destruction as a result of the late twentieth-century burgeoning of tourism, and in partic­ ular the construction of tourist roads and related facilities. Even the alpine flowers, which hang on stubbornly through years or even decades of harsh conditions before they finally bloom, are being trampled or dug up by insensitive visitors. In this way, the beautiful, harmonious green robe of nature has been rapidly stripped away, from the seashores right up to the mountain summits. Nature, though, always tries to cover exposed bare ground and hastens to dress the bare patches with substitute vegetation, even if this clothing is temporary. Where bare dirt is exposed, as when large tracts of land are reclaimed from the sea, the first substitute vegetation that hurries to cover the area is usually composed of mantle species. If regular logging, burning, underbrush gathering, livestock pasturing, or other human disturbance persists for

EXISTING VEGETATION

13 3 .

decades or even centuries, however, a particular deviant kind of simple substitute vegetation takes over, one that is adapted to the recurring disturbance. What results is a con­ tinuing transitional phase of natural plant succession that persists as long as the recurring disturbance continues. When natural plant life is destroyed and substitute vegeta­ tion moves in to cover the bare spots, this does not mean that any plant can grow. The particular species that grow are those members of the natural flora that can tolerate the new conditions, plus a limited number of characteristic substitute plant species. Existing Vegetation

Most of the plant life we see around us is substitute vegeta­ tion that has grown up after the original vegetation of the area was destroyed by human activities. If you look at a map of the natural vegetation zones of Japan, you will see that the distribution of human population and vegetation zones is clearly correlated. As of 2003, Japan had sixty-five large cities with p,opulations greater than 300,000 people. Except for Sapporo and Asahikawa, in more recently settled Hokkaido, all these cities (and about 93 percent of the Japa­ nese population) are located in the evergreen broadleaf for­ est zone. But can we now actually observe any large evergreen broadleaf forests in Japan? The landscapes we see around us are made up of rice paddies, agricultural fields, aban­ doned farmland, roadside and other weed communities, miscanthus grass fields, nezasa and azuma-nezasa bamboo, and so on. There are also trees and forests, but most of these are deciduous oak forests, Japanese black pine at the coast, Japanese red pine inland, and cryptomeria and Japanese cypress in tree plantations. It is apparent that most of Japan's current existing vegetation, or actual vegetation, is plant life that grew in after the original vegetation, or at least the previous natural vegetation, was removed, over long peri­ ods of time.

Lasting Communities Among the various types of substitute vegetation, some represent "continuing" or "lasting" communities (Dauer­ gesellschaft in German) that may persist for long periods of time, even hundreds of years. Communities that we have mentioned already are good examples of this kind of deviant succession, such as the weed community that grows contin­ uously in agricultural fields that have been regularly weeded, cultivated, and fertilized over many years; and the plantain community that endures constant trampling on footpaths and athletic fields. Substitute vegetation becomes a lasting community when the site where it grows is exposed to regularly repeated dis­ turbance, usually by humans, that is consistently of the same type-be it logging, burning, pasturing of livestock, cultivat­ ing, trampling, or gathering underbrush for green manure. Such lasting communities, however, do not grow on vacant city lots that are used irregularly for various activities: for example, children playing there in the daytime, adults sneak­ ing in at night to dump garbage, someone lighting a bonfire or using it to park a car. This kind of irregular human dis­ turbance results in patchy mixtures of species from various substitute communities, such as roadside weed species, agricultural field weeds like crabgrass, meadow species like miscanthus or alang-alang grass, or mantle plants like kudzu. Exotic plants are usually incapable of penetrating stable natural forests that represent original plant communities. It is also difficult for exotics to invade those lasting communi­ ties that represent substitute vegetation adapted to regular disturbance regimes. Thus, exotic plants usually establish their first footholds in places such as vacant urban lots, where a sustainable balance between local environmental factors and plant life has not been attained. There can be exceptions, especially if there is recurring disturbance or there are available "open niches" that newly arrived species can exploit. In the case of forests, one example is the dra­ matic invasion by the Chinese shrub Ligustrum sinense

VANISHING NATIVE VEGETATION

13 5

(Chinese privet) into the previously largely shrub-free flood­ plain forests of the southeastern United States during the twentieth century. The lasting substitute communities of Japan have adapted and endured in the context of regular human impact, evolv­ ing into the semi-natural landscapes that are part of the cul­ ture and heritage of the Japanese people. The plant life of the fields, hills, and farms that make up the Japanese image of homeland includes the red pine, chestnut oak and konara oak woodlands, meadow grasses such as miscanthus, Japa­ nese lawn grass and alang-alang, and the other plant life of the agricultural fields, rice paddies, and streams. Vanishing Native Vegetation As we have seen, most of the plant life growing in the fields and on mountain slopes represents either temporary or sub­ stitute vegetation that has endured various types of human impact over the course of hundreds or even thousands of years. Vegetation that has yet to be affected by humans is referred to as original vegetation. Humans began to have a significantly greater effect on plant life than other animals only during the last twelve thousand years or perhaps even less. The destruction of the original vegetation has occurred at different times in different places. Under the severe con­ ditions of alpine and polar regions, the original vegetation remained intact longer. In the tropical, subtropical, and temperate zones, however, including Japan and Europe, coastal lowlands, hillsides, and low mountains near lakes and marshes in particular have long been subject to human impacts. After the end of the last glacial epoch, climates warmed and the pattern of major natural vegetation and landscape types across the earth reached more or less its current con­ figuration (shown in map 1) by about six to eight thousand years ago. In Japan, where glacial effects had been compara­ tively minor, the whole country, from seacoasts to high mountains and from Okinawa to Hokkaido, was almost

13 6 SUCCESSION AND SUBSTITUTE COMMUNITIES

completely covered with original vegetation up until sev­ eral thousand years ago. Except for places where trees could not grow well, such as continually shifting sand dunes and beaches, periodically flooded tidal wetlands, and areas where temperatures are too low, winds too strong, or landslides too common, the whole country was covered with old­ growth forests particularly suited to each location. In Kyushu, Shikoku, and lowland Honshu south and west of Tokyo, as well as around Sendai on the Pacific coast north of Tokyo, even in hilly areas and low mountains, the domi­ nant forests were the evergreen broadleaf forests composed of species such as sudajii castanopsis, tabunoki laurel, ichii­ gashi oak ( Quercus gilva), shirakashi oak, urajirogashi oak (Quercus salicina), wild camellia, evergreen holly, and so on. As can be seen by observing remnant forests near the ruins of the capital of the Asuka era (593-710), near Nara, this for­ est zone has been inhabited by people since ancient times and was the first to suffer the degradation of its original veg­ etation. The lowlands of Hokkaido and northern Honshu, and the upland and mountain regions of Kyushu, Shikoku, and Hon­ shu, were originally covered by deciduous broadleaf forests made up primarily of species such as beech (Fogus crenata or F. japonica), mizunara oak, daimyo oak, and species of maple (Acer). The original vegetation of these areas was rap­ idly destroyed during the twentieth century. The Japanese Alps and Mount Fuji, at altitudes between 1,600 and 2,400 meters, used to be covered with subalpine conifer forests of Veitch's silver fir (Abies veitchii) and Maries' fir (Abies mariesii). The mountains in Hokkaido were covered with subalpine conifer forests of Yezo spruce and Sakhalin fir, in northeastern Hokkaido these extended right down to the shoreline. At and above the tree line, that is, above the subalpine coni­ fer forests, grew high-mountain plant communities of creep­ ing pines and alpine dwarf-shrubs and flowering herbs. The creeping pine also occurs in Siberia, where it grows taller,

NATURAL VEGETATION

137

but its stunted form is especially characteristic of tree line in Japan. The subalpine and northern conifer forests, as well as the alpine vegetation, have begun to suffer the effects of human activity only very recently. Evergreen broadleaf forests have been converted to and maintained as substitute vegetation for such a long time in many areas that it is no longer possible to determine pre­ cisely what the original vegetation's composition and struc­ ture were. And in recent decades, industrial development has even begun to change the fundamental physical condi­ tions of habitats in many places. Remnant areas of original vegetation, however, can be confirmed in the subalpine conifer forest and in the alpine belt. Natural Vegetation If we define original vegetation as that which has been totally unaffected by human activity, we are forced to say that original vegetation is now limited to exceedingly few areas in the world. In the evergreen broadleaf forest zone of Japan, there are remnants on steep slopes rising from the sea and on hillsides around Shinto shrines or Buddhist temples, though sometimes the forest in these latter places is vegetation that has recovered or has been restored to locally appropriate evergreen broadleaf forest but really cannot be called either substitute or original vegetation. What term do we use to describe this kind of plant life? When the vegetation of a site has been destroyed, as by human activity, but locally appropriate vegetation has returned, or when the combination of species is very close to the original vegetation in spite of some human impact, we call this natural vegetation. As long as the plant com­ munity is composed of the appropriate fundamental spe­ cies, even though it may have sustained a certain level of human disturbance in either the near or distant past, it qualifies as natural vegetation. Thus some kinds of mature secondary vegetation can also be natural vegetation. The

13 8 SUCCESSION AND SUBSTITUTE COMMUNITIES

definitions of original vegetation, natural vegetation, and substitute vegetation have slightly different nuances for dif­ ferent experts. Potential Natural Vegetation

If some day all human interference in nature suddenly stopped, what kind of natural vegetation might a site poten­ tially be able to sustain? Over time, through repeated proc­ esses of succession, appropriate vegetation almost identical to the original vegetation might eventually be restored-if the physical conditions of the site, such as soil texture and depth, had not been altered. If site conditions had been altered, for example through soil erosion, then a different type of stable vegetation would eventually arise. In either case, the termi­ nal vegetation that would arise after disturbance ceased is what we call potential natural vegetation. Most of the substitute vegetation in Japan represents last­ ing communities maintained by cultivation and other regu­ lar human activities, such as logging, weeding, and burning. We can assume that at least several centuries have elapsed since the original vegetation at these sites was destroyed. During this time, however, many of the sites themselves have also been altered; for example, mountain slopes have been broken up for terrace farming of vegetables, or long years of fertilization and cultivation have resulted in the soil becoming unnaturally high in nutrients. Consider Ise and Shima on the Kii Peninsula of Pacific southern Honshu, and the islands and shorelines of Japan's Inland Sea. These regions were originally home to forests of castanopsis and other evergreen broadleaf trees growing on low-fertility soils derived from granite and fossil-bearing rocks of the Paleozoic era. During the twentieth century these areas were encroached upon by humans, starting with the establishment of saltworks and then smelters, in addi­ tion to repeated logging for firewood, charcoal, and rafts for culturing pearl-bearing oysters. As a result, soil erosion has

POTENTIAL NATURAL VEGETATION

13 9

been extreme, and now only sparse forests of Japanese red pine can grow in these areas. At Ise and Shima there are coastal areas that look just like British heaths, covered with urajiro fern ( Gleichenia japonica) and scrambling fern (Dicranopteris pedata), and azalea-related heath-family shrubs like shashambo blueberry (Vaccinium bracteatum). On some islands in the Inland Sea, even red pine .can no longer grow and many of the hilltops are completely bare. In such areas, which are prone to dryness and where the soil has been eroded and fertility lost, even if human inter­ ference ceases completely, the potential of the site to sup­ port the kind of evergreen broadleaf forest that once grew there is greatly diminished. The only potential natural veg­ etation for such sites now is often red pine. When we try to restore a forest by planting trees that best suit the soil and other environmental conditions of a partic­ ular site, such as in industrial areas or other "wastelands," the trees do not always succeed in taking root. For example, we may have determined that a forest of castanopsis was the original vegetation on the bare mountains of islands in the Inland Sea, and at Ise and Shima, where the· current vegetation is only sparse groves of red pine. Even so, there is no guarantee that planting the component species of the castanopsis forest will be successful. In and around the urban and industrial areas of modern Japan, violent human assaults not only have torn away the natural vegetation but have also greatly changed the physical · conditions of large areas, for instance, by paving, tearing up the topsoil, and converting sites to landfills. In the process of land-use planning, urban renewal, road and factory con­ struction, and other industrial land usage, the most impor­ tant consideration is how to regenerate the vegetation that once grew on the site. Planners often employ the simplistic solution of planting exotic species or planting saplings of just one kind of tree, in order to produce some kind of "greenery." In order actually to restore self-maintaining local nature, however, planners must go beyond both the existing

140 SUCCESSION AND SUBSTITUTE COMMUNITIES

vegetation and the original vegetation; they must determine what type of natural vegetation the site can support now. In other words, what is the potential natural vegetation? It is important to remember that in the formation of a last­ ing community, only a certain number of substitute plant spe­ cies can tolerate the conditions represented by each type of potential natural vegetation. For example, mandarin orange trees can be maintained as substitute vegetation only where the potential natural vegetation is castanopsis forest. Groves of moso bamboo (Phyllostachys pubescens) will grow only in regions where the potential natural vegetation is ever­ green broadleaf forest, such as castanopsis or evergreen oak. Apple trees can persist as lasting communities only in deciduous broadleaf forest regions that are classified as belonging to the beech-forest zone. To take an extreme example, unless enormous amounts of money are spent on greenhouse facilities, rice and banana plants will never grow sustainably in the alpine creeping-pine belt, no matter what human management is applied. If lawns, hedges, and rows of trees are not planted in keeping with the potential natural vegetation of the site, they will not last long either, no matter how much money we spend or how strong our expectations are. It is also difficult for such "greenery" to form a plant landscape that genuinely suits the natural sur­ roundings and never becomes uninteresting. The Relation between Substitute and Potential Natural Vegetation

The evergreen broadleaf forest zone dominated by cas­ tanopsis and evergreen oak is where the Japanese originated as a people and where most Japanese still live today. One particularly representative species of this forest zone is the wild camellia, so this kind of forest has come to be called wild camellia-type forest (or Camellietea japonicae in phy­ tosociological terminology). The original vegetation of this zone has experienced human impact for several thousand years, so it has been replaced by various types of substitute

SUBSTITUTE AND POTENTIAL NATURAL VEGETATION

141

vegetation, as happened also in China and southernmost Korea. Human destruction of natural wild camellia-type forests began long before such things were studied and recorded. This can be surmised from the fact that there are few depic­ tions of landscapes featuring the evergreen broadleaf forest in Japanese paintings of the Azuchi-Momoyama period (15681600) or the Edo period (1600-1868), such as the wood­ block prints of the "Fifty-three Stations of the Tokaido" (the Pacific-coast route between Tokyo and Kyoto). In those prints, low mountains are occupied byJapanese red pine and shorelines by Japanese black pine (Pinus thunbergii), and the only depictions of something close to natural vegetation areJapanese fir trees shown on high mountain ridges, where they have managed to hang on even down to the present. In the Meiji era (1868-1912), written and spokenJapanese were quite different, including the ways in which people expressed their feelings. In his writings, Doppo Kunikida tried to express what was "natural" to people at that time by inventing a new writing style that permitted people to describe nature without formal restrictions. As a result, he is often considered a pioneer of "naturalism" in Japanese lit­ erature, though he himself was not a naturalist. In his novel Musashino, published in 1898, he described the mixed forests of Japanese chestnut oak and konara oak of the Kanta Plain, the red-pine groves of the mountains in west­ ern Honshu, and miscanthus (Miscanthus sinensis) commu­ nities of Kanta (which also contained the azuma-nezasa bamboo Pleioblastus chino var. chino) and of Kansai (west­ ernJapan; which contained the nezasa bamboo Pleioblastus chino var. viridis). These are all substitute vegetation types that had survived under regular human activities, but because they were the first types of nature depicted in liter­ ature, the Japanese thought until recently that they were the natural landscapes ofJapan. Production of chemical fertilizers in Japan also began in the Meiji period. After World War II, powerful, organic, chlorinated insecticides like DDT and herbicides like 24-D

142 SUCCESSION AND SUBSTITUTE COMMUNITIES

were introduced, and the production and use of chemicals, including poisons such as organic mercury and arsenic, have continued at high levels. Combined with the inven­ tion and widespread use of construction equipment such as bulldozers, these developments have not only devastated natural plant life and landscapes over large areas but have also thoroughly altered the topography at many places. The result has been the formation of types of environments that are completely different from those that existed there in the past. Qualitative and quantitative impoverishment of the liv­ ing communities has accelerated these changes, and accord­ ingly, new types of substitute vegetation are forming. In general, keeping in mind that the potential natural veg­ etation is not always the original vegetation due to environ­ mental changes, we can say the following about potential natural vegetation for the various zones of substitute vegeta­ tion in Japan. On the Kanta Plain and plateau, where the soil still contains a thick layer of loam, the current potential natural vegetation would mostly be evergreen broadleaf for­ est of shirakashi oak, which is thought to be the original vegetation of such areas. From the Kii Peninsula of south­ central Honshu west to Kyushu, the potential natural vege­ tation of areas with thick layers of well-drained flatland and plateau topsoil is thought to be evergreen forest of ichiigashi oak, as long as the physical habitat has not been severely damaged. In regions where topsoil is relatively thin and tends to dry out easily, particularly on inland mountainsides and other such areas at altitudes below 700 meters, forests of ura­ jirogashi oak or other evergreen oaks are thought to be the main potential natural vegetation. Along coastlines, forests of sudajii castanopsis or tabunoki laurel may still be the potential natural vegetation. For the Kanta area, the poten­ tial natural vegetation and corresponding actual vegetation are depicted in figure 10. When we understand the relationship between the poten­ tial natural vegetation and substitute vegetation for a par­ ticular site, we can learn what kind of human-induced conditions produced the substitute vegetation and how the

POTENTIAL NATURAL VEGETATION ACTS LIKE A MIRROR

14 3

vegetation has developed and maintained its current form under such conditions. By looking at the vegetation, we can also identify what kind of human actions are currently affecting the vegetation or habitat. We can also discern what is required to bring about the natural regeneration of a site toward its potential natural vegetation. All the substitute vegetation that we see around us is like clothing and makeup applied to the bare ground. Human actions-rapid, recent, and massive-not only have stripped the ground bare of its most appropriate natural or semi­ natural covering but have often gone so far as to gouge and scar the very earth underneath, resulting in the wretched appearance of the surface in many places. The substitute vegetation that has covered the ground after the effects of human avarice is often inappropriate to the site and its soil; it can even exacerbate the damage by causing the soil to degenerate, or produce uniform plant communities due to a temporary excess of nitrogen. Potential Natural Vegetation Acts like a Mirror Potential natural vegetation is sustained by and thus reflects the sum total of environmental factors affecting a site. Thus, as a model for future development, conservation, and resto­ ration of nature, we must leave in place representative examples of natural vegetation that continue to express the original biological and ecological character of each locality. We must also strive to restore to their original state those biological types that have already been lost. Of course, if all that we want from plants is organic prod­ ucts, shade, or rows of street trees, then any number of spe­ cies can substitute for the natural vegetation. The exotic spe­ cies of grasses that are planted nowadays on slopes flanking expressways or the imported tulip poplars (Liriodendron), sycamores (Platamzs), or deodar cedar (Cedrus deodara) trees planted along roadsides should suffice as tolerable substi­ tute vegetation for the potential natural vegetation in each place, as long as growth can be sustained.

Figure 10. Potential and actual vegetation in Kanto Plain potential natural vegetation

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