Forest as a Health Resource (essentials) 365842527X, 9783658425272

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Joachim Rathmann

Forest as a Health Resource

essentials

Springer essentials

Springer essentials provide up-to-date knowledge in a concentrated form. They aim to deliver the essence of what counts as “state-of-the-art” in the current academic discussion or in practice. With their quick, uncomplicated and comprehensible information, essentials provide: • an introduction to a current issue within your field of expertise • an introduction to a new topic of interest • an insight, in order to be able to join in the discussion on a particular topic Available in electronic and printed format, the books present expert knowledge from Springer specialist authors in a compact form. They are particularly suitable for use as eBooks on tablet PCs, eBook readers and smartphones. Springer essentials form modules of knowledge from the areas economics, social sciences and humanities, technology and natural sciences, as well as from medicine, psychology and health professions, written by renowned Springer-authors across many disciplines.

Joachim Rathmann

Forest as a Health Resource

Joachim Rathmann Augsburg, Germany

ISSN 2197-6708 ISSN 2197-6716 (electronic) essentials ISSN 2731-3107 ISSN 2731-3115 (electronic) Springer essentials ISBN 978-3-658-42527-2 ISBN 978-3-658-42528-9 (eBook) https://doi.org/10.1007/978-3-658-42528-9 This book is a translation of the original German edition “Gesundheitsressource Wald” by Rathmann, Joachim, published by Springer Fachmedien Wiesbaden GmbH in 2023. The translation was done with the help of an artificial intelligence machine translation tool. A subsequent human revision was done primarily in terms of content, so that the book will read stylistically differently from a conventional translation. Springer Nature works continuously to further the development of tools for the production of books and on the related technologies to support the authors. Translation from the German language edition: “Gesundheitsressource Wald” by Joachim Rathmann, © Der/die Herausgeber bzw. der/die Autor(en), exklusiv lizenziert an Springer Fachmedien Wiesbaden GmbH, ein Teil von Springer Nature 2023. Published by Springer Fachmedien Wiesbaden. All Rights Reserved. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Fachmedien Wiesbaden GmbH, part of Springer Nature. The registered company address is: Abraham-Lincoln-Str. 46, 65189 Wiesbaden, Germany

What you can find in this essential

• • • • • • •

A brief introduction to various forest ecosystem services A concise presentation on forest romance and forest solitude A characteristic of affective and emotional human-place relationships A sketchy presentation on forest climate A differentiated explanation of how forests act as a health resource Shinrin Yoku: Forest Bathing Forests in climate change

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Preface

The lush green of a summery mixed forest, the play of light in the canopy, the tapping of the woodpecker, the fresh forest air; all these are factors that can contribute to relaxation and recovery. A walk in the forest is an excellent way to switch off from everyday life and recharge. Numerous positive health aspects can be associated with a walk in the forest, as even movement as such prevents numerous diseases. The risk of arteriosclerosis decreases, which in turn reduces the associated risk of a heart attack or stroke. The forest climate with increased humidity, reduced temperatures, and a lower air hygiene load has a positive effect on the human organism, as do essential fragrances found in forests. Under the keyword “forest bathing”, there has been a strong popularization of forest visits for preventive health effects. The following will briefly outline which aspects can be scientifically proven to what extent. Parts of the text are based on the book chapter “Forest Therapy” 2022. In: Forest in the Diversity of Possible Perspectives, Eds. K. Berr and C. Jenal, 299– 318, Wiesbaden: Springer VS, which can be reused here with the kind permission of Springer Publishing. Augsburg, Germany

Joachim Rathmann

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Contents

1 Introduction: Forests as a Recreation Area . . . . . . . . . . . . . . . . . . . . . . . 1.1 Ecosystem Services of Forests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Forest Solitude: Forests as Places of Longing . . . . . . . . . . . . . . . . .

1 3 5

2 The Health Benefits of Forest Visits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Forests: Places of Spiritual Refuge and Encounter . . . . . . . . . . . . . 2.2 Human-Place Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Forest Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9 11 16 18

3 Shinrin Yoku: Forest Bathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Multisensory Forest Experience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Mindfulness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Effects on the Human Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21 22 23 24

4 Forests in Climate Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

27

5 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

29

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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About the Author

Joachim Rathmann teaches and researches as a private lecturer on humanenvironment relationships at the Institute for Geography at the University of Augsburg. He is an Adjunct Professor at the School of Science and the Environment at Memorial University (Newfoundland, Canada). He received his doctorate on climate changes in southern hemisphere Africa, and his habilitation was on ecosystem services.

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Introduction: Forests as a Recreation Area

The forests of Central Europe have had a long and varied history since they were able to spread after the end of the last Ice Age. In addition to long-term natural climate changes to which forests adapt, they are characterized by millennia of use, which has profoundly affected the forest ecosystem and its composition. Globally, forests have been affected by massive changes for many decades due to deforestation, anthropogenically enhanced climate change, and the associated loss of biodiversity. Forests are large carbon sinks, influence regional and global climate, and are ecosystems in which numerous organisms interact in complex ways. Additionally, forests provide the living and habitat of indigenous and also isolated, uncontacted peoples. This primarily applies to tropical rainforests and underscores the importance of protecting these forest areas not only because of their high biodiversity and importance for the global climate system, but also to protect the people living there in their traditional culture. About a third of Germany’s land area is covered by forest. This highlights the great importance of forest ecosystems as a landscape space but also as a utility space for humans. Until the Middle Ages, natural forest areas dominated large parts of Central Europe, in the 17th century there were large-scale clearings, followed by a romantic transfiguration of the German forest as a place of longing. In the 1980s, forest dieback dominated the environmental discourse. Currently, forests are being severely damaged by extreme climatic events. Because the global temperature rise, the change in precipitation distribution, and especially the increase in climatic extreme events (droughts, heatwaves, late frost events, storms, heavy rain)—both in number and intensity—have negative effects on forest ecosystem services. The hot and dry summers of 2018 and 2019 have already

© The Author(s), under exclusive license to Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2023 J. Rathmann, Forest as a Health Resource, Springer essentials, https://doi.org/10.1007/978-3-658-42528-9_1

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Introduction: Forests as a Recreation Area

led to massive forest damage in Central Europe. Such events could become more frequent in the future. At the same time, forests, because they store large amounts of carbon dioxide, are globally celebrated as “climate saviors” and regionally as “medicine” for stressed city dwellers. This alone shows that forests fulfill very different functions; they are an important economic factor, habitat for numerous organisms, recreational areas for humans, a sink for greenhouse gases, they regulate the local climate and water balance, provide protection against avalanches, protect against noise and filter pollutants from the air. Currently, forests are once again experiencing a strong positive attribution of meaning: forests as climate protectors and forests as spaces for sports, recreation, and health are examples of this. Forests as a health resource have now become a topic that is increasingly being discussed in large parts of society as well as in politics and is finding its way into legislation. Based on the State Forest Act (LWaldG, in the version of the announcement of July 27, 2011), the first recreational, healing, and spa forests were named in Mecklenburg-Western Pomerania. In § 22 it is regulated that corresponding forest areas are to be “protected, maintained or designed for the purposes of recreation” if “the welfare of the general public requires it” (LWaldG § 22 (1)). This applies in particular to forests in conurbation areas and those “near spas, health resorts, and recreational areas” (LWaldG § 22 (2)). The trend towards an increased use of forest therapy in health promotion is also emerging in other federal states. However, the actual definition of “forest” remains unclear, as the state laws offer different definitions. The Federal Forest Act (BWaldG § 2) sees the forest as a “land area stocked with forest plants”. This corresponds to the so-called “timber soil” in the classification of forest operational areas. Forest areas in the sense of the BWaldG also include clearings and forest paths as so-called “non-timber soil” in the forestry category. In contrast to parks, botanically speaking, the forest is a vegetation form dominated by trees with an extent large enough for its own forest climate to develop. A grove does not correspond to a forest according to these definitions, but in everyday understanding, it does at least to a small forest. Forests as recreational spaces have experienced a strong popularization in the public in recent years; especially under the keywords forest bathing and forest therapy, the field is served by numerous popular science books. The content spectrum ranges from alternative medicine, esoteric approaches to various spiritual and ethnic directions of thought. Economic interests are also tied to this, which can be reflected in seminars, brochures, book publications or generally also in nature tourism. At the same time, there is an increasing interest in scientifically analyzing and quantifying the health benefits of forest visits in order to establish

1.1 Ecosystem Services of Forests

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different evidence-based offers for various forms of forest therapy based on this (detailed on forest therapy: Schuh and Immich 2019; Rajoo et al. 2020), because numerous scientific findings show positive health effects through forest visits, which can increasingly be quantified (Grilli and Sacchelli 2020).

1.1

Ecosystem Services of Forests

Forests are not simply pure tree stands, even if some spruce forests give this impression, they are rather complex ecosystems that are based on the interaction of all organisms. The symbiotic relationship between fungi and tree roots has been known for a long time; these mycorrhizae could also help to connect individual trees through underground material flow bridges. The direct interactions between individual trees can go so far that the root systems also grow together, so that an exchange of substances between different tree individuals is possible (cf. Matyssek et al. 2010, 304 f.). Therefore, it is sometimes discussed whether such a forest stand can not be referred to as a “super-organism”. Forests have different “forestry forest functions” that are also used accordingly for forest function mappings. Overall, the forests are then classified into a use, protection, and recreation function. The Commercial Forest • • • • •

Timber yield as a raw material base for the wood and paper industry Energy production Hunting industry Basis for the income of forest owners Provision of jobs, especially in structurally weak rural areas

The Protective Forest • • • • • • • •

Regulation of the water balance, securing the drinking water supply Soil protection, protection against erosion Protection against rock and snow avalanches Balancing climate effect, air purification Climate protection through CO2 binding in biomass but also in dead wood Noise and emission protection Visual protection, impact on the landscape Species and habitat protection

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Introduction: Forests as a Recreation Area

The Recreational Forest • Tourism • Recreation is often the most significant forest function in forests near cities • Various activities such as walking dogs, strolling, jogging, cycling, horse riding, mountain biking • Usage conflicts These classic forest functions can also be found in the concept of ecosystem services. This concept describes the benefits that people can derive from ecosystems and attempts to monetize them. Natural ecosystems can positively affect human well-being in many ways. Such interconnections of ecological and social systems have been described and studied in recent years with the concept of ecosystem services. “Services”, which nature provides to humans free of charge, are monetized to create awareness of the value of ecosystems in politics and society. This can lead to additional arguments for nature conservation. Nature should then also be protected as a basis for human health. Because in ecosystems, various abiotic and biotic elements are closely intertwined, so that any human intervention changes these and thus also changes the coupling of ecosystems to social systems. The underlying idea is that human well-being is connected in many ways to the state of global ecosystems. The Millennium Ecosystem Assessment (MEA) provided a detailed description of the state of global ecosystems in 2005; ecosystem services were divided into four classes: • Provisioning Services (e.g., production of food, fodder, provision of drinking water) • Regulating Services (e.g., pollutant filtering by soils, storage of greenhouse gases, protection against flooding) • Cultural Services (e.g., recreation, religious and spiritual values) • Supporting Services (e.g., photosynthesis, soil formation) Forests provide numerous ecosystem services for the survival, well-being, and maintenance and strengthening of human health. Forests offer recreational spaces that can positively stimulate all senses, which can therefore be seen as a resource that affects both physical, mental, and social aspects of health. In forest areas located near urban areas, the recreational function is often the most important forest function. Forests are used for numerous recreational activities; be it hiking, walking, dog walking, nature observations, or collecting berries and mushrooms. For further

1.2 Forest Solitude: Forests as Places of Longing

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recreational behavior such as horse riding, jogging, walking, cycling, mountain biking, or geocaching, forests provide a welcome backdrop, with electromobility in cycling having significantly expanded the spatial usage radii. This multiple usage and recreational behavior often involves target conflicts that frequently occur in heavily frequented forests. There has been a strong increase in demand for health-relevant forest visits, be it in health tourism or through therapeutic offers in the context of “forest bathing” (Ihlow and Lamminger 2020; Schuh and Immich 2019). Climate changes mean that urban forests in particular are becoming increasingly important as recreational spaces. Compared to urban heat islands, forests offer a directly perceptible balance and thus a preventive health effect. With the first plenary session in 2013, the UN organization of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) or World Biodiversity Council has established itself for scientific policy advice to protect ecosystem services and the Earth’s biological diversity sustainably. Here too, a close interconnection between ecosystem protection and human health is shown: A decline in ecosystem services can restrict people’s quality of life and many ecosystem services are hardly or not at all replaceable, which can result in their loss having high economic costs. An economic perspective opens up the view for the value of such services and can put them in relation to each other. Some of these services, such as recreation, are available free of charge as public goods and are not subject to a price mechanism. To include these services in a price mechanism, hypothetical markets must be generated. This can be done by asking for a certain willingness to pay. The recreational service of forests in Germany can thus be calculated at almost 30 e per person per year for forests in the local area. If this value is extrapolated to the whole of Germany, the recreational value of the forests amounts to 2.4 billion e per year (Elsasser et al. 2021). For society, the “provision” of the ecosystem service “recreation”, which is accessible to everyone, is associated with a high profit. The additional health benefits are not even included in this.

1.2

Forest Solitude: Forests as Places of Longing

Historically, forests have undergone many changes in human perception and attribution of meaning. For the Romans, the dark forests of Germania were terrifying, and even in the Middle Ages, forests were often still spaces where the wild, the outcasts, hermits, saints, or lovers lived (Harrison 1992, p. 81 f.).

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Introduction: Forests as a Recreation Area

The Roman historian Publius Cornelius Tacitus described the dark forests of Germania in his slim work Germania in 100 AD. The depiction of the Germanic tribes in their wild habitat and the fear of staying in certain parts there can be read as a counter-design to Roman civilization. At the same time, a myth of the terrifying forest, in which evil spirits wreak havoc, was established (Tacitus 2012). The dense, dark forest was also the protection that helped the Germans keep the Romans at bay (Fig. 1.1). In German cultural history and literature, forests often have a very ambivalent meaning: On the one hand, they are places where evil spirits hide or evil spirits frighten the wanderer in the dark tree labyrinth. At the same time, forests appear as lovable places of longing for lovers or dreamers seeking solitude. These two sides of the lovely and the terrifying provide the backdrop for numerous fairy tales and legends. In Grimm’s fairy tales, forests can often be described as a place of transformation—“uncanny enchantment” (Harrison 1992, p. 203). The witch living in the forest in Hansel and Gretel meets a bad end, but not the siblings, who can lead a good life free from poverty and hunger after their stay in the forest. Little Red Riding Hood, who visits her grandmother living in

Fig. 1.1 The perception of forests is tied to individual attributions of meaning and symbolic charges. (Bavarian Forest, Photo: © Rathmann)

1.2 Forest Solitude: Forests as Places of Longing

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the forest, encounters the evil wolf on the way, but the fairy tale ends well for her; not for the wolf, the forest dweller, who dies. An old donkey, who is to be slaughtered, meets three other old animals, a dog, a cat, and a rooster. The Bremen Town Musicians want to spend the night in a robbers’ house in the forest, but first they have to outwit and chase away the evil robbers and can then start a new life in this house in the forest. Snow White also finds refuge in the forest. These examples show a typical ambivalence attributed to the forest; it appears threatening, but can lead to something completely new, to a transformation for the better. The increasingly positive connotations that forests experience are then shown in Romanticism, where the German forest is described as an elevated landscape of longing in poems and stories (for more details: Jenal 2019, Chap. 3). Since Romanticism, forests have been seen as places of freedom as a counterpoint to the alienation processes of modern, urban lifestyles. This positive connotation of forest visits is also evident in the context of “forest solitude”. Forest solitude describes a voluntarily chosen solitude in a forest environment, often a religiously motivated ascetic ideal of life, which was already evident long before Romanticism in a religious context. In Hinduism, it is the Sadhu, the wandering monk, who seeks an ascetic life also in the forest; Buddhism has a comparable tradition, such as in the Thai forest tradition. Christian monks in Europe sought refuge in the seclusion of forests as hermits and eremites until the late Middle Ages, which, away from the hustle and bustle of the city, invite for contemplation and meditation. In German Romanticism, the topos of solitude in the forest was illuminated as a literary motif. Ludwig Tieck (1773–1853) clearly shows the romantic exaggeration of the idyllic ideal of solitude in the forest: Solitude in the forest, That delights me, As much in the morning as today In eternal time, Oh how it delights me Solitude in the forest. Solitude in the forest How far you lie! Oh, you will regret Once with time. Oh, only joy Solitude in the forest!

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Introduction: Forests as a Recreation Area

Solitude in the forest Delights me again, No harm befalls me, Here lives no envy Delights me anew Solitude in the forest. (Tieck 1995, p. 533).

With the key concept of solitude in the forest, individual emotional sensations merge with an impression of nature that is gained in forests. It is the image of a fairy-tale-like connection between man and nature in a positive sense. This implicitly emphasizes the importance of forests for human well-being. For American Transcendentalism, for example, Ralph Waldo Emerson (1803–1882) shows this importance in his poem with the German title “Waldeinsamkeit”: “Cities of mortals woe begone Fantastic care derides, But in the serious landscape lone Stern benefit abides.” (Emerson 1858).

The positive charge of forests as places of longing, as recreational and retreat spaces corresponds to a strong idealization of nature, which currently finds a certain echo in a popularized form of forest bathing.

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The Health Benefits of Forest Visits

In addition to wood production and other ecosystem services, urban forests in particular serve for recreation and thus also for health promotion. Therefore, there is a right of free access to forests, regardless of the type of ownership, for the purpose of recreation (BWaldG § 14). Visits to the forest thus become a kind of free health prevention; this implicitly also takes into account the promotion of health for low-income groups. Urban forests have a special significance as a recreational area for urban residents. Recreation, regeneration, or re-creation refers to the recovery of expended energy and the restoration of physical and/or mental performance. It is thus a process that seeks to regain psychological and physical activation. This describes a process in which an organism regenerates and gathers new strength after physical or mental fatigue, after an injury or illness, through a rest phase. Recreation thus has a compensatory and at the same time preventive effect; if it is absent, diseases can occur. For recreation to succeed, a distancing from the current stress situation is first necessary so that attention can be directed to the recovery phase or activity (Allmer 1996). Once the activation level has dropped, the regeneration of exhausted resources can begin. The ensuing physical and psychological relaxation enables stress reduction and emotional balance. At the end of the regeneration phase, the energy for the upcoming challenge can be re-bundled and oriented accordingly. Spending time in green spaces, in natural landscapes, city parks or forests can increase individual well-being in various ways, enable recreation and thus promote, strengthen and stabilize health (Maller et al. 2008; Abraham et al. 2010; Rathmann 2020a, c). Contact with nature enhances positive emotions, which helps © The Author(s), under exclusive license to Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2023 J. Rathmann, Forest as a Health Resource, Springer essentials, https://doi.org/10.1007/978-3-658-42528-9_2

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to experience recovery from stress and mental fatigue (Ulrich 1983; Kaplan and Kaplan 1989; Ulrich et al. 1991; Hartig et al. 1996). Concentration is increased and incentives for physical activity are set (de Vries et al. 2010). Some studies suggest that the decrease in negative emotions is stronger during physical activity outdoors than during a comparable activity indoors, i.e., nature has an additional benefit, which can lead to an overall increased recovery (Thompson Coon et al. 2011). The restorative benefit of green spaces can be explained environmentally psychologically via the Attention Restoration Theory (ART) (Kaplan and Kaplan 1989) and the theory of stress reduction in natural environments (Ulrich 1983). While the ART tries to explain how the regeneration of attention capacity can succeed in natural environments, Ulrich (1983) assumes that, due to evolution, natural visual stimuli can be processed more easily by the brain than artificial ones. The human brain was always oriented towards natural stimuli during the time of human evolution, therefore artificial environmental stimuli are rather perceived as stressors; their processing is more strenuous and can therefore more easily lead to exhaustion effects. The health benefits of places can be framed in the concept of Therapeutic Landscapes1 and will now be specified for forests. The therapeutic aspect of a space is perhaps too narrowly defined in terms, as therapy generally presupposes the presence of a disease. It is demonstrated that forest visits can have a therapeutic effect, which impacts the general condition of people and can also generally support relaxation and stabilization of health. Therapy takes place in a doctor-patient relationship after diagnosis and can then pursue specific goals. This is clearly different from the so-called “forest therapy”, which can also be accompanied by a doctor or therapist in individual cases, but in a broader understanding, forest therapy is understood as the positive effect of forest visits on the physical, psychological, and social health of people. As a symptomatic therapy, a forest visit can aim to alleviate existing complaints without focusing on the triggering cause. The following will demonstrate which mechanisms lead to forest visits being able to increase the overall well-being of people. Therefore, forest therapy is understood here as a preventive therapy, a therapy that seeks to reduce the likelihood of diseases occurring.

1

On the concept of Therapeutic Landscapes: Rathmann (2020c).

2.1 Forests: Places of Spiritual Refuge and Encounter

2.1

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Forests: Places of Spiritual Refuge and Encounter

Forests are not only objectively describable, measurable, and assessable ecosystems for humans. People encounter forests as a whole person with affects, emotions, and also a metaphysical need for meaning. If one takes a comprehensive view of human health, these needs of people must also be satisfied in order for well-being and relaxation to occur. De Pater et al. (2021) show in their overview seven different dimensions of spirituality in their respective relationship to forests. The emotional dimension of personal experience refers to the aesthetic dimension, that of recreation, and that of connection with nature (see Sect. 2.2). Forests have always been attributed not only mystical aspects but also spiritual ones. Thus, forests—from the perspective of Christian creation doctrine—can be used ecologically sustainably and thus creation-preserving with a “creationoriented forest management”. This form of management has been operated by the Diocese of Passau for several years (Diocese of Passau 2023). This may be a marginal phenomenon in the overall forests of Germany, because; in Germany, the churches are losing a lot of their binding power whereas other forms of spirituality are gaining approval. Yoga, Zen meditation courses, Qigong, spiritual healing, channeling, energy work. Energy coaches, Reiki masters, fortune tellers, and others offer their services, which are used by many people. • Esotericism: in the original sense refers to a doctrine that is only accessible to a certain group of people. Esoteric help is often sought for psychological problems when people believe that evidence-based, scientific therapies and methods are ineffective or even harmful. • Spirituality: describes the devotion or immediate vision, the subjective experience of a transcendent reality, personal being affected. Spirituality remains essentially non-binding. • Religion: Belief in transcendent (heavenly, supernatural, extrasensory) powers, sacred objects, rituals, long historical traditions, seeks bindingness. In the secular, scientifically disenchanted worldview, there is actually no room for belief in angels, spirits, or magic. Yet esoteric thinking, from which many hope for healing, strengthening, serenity, or access to higher wisdom, remains widespread. Spirituality seems to gain approval to the extent that religions lose their binding power. In particular, Eastern spirituality with corresponding meditation approaches meets with great receptivity in the West. Spiritual values do not necessarily refer to a specific theistic religion; they rather describe the feeling of a connection with something else, which transcends one’s own self and has great significance for the individual dimension of meaning. This form of

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self-transcendence arises from the possibility of disregarding oneself and establishing a connection with other spiritual beings, nature, or fellow human beings. As a result, the self experiences an enlargement compared to the mere ego. This experience leads to the certainty of participating in the Other or Eternal. Rudolf Otto attempts to rationalize such seemingly irrational moments by schematizing the “irrational-numinous” (Otto 2014, p. 61) through rational terms in order to grasp the concept of the “holy”. For him, the central feeling of “creatureliness” is what he describes with the numinous (Otto 2014, p. 8 ff.). As a moment of the numinous, he presents the mysterium tremendum et fascinans, the feeling of the “awe-inspiring mystery” (Otto 2014, p. 13). A feeling that can culminate in awe and fear but also in ecstasy and rapture. The former describes the Old Testament fear of God (cf. Genesis 35:5), the latter the “Dionysian” (Otto 2014, p. 43). The dual character of the numinous described by Otto can also be applied to many areas of nature experience, which can evoke affective deterrence or enthusiasm. The basis of esoteric knowledge, on the other hand, is not divine revelation or the rational weighing of reasons, no supernatural power is deified; it is rather an ego-centric thinking that has created this modern spirituality with a large market through seminars, courses, and books. It is a form of permanent self-affirmation, which differs greatly from a lifelong critical self-examination, as is the basis of religious or ancient thinking. Transcendence, self-optimization, mindfulness, self-love are staged in a narcissistic attitude as a feel-good character of the ego. Numerous spiritual exercises are also performed in nature, in urban green spaces or in forests. Esoteric forest bathing offers also find approval. Spiritual experiences can be made in community but also individually in nature. Through forest contacts, combined with corresponding rituals, a spiritual experience can be lived in a special way, because forests, for example, often have a very long close spiritual significance2 . Already in ancient Greece and also in the Roman Empire, sacred groves, which serve for prayer and offering, are documented. Dodona’s description as an oracle site at a (sacred) oak grove in Homer’s Iliad can be described as a terminus post quem:

2

In numerous works on the health benefits of forest visits, however, this aspect is overlooked (Schuh and Immich 2019; Grilli and Sacchelli 2020; Rajoo et al. 2020). This may be due to the fact that a shortened biomedical health model is implicitly assumed.

2.1 Forests: Places of Spiritual Refuge and Encounter

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“noble zeus, god of the ancient pelasgians, god of the oracle and the oak in far-off, wintering dodona where you are surrounded by your priests,…” (Homer 2011, XVI, 233–235).

However, in the somewhat free translation by Raoul Schrott, the original term for ´ grove (αλσoς) has been lost. In the concept of Therapeutic Landscapes, Gesler (2003) describes the ancient cult site Epidaurus, which is dedicated to the healing god Asclepius, the son of Apollo, as a “healing space.” Even in Central and Northern Europe, dark groves, especially with oaks and their mistletoe branches, are documented as sacred sites by Celtic Druids. Roman sources describe “with a pleasant shudder and lustful disgust” (Kuckenburg 2004, p. 117) cruel human sacrifices at these sites, although it remains unclear whether these are first-hand descriptions or rather a specific death cult in the context of religious rites is being described. Much later, Christian monasteries took over the task of attributing religious significance to trees and forests. However, the initial task was to fell or clear specific trees that were considered the seat of pagan gods or places of revelation, in order to build Christian monasteries in their place. Thus, in the 8th century, Boniface, the missionary of Germania, had the oak dedicated to the god Donar felled at Geismar to demonstrate the power of the Christian God over the Germanic deity (Heid 2007). Forests became places of religious rites and worship, but also sources of income for the monasteries. Forests were places of penance, where a life pleasing to God could be led in seclusion and at a distance from the sinful world. Trees have great significance in Christian tradition; in the Old Testament they stand for the “Tree of Life” (Gen. 2:9, Revelation 2:7) and the “Tree of Knowledge” (Gen. 2:17). While the latter is primarily in the foreground in the description of Paradise, the “Tree of Life” is mentioned again in Revelation (2:7). In later tradition, the Tree of Life is given another meaning: The trunk is related to the wood from which Jesus’ cross was made. On this wood, Jesus dies to redeem the world of Adam, corrupted by the fall into sin, by reaching for the forbidden fruits from the Tree of Knowledge. The religious lyricist Jacopone da Todi (1230–1306) is credited with having embraced trees—suffused with holy light—as a symbol for the crucifix. He clearly describes this cross symbolism in a poem:

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2 The Health Benefits of Forest Visits “Caught on the cross, Love has hung” […]

O cross, to you I cling And I hold on strongly, That dying I may taste life; O death, you blessed, Adorned with life, Ah! That you are not given to me! Heart, want without trembling To strive after the wounds, That I may die in the pains of love.“ (da Todi 1864, LI, p. 302 f.).

In tree trunks, the crucifix is then recognizable and connects the Old Testament Tree of Life with that of Revelation. When old beeches are described as ”cathedrals of nature“, a Christian tree connotation continues to be evident. Much later, for example in the Weimar Classicism, the topos of the sacred grove is addressed again and again. Iphigenia serves as a priestess in the densely leafed, sacred grove, where she arrives, saved by the goddess Diana and abducted to distant Tauris: ”Out into your shadows, lively treetops Of the old, holy, densely leafed grove, As into the goddess’s quiet sanctuary, I still step with a shuddering feeling, As if I were entering it for the first time, And my spirit does not get used to it here.“ (Goethe 1925, p. 53).

Schiller has Ibykus enter Poseidon’s spruce grove with “pious shudder”, where he is then murdered (Schiller 2016, p. 759). Here it becomes clear that forests can also exhibit the frightening aspect that Tacitus had already described for the forests of Germania and, on the other hand, that forests reflect Otto’s mysterium tremendum et fascinans in a way.

2.1 Forests: Places of Spiritual Refuge and Encounter

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In Christianity, the fir tree, originally symbolized as the “Tree of Paradise”, represented the expulsion of Adam and Eve from Paradise. Nearly 30 million sold Christmas trees in Germany underline their economic significance as well.— Even today, in a supposedly secular society, forests carry spiritual attributions. In countries like Canada, for example, the spiritual values of the indigenous population must be taken into account in forest management. This also applies to urban forests, such as Stanley Park in Vancouver. These forests often encompass the traditional land of the First Nations (the indigenous population of Canada), so their interests receive special consideration (Konijnendijk 2008). Therefore, forest management must equally consider the recreational interests of a western society and the concerns of the indigenous population, which are expressed in spiritual meanings of forests and a great respect for nature (Lewis and Sheppard 2005). In environmental discourses, since the late 1980s, there has been an increasing reliance on the knowledge bases of indigenous cultures. This is associated with the belief that this traditional ecological knowledge (TEK) can significantly contribute to implementing sustainable environmental protection as a complement to western science, technology, and corresponding environmental practices (Berkes 2012). Various studies of such ethnosciences also address the question of where old sacred groves can serve the interests of species protection. However, Oyeleke et al. (2017) show, using the example of the UNESCO World Heritage Site of the Sacred Grove of the Goddess Osun in Nigeria, that inadequate information flows and poorly organized management structures effectively hinder development potential.—In the West African Republic of Benin, there are about 2940 sacred forests, covering an area of 18,360 hectares (0.16% of the country’s area). These forests have great socio-cultural but also increasingly ecological significance. However, a rapidly growing population has caused the forest areas to decline (Imorou et al. 2017). Traditional rites, for which the forests are visited; for example, because ancestors are buried there or sacred shrines have been erected, can then indirectly be used as a vehicle to protect the forests and their biodiversity. However, such practices are also threatened by the spread of other religions, similar to how pagan trees were felled in the name of Christianity. However, even in secular western societies, a close connection between forest and spirituality remains. Wayside crosses, forest cemeteries, and burial forests are examples of this. Another aspect lies in the ecological advantages of urban forests for a space: Quinton et al. (2020) show, using the example of Halifax, Nova Scotia (Canada), how tree plantings in urban cemeteries could lead to new urban forests and there is room to double the number of trees there. This would

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be the opposite process, not bringing the graves into the forest, but rather planting the forest around the graves. Another bridge from the (in the forest) lived spirituality to the health of an individual lies in the dimension of meaning. Because in a salutogenic perspective, meaning is a very decisive resistance resource in maintaining and strengthening health (cf. Rathmann 2020a, p. 173 ff.). Meaning can be found through family or work, but especially in times of severe stress and illness, spirituality and religiosity prove to be central resources of meaning (Bucher 2011, p. 127 f.). Because finding meaning with an eternal perspective can have a great relaxing effect. Furthermore, a spiritually/religiously lived life often positively affects physical health through a more moderate lifestyle and the psychological side of health as well through relaxation and community experience (cf. Bucher 2011, p. 100 ff.). This is especially true for modern forms of spirituality from the wellness sector, where in contrast to traditional religious experiences, happiness is sought exclusively in the earthly here and now.

2.2

Human-Place Relationships

People construct their environment in a certain way based on their socialization and cognitive abilities through symbolic attributions and through emotional and affective reactions to a specific environment. Such personal attachments to the space that surrounds a person are addressed in manifold concepts of humanplace relationships. Places are created through an affective and emotional bond and through the attribution of meaning and/or significance to a specific individual place, often described with the English term “place”. Home and homesickness are likewise place attributions with individual meaning content (Berr 2019). Through this individual appropriation of space through attributions of meaning, specific places are qualitatively constructed, which can no longer be reduced to scientifically describable and quantifiable spaces. This subjective attachment to a place can be described as a “sense of place”, which is embedded in a place where a person is located and which can be concretely located as part of the geographical coordinate system. A place, therefore, that can also be characterized by a specific material equipment; be it a forest area or a city landscape, supplemented by the subjective, affective and emotional bond to this place. If forests are considered places of longing, it is not surprising that individual bonds and thus attributions of meaning are immortalized by carving signs, names or initials into tree barks (see Fig. 2.1). Thus, places receive an emotional charge that is not found in a mere description of the physical environment. The concept of “place attachment”

2.2 Human-Place Relationships

17

is composed—following the triadic model of Scannell and Gifford (2010)—as follows: • Place (physical, social place; in Fig. 2.1 it is the tree trunk) • Process (affect, cognition, behavior; in Fig. 2.1 it is love, which is expressed in the action of carving into the tree trunk) • Person (individual or group; in Fig. 2.1 it is apparently an individual) “Place attachment” describes a person’s bonds to a specific place through behavior, affects, and cognition (Scannell and Gifford 2010, 2016). Such positive (but also negative are possible) place attributions as interaction with the physical environment can have a balancing effect on a person, because it strengthens selfconfidence by building a psychological balance between extreme emotional states (Korpela 1989).

Fig. 2.1 Individual human-place bonds often reveal an emotional attribution of meaning on trees. (City Forest Augsburg 2023, Photo: © Rathmann)

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In forest management strategies, personal attachments to a place are increasingly taken into account in recreational forests (Wynveen et al. 2018). Numerous other concepts attempt to empirically test and theoretically substantiate humanplace bonds (in a broader sense: biophilia, biophobia, place identity, place dependence, topophilia, solastalgia, nostalgia, cf. Albrecht 2005), i.e., affective bonds that people build with the surrounding nature, environment, or landscape. However, these concepts are accentuated differently in terms of methodology and content depending on the author, which makes a clear-cut definition difficult. The specific place, however, always remains the space where a person experiences and interacts with the environment in a different temporal dimension. Therefore, the state of being sick or healthy always has a spatial dimension, which influences complex personal experiences.

2.3

Forest Climate

Depending on their constitution or pre-existing conditions, people react differently to atmospheric environmental variables. Their effects on the human organism can be divided into four human-biometeorological complexes of effects (cf. Trenkle 1992, p. 19 ff.): • The thermal effect complex Heat and cold stimuli can put a strain on the human organism. The thermoregulation of a person is influenced by subjective perception but also by physical activity, clothing, and the deliberate seeking out of sunny or shady places. • The photoactinic effect complex refers to the effects of solar radiation on humans; this includes not only the wavelengths of visible light but also longwave infrared radiation and short-wave UV radiation. • The chemical effect complex refers to the respective air hygiene situation and includes all liquid, solid and gaseous air admixtures that have an influence on the human organism; these can be pollen as well as fine dust from anthropogenic sources or ground-level ozone. High concentrations of pollutants in the air can lead to various health burdens and can also lead to increased mortality. • The neutrope effect complex includes all weather and climate-related influences that affect people’s well-being. A special stimulating climate at health resorts can have positive effects; rapid weather changes or a foehn event can

2.3 Forest Climate

19

lead to significant disturbances in well-being among sensitive or vulnerable population groups. The forest climate can be vertically divided into the canopy, the trunk space, and the ground space. For the forest visitor, the trunk space is generally climatically relevant. Depending on the vegetation, tree species, stand height and density, the climate inside a forest differs from the outer area of the forest and the open land. However, a specific local climate is always pronounced, which offers the visitor many human bioclimatic advantages compared to the open land. It becomes clear that forests have a pronounced mild climate3 : The daily course of temperature and humidity is balanced, the direct solar radiation is reduced, the air movements are also reduced. The reduced wind speed also means that sound can spread less; in addition, sound waves are reflected by the leaves and lose energy in the process, which also leads to forests generally being quieter than open landscapes. The positive human bioclimatic effects of forest climates primarily lie in air quality and cooling effects. These can be attributed to increased evapotranspiration and shading effects (e.g., Bowler et al. 2010; Livesley et al. 2017). Beck et al. (2018) demonstrate, using the example of the city of Augsburg, daily and seasonal weather-dependent average temperature differences between urban forest and settlement areas of up to 5 °C. These cooling effects compared to the heavily sealed urban space can become effective in their surroundings. Especially during hot summer days, urban forests can effectively contribute to mitigating the heat stress of city dwellers. In addition, lower air temperatures can increase physical performance. Forest paths increase the motivation to engage in sports activities, and the soft forest floor and the forest climate alike invite joint-friendly running. Even in rainy cool weather, a stay in the forest can enhance personal well-being, as the climatic stimuli there only unfold dampened. The same applies to direct sunlight, which hardly penetrates the forest floor depending on the density of the forest, as it is reflected and absorbed by the crowns. In winter, the heat radiation occurs at the crowns, reducing the radiation near the ground; on cold winter days, coniferous forests can therefore be somewhat warmer than the surroundings. In addition, forests can absorb air pollutants more effectively than other forms of vegetation due to their large crown surface area. The surface roughness of forests ensures that aerosols in particular can be well filtered from the air. A filtering effect of approximately 60 tons of dust per hectare of forest area is 3

General stress factors (e.g., heat stress), protective factors (clean air conditions), and stimulating factors (e.g., intense solar radiation, gusty wind) can also be distinguished with regard to the effects of weather and climate on the human organism.

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achieved annually (Moll 2013; cited in: Schuh and Immich 2019, p. 34). The resulting reduced proportion of air pollutants relieves the respiratory tract, but also the skin; the increased humidity also has a positive effect on the respiratory tract of forest visitors. The increased humidity is due to the evaporation area on the forest floor and the reduced wind speed. However, a resulting increased heat content of the forest air can also be perceived as oppressive humidity, especially on hot days. On cold days, however, the reduced wind speed offers protection from cooling, especially in coniferous forests. Urban forests in particular have an important role in climate adaptation to counter an increase in potentially health-relevant climatic stress situations— such as heatwaves. This is especially the case because the urban population is continuing to grow globally and an aging population and therefore increasing vulnerability to health stresses is to be expected in Western societies.

3

Shinrin Yoku: Forest Bathing

Forest bathing describes immersing oneself in forests to slowly and consciously absorb all impressions there, to gather new strength, and to experience relaxation and recovery from everyday life. This corresponds to a forest therapeutic approach, which serves both disease prevention and the maintenance of physical and mental health. Is this just a fashion trend? A marketing gimmick? Old wine in new bottles? Or something completely new? Well, the forest bathing offer is now very diverse, so there is no simple answer to this and with the variety of offers, it is certainly a bit of everything. The Japanese term “Shinrin-Yoku” describes such slow forest walks; a term that is now also experiencing strong popularization in the West. In this conscious reflection on oneself and the surrounding impulses and stimuli, individual wellbeing can be increased (see Tsunetsugu et al. 2010). Especially in Japan, this form of preventive medicine was also heavily promoted to encourage more people to strengthen their health through forest visits. There are now over 60 forest therapy trails there (Miyazaki 2018, p. 12). The ultimate goal is also an economic one; if people can reduce stress in nature, this can have a preventive effect against numerous stress-induced civilization diseases. Chronic stress can intensify flulike effects, as well as back pain, obesity, sleep disorders, depressive moods, stomach complaints, heart diseases, or even increase the risk of cancer (Miyazaki 2018, p. 33). This is ultimately due to the fact that our body, through its long evolutionary history, is adapted to a life with and in nature. The urban lifestyle contradicts our nature. Positive health effects from forest visits can thus relieve state health expenditures and especially in countries where the population is aging significantly and © The Author(s), under exclusive license to Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2023 J. Rathmann, Forest as a Health Resource, Springer essentials, https://doi.org/10.1007/978-3-658-42528-9_3

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lives largely in cities, this is an important political argument for protecting forests as an ecosystem and recreational area.

3.1

Multisensory Forest Experience

General well-being increases during forest visits, while negative emotions and stress perception are reduced. The activity of the autonomic nervous system, the sympathetic and parasympathetic, can be measured in humans through heart rate variability. During relaxation, the activity of the parasympathetic nervous system increases, while under stress the sympathetic shows increased activity. The relaxation effects in the forest can be measured by a slowing of heart and breathing rate and a slight decrease in blood pressure (Park et al. 2010; Ideno et al. 2017). The positive health effects therefore go beyond short-term well-being, because the reduction in blood pressure can overall reduce the risk of heart and vascular diseases. Shirin-Yoku is designed as a multisensory forest experience in Japanese and South Korean tradition (Hansen et al. 2017). In slow walks, interrupted by breaks, different senses are addressed (cf. Schuh and Immich 2019, p. 14 f.; Rathmann 2020c): • The subdued light in the forest and the constantly changing play of light and shadow make visual impressions constantly vary and support a form of undirected attention, which contributes to relaxation (Kaplan and Kaplan 1989). In visual experience, there are—just as there are negative, even dangerous experiences in the sense of taste—forest structures that can cause displeasure. Deadwood, standing or lying dead trees, branches or twigs can evoke ambivalent reactions in forest visitors (Rathmann et al. 2020b). • Natural smells are particularly noticeable in conifers after rain events or during dryness through volatile terpenes in the olfactory perception (Cho et al. 2017). In addition, it can be shown that the smell of dried wood reduces prefrontal brain activity, which contributes to physical relaxation (Miyazaki 2018, p. 172 f.). • Compared to an urban environment, forests are quieter, so that natural sounds, such as the babbling of a brook, the rustling of leaves or bird calls, are clearly and variedly presented. These factors noticeably contribute to the improvement of individual mood (Benfield et al. 2014).

3.2 Mindfulness

23

• Different rough tree barks, mosses or leaves can stimulate tactile sensors. Koga et al. (2013) show how touching plants, as opposed to other objects, has a calming effect. • The sense of taste can be addressed by tasting forest berries, wild plants or mushrooms.

3.2

Mindfulness

Some forest bathing programs are supplemented or based on various mindfulness exercises. The aim is to enhance the perception of one’s own body and/or the environment. Attention is specifically directed to consciously allow a close connection of body, mind, and emotion. One goal is to strengthen self-efficacy, and sometimes also self-optimization, satisfaction, and resilience. At the same time, emotional self-regulation can be achieved by distancing oneself from negative emotions and burdensome thoughts. Such exercises are entirely in the here and now and are intended to perceive the present clearly but without judgment. The full presence of a person is required to fully grasp a moment. Mindfulness exercises in a forest environment can now benefit from the additional health benefits that forests offer. Especially mindfulness-based stress reduction (MBSR) can be successfully implemented in a natural environment. Because, when these exercises are performed there, the perception of stress and depressive moods decrease more than in an urban environment or indoors (Choe and Sheffield 2022). The background of MBSR lies in Far Eastern Buddhist meditation techniques and is based on practicing an attitude that can have a stress-reducing effect. The American physician Jon Kabat-Zinn developed mindfulness programs in the late 1970s, the effectiveness of which has since been proven by numerous studies (Khoury et al. 2015), although it remains methodologically challenging to clearly quantify these effects compared to control groups, as they are very personal and thus individual experiences (Lam et al. 2022). However, mindfulness exercises can also have negative effects when unconscious and repressed issues become apparent (Britton et al. 2021). Mindfulness exercises often have their origins in Far Eastern thinking. The fact that these Buddhist traditions of thought meet with such a high level of receptivity in the West is surprising, as Western individualism, heightened as narcissism, is initially completely contrary to a Buddhist religion in which the individual is not granted any actual being. Buddhism is a religion without God and without a free

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Shinrin Yoku: Forest Bathing

individual, an individual therefore has no essence of its own. Being human is based on karma, thus on the gains or losses of previous existence; only a positive way of life can then lead to enlightenment. Mindfulness exercises are ultimately intended to help dissolve a person’s painful attachment to the self, in order to escape Samsara, the continuous cycle of life (death, birth, becoming, passing away) and to reach Nirvana and merge into an Absolute. Christian approaches to mindfulness exercises also aim to get rid of inner tensions, but at the same time want to enable an opening for a higher meaning in life (Symington and Symington 2012). The conscious inclusion of nature, of creation, could intensify and deepen such exercises.

3.3

Effects on the Human Body

Further positive health aspects of forest visits can be described, which directly and indirectly affect human physiology. The effects of volatile organic carbon compounds on the immune system are discussed in popular scientific presentations as a positive effect of forest visits. This refers to various substances that plants produce and emit as protection against pathogen infestation. These BVOCs (biogenic volatile organic components) exhibit high chemical reactivity and are collectively referred to as phytoncides, often appearing as terpenes in molecular structure (Zemankova and Brechler 2010). These are often described as active substances in the activity increase of natural killer cells. Li et al. (2008a) show positive effects in this regard; in 13 nurses, aged between 25 and 43 years, an increase in the activity of natural killer cells can be demonstrated after a threeday forest stay, along with a simultaneous reduction of stress hormones. Li et al. (2008b) and Kim et al. (2015) can confirm comparable effects, but the study by Mao et al. (2012) cannot. Overall, there is still no reliable evidence about the activation of killer cells during a forest stay and a positive effect linked to cancer diseases. This is because the estimation of effect sizes of very volatile substances with very different concentrations on individual forest visitors is enormous, and the cause-effect mechanisms derived from this are still unclear in detail, also lacking studies with large numbers of participants and corresponding comparison groups. However, other physical effects are more clearly proven. The cortisol level can be used to assess the stress level of individuals. Cortisol is released more intensively under stress by the adrenal glands and is therefore a suitable indicator of the activity of the sympathetic nervous system. Forest stays lead to a reduction in cortisol levels, which are then linked to further effects such as reduced tension

3.3 Effects on the Human Body

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and fewer negative emotions (Hansen et al. 2017; Kobayashi et al. 2017). Even a short forest walk of 20 minutes can significantly reduce stress hormones and thus contribute to relaxation, regeneration, and recovery (Hunter et al. 2019). Cardiovascular parameters (e.g., blood pressure, pulse, or heart rate variability) can also be used as health indicators during forest visits and show corresponding positive effects of forest environments on humans (see Park et al. 2010; Rathmann et al. 2020a). Another positive health effect could arise from the higher number of microbes in forests, compared to an urban environment. The entirety of a human’s microorganisms is referred to as the microbiome or microbiota. These are found on the skin, mucous membranes, and in the organs. For several years, particular attention has been paid to the microbiome of the human gut in research. Protective bacteria are found here; however, disturbances can lead to health problems. A high diversity of protective species is important for strengthening and maintaining health; less so the absolute number of organisms. By now, not only functional gastrointestinal disorders (e.g., irritable bowel syndrome) are associated with impoverished microbiota, but other diseases could also be traced back to it (Blum 2017). Arrieta et al. (2015) were able to show that the reduction of certain bacteria in the first 100 days of life in children increases the risk of asthma and other atopic diseases (eczema, hay fever, and other allergies) are apparently related to the diversity of the microbiome (Bisgaard et al. 2011). The composition of the microbiome depends not only on diet but also on the host’s environment. Because soils, but also the human gut, contain a high number of active microorganisms. However, the diversity of the microbiome in the human gut is only about 10% of the biodiversity of the soil and decreases drastically with the modern lifestyle (Blum et al. 2019). Forests have an extensive microbiome presence, which is found in the soils, but also in the forest air. These occurrences could have a positive effect on humans through skin and respiratory contact (Schuh and Immich 2019, p. 83). Exposure to a diverse microbial environment is important for the development of stable immune tolerance, not only in early childhood (Roukolainen 2017). The extensive natural microbiome of the forest could interact with the skin and the respiratory tract, thus positively influencing human immune regulation. As early as 2001, Riedler showed in a much-cited study that contact of small children with stables on a farm and the drinking of non-pasteurized milk is apparently associated with a reduced occurrence of asthma and hay fever. Ruokolainen et al. (2015) were able to show in their study with 1004 participants aged 0.5 to 20 years that the immediate living environment within 2–5 km distance to forests and agricultural land leads to a reduced occurrence of atopy. 20% of the variation in the relative frequency of Proteobacteria on the skin of healthy study

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participants can be explained by land use (forest, agricultural area). Therefore, exposure, especially in early years of life, to a green environment seems to positively influence the human immune system through the environmental microbiota. A finding also confirmed by Roslund et al. (2020). They examined the ratio of microbiomes in forest soils and the immune values of 36 children at four daycare centers in Finland. Within 28 days, the amount of anti-inflammatory and proinflammatory messengers and regulatory immune cells in the blood, as well as the diversity of the children’s skin and gut bacteria, were analyzed with control groups. For this purpose, natural forest soil with moss and shrubs was brought to previously unplanted outdoor areas of the daycare centers. The children spent about 1.5 hours on these areas; the diversity of three out of four examined bacterial classes increased compared to children in a control group. It had approached the values of children from nature-oriented daycare centers, which served as a second comparison group in the study. So far, the health benefits of microbes in the air and soil are not yet firmly anchored in the awareness of decision-makers, at the same time there are still considerable gaps in knowledge in quantifying the regulatory performance of microbes on the human organism.

4

Forests in Climate Change

Natural forests have adapted their species composition, including all animals, plants, fungi, and microorganisms, to specific climates. Climate envelopes describe the range in which a particular tree species can thrive well under the given annual precipitation totals and average annual temperatures. If the climatic conditions, such as precipitation and temperature at the respective altitude but also distribution, change, ecosystems must adapt accordingly. However, the changes in the context of the anthropogenically enhanced greenhouse effect are too rapid for many ecosystems, so that adaptation is not possible and permanent damage to the ecosystems occurs. Trees require long periods of time to colonize new areas. Reconstructions of the recolonization of open landscapes by trees after the last ice age show that 50 to 1000 years are needed to recolonize a 50 km wide area (Winnett 1998). However, the anthropogenically enhanced greenhouse effect requires migration rates of trees that, although varying from species to species, are much faster. Therefore, how future forest ecosystems develop depends on the regional change in climate but also on the respective forest management, as only the smallest part of the forests in protected areas will be left to themselves. But there are also other aspects: Plants need CO2 for their growth, therefore an increase in atmospheric CO2 content promotes growth in many trees in the middle and higher geographical latitudes. This is accompanied by an extended growth period for the plants due to higher temperatures. However, opposite effects can also be observed: increasing drought at higher temperatures can reduce tree growth. An increase in climatic extreme events also puts a lot of strain on forest areas. Droughts can induce forest fires, storm events can uproot trees, damaged trees can easily be infested by insects. An additional increase in temperature means that © The Author(s), under exclusive license to Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2023 J. Rathmann, Forest as a Health Resource, Springer essentials, https://doi.org/10.1007/978-3-658-42528-9_4

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Forests in Climate Change

pathogens and insects can also settle in, which were previously native to other regions of the earth and to which the trees are not yet adapted. This threatens the stability and vitality of many forest stands and the ability of forests to provide certain ecosystem services can be restricted. Therefore, silvicultural management concepts must adapt to the changed and further changing climatic conditions. However, the great challenge is that very long periods of time have to be bridged. Forest conversion measures on a timescale of several decades face the challenge that the climatic but also societal conditions can hardly be predicted precisely. At the same time, it is necessary to identify the areas that are exposed to greater risks than others. Forests will continue to be valuable and protectable systems in the future due to their numerous ecosystem services. To what extent future forests will change in their recreational performance is currently not foreseeable; but however the forest structures change: forests remain ecosystems where people can find peace, relaxation and recreation.

5

Outlook

The human-nature relationship has long shown strong tendencies of division (cf. Rathmann 2020b), which also manifest in an increasing destruction of global ecosystems. This ultimately inflicts great harm on humans and their health. Because global pandemics are also an expression of the fact that humans are increasingly interfering in previously barely touched ecosystems, thereby enabling new transmission paths for zoonoses. Forests provide numerous ecosystem services, with the climate protection function and the recreational service currently being strongly discussed. For an increasingly urban global population, visits to the forest offer an opportunity to experience nature as well as relaxation and recreation. However, despite the current strong popularization of forests as wellness oases, there are also real dangers to human health during forest visits: bears, wolves, falling branches, ticks, or allergens. Clearcuts, garbage in urban forest areas, and sometimes large crowds there are further aspects that can negatively affect the forest experience. Nevertheless, there is now strong empirical evidence for positive health effects of forest visits. These relate to physical, mental, and social aspects. Forest visits stimulate movement, reduce stress, help restore concentration and attention, enable relaxing nature observation as well as the maintenance of social contacts. Overall, forests are multisensory recreation spaces, which can gain additional importance for the individual through affective bonds, personal attributions, and symbolic charging. Many of the positive effects that forest visits can have on human health can also be partially experienced in green spaces, parks, or other landscapes; however, in sum, supplemented by the health benefits of the forest climate, it becomes apparent that forests (initially in the middle geographical latitudes) © The Author(s), under exclusive license to Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2023 J. Rathmann, Forest as a Health Resource, Springer essentials, https://doi.org/10.1007/978-3-658-42528-9_5

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Outlook

represent excellent recreation spaces with the potential to maintain, strengthen human health and accelerate convalescence. Therefore, the protection (not only) of forests ultimately also corresponds to the protection of an important health resource for humans.

What you can learn from this essential

• Forests fulfil numerous functions and ecosystem services. • Forests store greenhouse gases and are therefore regarded as “climate protectors”. • Forests create their own forest climate, which is characterised by reduced air temperatures, increased humidity and a lower air-hygienic load. • The salutogenetic perspective on disease and health emphasises resources that help maintain health—forests can provide such resour • Forest visits are multi-sensory experiences that have the potential to strengthen people’s physical and mental health. • Places acquire a specific meaning for the individual through symbolic attributions, which complement the objectively describable space and lead to individual relationships to place. • Numerous positive effects of forest bathing on human health can be scientifically proven. Mindfulness exercises can enhance such effects.

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2023 J. Rathmann, Forest as a Health Resource, Springer essentials, https://doi.org/10.1007/978-3-658-42528-9

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