Ecological restoration is a rapidly growing discipline that encompasses a wide range of activities and brings together practitioners and theoreticians from a variety of backgrounds and perspectives, ranging from volunteer backyard restorationists to highly trained academic scientists and professional consultants. This book offers a comprehensive and coherent account of the field for everyone who initiates, finances, designs, administers, issues government permits for, manages, and implements ecological restoration projects, and all those who serve in supportive roles. Originally published in 2007, this revised and reorganized edition brings the book up to date with new developments and current trends in the field.
In a lively, personal fashion, the authors discuss scientific and practical aspects of the field as well as the human needs and values that motivate practitioners. The book identifies fundamental concepts upon which restoration is basedconsiders the principles of restoration practiceexplores the diverse values that are fulfilled with the restoration of ecosystemsreviews the structure of restoration practice, including the various contexts for restoration work, the professional development of its practitioners, and the relationships of restoration with allied fields and activities
The book also includes case studies and Virtual Field Trips around the world that illustrate points made in the book with on-the-ground information from those who were intimately involved with the projects described. Throughout, ecological restoration is conceived as a holistic endeavor, one that addresses issues of ecological degradation, biodiversity loss, personal engagement, and sustainability science simultaneously, and draws upon cultural resources and local skills and knowledge in restoration work.
|Series:||Science and Practice of Ecological Restoration Series|
|Edition description:||Second Edition|
|Product dimensions:||7.10(w) x 10.10(h) x 0.90(d)|
About the Author
Andre Clewell taught botany at Florida State University in Tallahassee for 16 years. He has also served as president of the Society for Ecological Restoration. He is currently a privately consulting restoration practitioner and plant ecologist. James Aronson is a restoration ecologist at the Center of Functional and Evolutionary Ecology, Montpellier, France, and at the Missouri Botanical Garden, in Saint Louis, Missouri. He is also Editor of the book series Science and Practice of Ecological Restoration, published jointly by the Society for Ecological Restoration and Island Press.
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Principles, Values, and Structure of an Emerging Profession
By Andre F. Clewell, James Aronson
ISLAND PRESSCopyright © 2013 Andre F. Clewell and James Aronson
All rights reserved.
Ecological restoration is the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed (SER 2004). From an ecological perspective, it is an intentional activity that reinitiates ecological processes that were interrupted when an ecosystem was impaired. From a conservation perspective, it recovers biodiversity in the face of an unprecedented, human-mediated extinction crisis. From a socioeconomic perspective, ecological restoration recovers ecosystem services from which people benefit. From a cultural perspective, ecological restoration is a way that we strengthen our communities, institutions, and interpersonal relationships by participation in a common pursuit. From a personal perspective, ecological restoration allows us to reconnect with the rest of Nature and restore ourselves as we restore impaired ecosystems. All of these perspectives on ecological restoration distill down to a simple truth: Nature sustains us; therefore, we serve our own interests when we reciprocate and sustain Nature.
While globally cumulative, ecological restoration is necessarily a local endeavor. The decision to restore represents a long-term commitment of land and resources. Ideally, that decision is reached in consensus by all who are affected. A restored ecosystem contributes to peoples' ecological and socioeconomic security and their well-being into the indefinite future. The benefits of ecological restoration are intergenerational. People develop appreciation for local ecosystems when they participate in decisions regarding restoration, and their respect for ecosystems increases if they become actively engaged in restoration activities.
Ecological restoration reinitiates ecological processes, but we cannot intervene and create desired outcomes directly. Instead, we manipulate biophysical properties of an impaired ecosystem to facilitate resumption of processes that can only be performed by living organisms. The restoration practitioner assists ecosystem recovery much as a physician assists the recovery of a patient. Patients heal themselves under the physician's supervision, care, and encouragement. Similarly, ecosystems respond to assistance provided by restoration practitioners.
Once ecological restoration project activities are completed, a successfully restored ecosystem self-organizes and becomes increasingly self-sustaining in a dynamic sense. It again becomes resilient to disturbance and can maintain itself to the same degree as would be expected of an undisturbed ecosystem of the same kind in a similar position in the local landscape. In other words, the intent is to recover an impaired ecosystem to a condition of wholeness or intactness. A "whole" ecosystem is characterized by possession of a suite of ecological attributes that are discussed in chapter 5. We use the term holistic ecological restoration to distinguish such comprehensive efforts from partial restorative actions that are limited to incremental ecosystem recovery or ecological improvement.
In spite of our ideal to recover an impaired ecosystem to a condition of total self-sustainability, the era of Earth's history when intact ecosystems were entirely self-sustainable has come to a close, for two reasons. First, human-mediated environmental impacts have become so pervasive globally, and often so severe locally, that many restored ecosystems require ongoing ecosystem management to prevent them from slipping into an impaired state once again. Second, many seemingly natural ecosystems coevolved with human inhabitants, whose traditional cultural practices have transformed them into semicultural ecosystems. Such systems degrade from disuse following abandonment and become candidates for ecological restoration. If they are restored to their semicultural state, then cultural practices that previously maintained them should be resumed to ensure their sustainability.
Ecosystems are not static. They evolve in response to natural and anthropogenic modifications in the external environment and to internal processes that govern species composition and abundance. We use evolve and evolution with respect to ecosystems here and elsewhere in this book, not in a Darwinian sense, but in a developmental sense to indicate unidirectional or cyclic ecological change through time. Ecosystem evolution, just like the evolution of species, is sometimes gradual and subtle and at other times rapid or abrupt. A record of the sequential changes in expression that an ecosystem undergoes through time is called its historic ecological trajectory. If an ecosystem is impaired, its historic trajectory is interrupted. Ecological restoration allows an ecosystem to resume its historic trajectory. This is similar to a physician assisting in the healing process, so that patients can resume their lives.
During the hiatus caused by impairment, the Earth has not stood still. External conditions and boundaries may have changed, and the internal processes of ecosystem recovery may cause ecosystem expression that was not formerly present. Therefore the outcome of ecological restoration is necessarily a contemporary expression and not a return to the past, even though many if not most species may well persist from past to future on most sites. In this way, ecological restoration connects an impaired ecosystem to its future. We restore historical ecological continuity, not historic ecosystems. Regardless of how much we try to restore to the past, it never happens. We have no choice in this matter, because we can't control outcomes of restoration without losing the quality of naturalness that we ultimately strive to recover. At best, we can only emulate the past as we restore. The reason for this is that ecosystems consist of living organisms, and life does not run backward. In many restoration projects, the future state emulates the gross structural aspects of the preimpairment ecosystem, but to believe it can ever truly return to that former state—as if time were reversible—is wishful thinking and counterproductive. We invariably restore ecosystems "to the future." Consequently, ecological restoration is in some ways a metaphor that should not be taken literally. Nonetheless, it is a powerful metaphor, and a path to follow in troubled times, which has captured the imagination, hearts, and minds of people globally.
All ecological restoration projects are case specific, and it is much easier to restore some impaired ecosystems than others to something that approaches a prior historic state. However, the intent in every case should be to nudge the system back onto its ecological trajectory that—prior to impairment—was in the process of developing toward a sometimes indefinite future. Attempts to restore an ecosystem to its former, historic state are valid and viable as long as it is understood that the outcome will be imperfect, and that in every project our overarching goals are to restore historic continuity and ecological wholeness rather than stasis.
We live in a time of increasingly environmental instability. Human-mediated exploitation and abuse of the natural environment, and ongoing changes in climate and other global conditions, dictate that many ecosystems can only be restored to states that contain species substitutions and rearrangements of structure with which we are unfamiliar. Restoring to previously unknown states may seem paradoxical, but this concept is no different from the open-ended nature of ecosystem evolution throughout geological time. What makes ecological restoration distinctive is that we rely insofar as possible on past expressions of the preimpairment ecosystem as our reference or starting point and salvage whatever legacies from the past that we can in order to ensure a fully functional, dynamic, and sustainable ecosystem in the future. In particular, we populate the restored ecosystem with species from the predisturbance ecosystem to the extent that contemporary conditions allow. These species coevolved or are otherwise adapted to function seamlessly with one another and the physical environment. They are more likely than other species to assemble themselves into satisfactorily restored and sustainable ecosystems. They provide historic continuity and return an ecosystem to its historic ecological trajectory.
The pace of recent environmental change, coupled with the magnitude of contemporary losses of biodiversity, has quickened ecosystem evolution, generally leading to their impoverishment through simplification and consequent destabilization. Impoverishment is the price we pay for uninformed actions or callous disregard by previous generations and by those of us who indiscriminately transform landscapes, pollute ecosystems, and deplete resources. The vision of restoration, however, gives hope that through our efforts, we can recover ecosystem complexity and once again enjoy the personal, cultural, and economic benefits of functional ecosystems and the biotic grandeur they contain. It suggests that we can undo at least some of the ecological and environmental damage people have caused in the past, and that—despite our ongoing demographic explosion—we can clear new paths for sustainable economic development. The restored ecosystem shown in figure 1.1 demonstrates that ecological restoration is indeed possible and has been accomplished. Such paths must be based on the recognition that our economies depend entirely, in the first and last analysis, on natural capital—the wealth produced by fully functional ecosystems and their biodiversity. Unless we restore this capital, and learn to live on the interest rather than recklessly spending down our reserves, we are doomed to impoverishment at many levels, and possibly to unprecedented economic and ecological catastrophes. The enriching paths of restoration lead to sustainability and reintegration of people with the rest of Nature.
Some Basic Terms and Concepts
Before going further with our main topic, we pause now to offer explanations of several terms and concepts that recur throughout this book, especially for the benefit of those who are not particularly familiar with ecology. The meanings of some of these concepts lack consensus among professionals, and the following discussion explains how we will employ each of these key terms in this book. We have defined additional terms in the glossary that appears at the end of the book, and all terms appearing in the glossary are printed in italics the first time they appear in the text. By and large, we follow usage employed in the first edition of this book (Clewell and Aronson 2007) and in the second edition of van Andel and Aronson's graduate level textbook (2012). A few nuances or changes do, however, occur here, which is only normal given the high speed at which this field is evolving today. We also acknowledge cases where ambiguity remains, and we refer to other published sources for further reading and comparison in these instances.
A state is the manifestation or expression of an ecosystem, particularly its biotic community. Abiotic—nonliving—aspects of an ecosystem, such as its geology, topography, and so forth, contribute to the state as the setting or backdrop for the biotic community. A system's biotic community is governed by its species composition and community structure. The latter is a function of the sizes, life forms, abundance, and spatial configurations of its species. When we use the word state in this book, we refer to an ecological state.
Process and Function
Organisms and species populations in an ecosystem don't just sit there, as if they were museum specimens. They grow, assimilate, respire, compete for resources, and reproduce. If they are plants, they photosynthesize, absorb water and nutrients, and transpire. If they are animals, they move about in search for water and food; they fight or take flight, they compete for mates or advertise for the same. If they are microorganisms, they decompose dead organic matter, release nutrients, fix nitrogen, and transform nitrogenous compounds. All of these activities are biological processes. During the course of any given process, energy is transformed, expended, or stored. Matter is combined, separated into its components, or moved from one place to another. Some of the more important ecological processes include primary production; demographic regulation of species populations by means of herbivory, predation, and parasitism; energy transfers in trophic linkages, nutrient recycling; storage of carbon in humus; soil formation; microclimatic regulation; moisture retention; and many symbiotic interactions, such as animal-mediated pollination and seed dispersal, mycorrhizal exchanges of nutrients and energy, and nitrogen fixation by microorganisms living in symbiotic relationships with more complex organisms. These are processes that we associate with ecosystems. We associate other ecological processes with the biosphere level of organization, such as the generation of atmospheric oxygen during photosynthesis, which of course can be studied at the level of ecosystems. Another ecological process of significance to the biosphere is thermal regulation of the Earth's atmosphere, mainly from transpiration, which reradiates heat into space. When a biological system at any level of organization (cell, organism, community, biosphere) participates in a biological process, we say that it is functioning or functional, which indicates that biological work is being performed in the sense that physicists use the term.
In recent years, some ecologists and environmental economists, lawyers, and other professionals concerned with natural resources have used the terms function and ecosystem function in a distinctly different manner from ours to designate collectively those natural ecosystem services that benefit people and their socio-economic well-being. Examples of ecosystem services are retention of potential flood waters, improvement of water quality, erosion control, provision of range for grazing by domestic livestock, provision of habitat for desirable wildlife, and venues for recreation. To avoid confusion, we use the term ecosystem services to designate socioeconomic benefits that people derive from ecosystems, and we avoid using the term ecosystem function altogether in this book. This practice conforms to that adopted by the Millennium Ecosystem Assessment (MA 2005) and by the more recent United Nations initiative, The Economics of Ecosystems and Biodiversity (TEEB 2010). We prefer the word service in this context, because it connotes that there is a provider and a beneficiary, whereas the word function lacks that inference. The word and the notion of ecosystem function is widely entrenched in discourses pertaining to ecosystem services, their benefits as perceived or enjoyed by people, and the values assigned to ecosystem services by economists and social scientists. Interested readers are warmly referred to the TEEB study for a more thorough consideration of the topic, and especially to de Groot et al. (2010), which is the first chapter in the TEEB study's foundational report.
The basic unit of ecology, and thus of ecological restoration, is an ecosystem. An ecosystem is a prescribed unit of the biosphere that consists of populations of living organisms that interact with each other and with the physical environment that sustains them. A. G. Tansley (1935), who first coined the term, described an ecosystem as "the whole system, including not only the organism complex, but also the whole complex of physical factors forming what we call the environment." The living organisms in an ecosystem—plants, animals, and microbial forms of life—collectively comprise its biota. The abiotic (nonliving) infrastructure of an ecosystem, consists of the physical environment, such as the substrate or soil, nutrients, water in all forms and its ionic salt content, and of energetic processes and their results, such as hydraulic movements, climatic expressions, and fire regimes. The distinction between the biotic and abiotic components of an ecosystem is more pedantic than real, because organisms and inert materials are constantly interchanging or altering each other as they participate in tight feedback loops. For example, soil formation is governed by numerous interactions between living organisms, dead organic matter, water, atmospheric gasses, and the mineral substrate. Likewise, the microclimate associated with an ecosystem is the product of biota influencing the regional climate on account of transpiration, shade, and wind reduction.
Ecosystems are generally circumscribed to display a measure of internal consistency with regard to their species composition, community structure, and abiotic features. The biota is usually subdivided into recognizable biotic communities, such as the plant community, the soil microorganism community, or the zooplankton community. Species with shared traits within a given community are designated as functional groups or guilds.
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Table of Contents
About the Society for Ecological Restoration iii
List of Virtual Field Trips xv
Foreword Paddy Woodworth xvii
Part I Why We Restore 1
Chapter 1 Overview 3
Some Basic Terms and Concepts 6
Chapter 2 Values and Ecological Restoration 15
Ecological Values 19
Personal Values 20
Socioeconomic Values 22
Cultural Values 24
Holons and Realms of Organization 27
Chapter 3 Disturbance and Impairment 33
Ecosystem Response to Disturbance 35
Degradation, Damage, Destruction 38
Ecological Consequences of Impairment 39
Part II What We Restore 71
Chapter 4 Recovery 73
Ecological Views of Recovery 78
Ecological Theory and Restoration 85
Chapter 5 Ecological Attributes of Restored Ecosystems 89
Species Composition 90
Community Structure 99
Abiotic Environment 101
Landscape Context 102
Ecological Functionality 104
Historic Continuity 105
Ecological Complexity 106
Biosphere Support 110
Goals and Project Standards 111
Chapter 6 Semicultural Landscapes and Ecosystems 113
Culturalization of Landscapes 115
Examples of Semicultural Landscapes 118
Selecting Semicultural Targets for Restoration 122
Part III How We Restore 135
Chapter 7 Ecological References 137
Reference Concept 137
Types of Reference Sites 141
Steps in Reference Model Preparation 144
Temporal References 149
References in Landscape Restoration 150
Chapter 8 Approaches to Restoration 155
Intensity of Effort 155
Framework Approach 163
Sources of Knowledge 163
Chapter 9 Project Planning and Evaluation 169
Guidelines for Restoration 170
Strategies and Designs 177
Inoculating Soils and Substrates 180
Project Evaluation 181
Part IV Ecological Restoration as a Profession 197
Chapter 10 Relationship of Restoration to Related Fields 199
Restoration Ecology and Ecological Restoration 200
Ecosystem Management 202
Rehabilitation, Reclamation, Revegetation, and Remediation 203
Compensatory Mitigation 206
Fabrication and Creation 207
Landscape Architecture and Design 208
Ecological Engineering 209
Restoration of Natural Capital 212
Sustainability Science 216
Chapter 11 Projects and the Professional 217
Project Sponsors 218
Project Roles 219
Organizational Structure 224
Evolution of Contexts 230
Stewardship Models 233
Practitioner Certification 233
Chapter 12 Moving Restoration Forward-Together 239
Perceptions of Ecological Restoration 240
Novel Ecosystems 243
Climate Change 246
Moving Forward 249
References Cited 267
About the Authors and Collaborators 289