Ecological Restoration

Principles, Values, and Structure of an Emerging Profession

Andre F. Clewell, James Aronson

• Publisher: Island Press
• Year: 2012
• ISBN:
  9781610910644
• Topic: Biological Sciences
• Subtopic: Science General
• Index: Biological Sciences

The field of 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.Ecological Restoration offers for the first time a unified vision of ecological restoration as a field of study, one that clearly states the discipline's precepts and emphasizes issues of importance to those involved at all levels. 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 based
-considers the principles of restoration practice
-explores the diverse values that are fulfilled with the restoration of ecosystems
-reviews the structure of restoration practice, including the various contexts for restoration work, the professional developmof its practitioners, and the relationships of restoration with allied fields and activitiesA unique feature of the book is the inclusion of eight "virtual field trips, " short photo essays of project sites around the world that illustrate various points made in the book and are "led" by those who were intimately involved with the project described.Throughout, ecological restoration is conceived as a holistic endeavor, one that addresses issues of ecological degradation, biodiversity loss, and sustainability science simultaneously, and draws upon cultural resources and local skills and knowledge in restoration work.

PART I

Introduction and Essential Background

More than a century ago, the term restoration of mountain lands was already being used by foresters and engineers in southern Europe, but the meaning was quite different from what we think of today as ecological restoration (Vallauri et al. 2002). People then were referring more to what we would call today silviculture and erosion control. Although restoration was bandied about as a notion for recovering the ecological past, until very recently there was no discipline called ecological restoration. In an earlier generation, Aldo Leopold had used the terms restoration and restoring with reference to his attempts to reconstruct habitat and to admonish his contemporaries to become land doctors (Zedler 1999). By the mid-1970s there was a dawning realization that restoration—or whatever it was to be called—was a potential new approach to stemming the ominous trends toward losses of habitat, biological diversity, and natural areas (Bradshaw and Chadwick 1980). By the time of the first annual conference of the Society for Ecological Restoration and Management (now the Society for Ecological Restoration International), held in Oakland, California in 1989, the term ecological restoration and the emerging discipline that this term signified had already jelled. Restoration then meant the recovery of a prior state, and it still does. However, as we became increasingly experienced with restoration work, and as Europeans and others from around the world became engaged in the restoration effort, we began to assume a broader view as to what constituted ecological restoration.

As we were trying to figure out what we meant by restoration, our firm theoretical foundation was trembling beneath our feet. Ecology was undergoing a revolution of sorts as patch dynamics and nonequilibrium theory were being formulated and were replacing the older paradigms of succession, climax, and balance of nature. Added to this milieu was the clamor for environmental preservation, which had been simmering for a century and had erupted into a cultural war in North America between environmental and economic development interests. Among the otherwise solid ranks of the preservationists was a schism that divided those who recognized humans as indistinguishable from nature and those who pursued the ideal of pristine nature in which people could only leave footprints. These crosscurrents swirled as ecological restoration began to take shape. The choppy seas are subsiding but are still not calm as we continue to debate what we mean when we say that we restore ecosystems. A powerful new driver in the debate is the recognition of restoration as an elixir to resolve socioeconomic problems and to institute sustainable economic development, particularly in less affluent regions of the world, and to preserve biodiversity.

This, then, is the backdrop for Part I of this book. Our intention is to identify and assemble the various concepts, contexts, and principles of ecological restoration in a coherent fashion that reflects a global vision for our field. By doing so, we attempt a holistic and realistic overview of ecological restoration that will encourage readers to explore more deeply what ecological restoration really means, how and why we go about accomplishing it, and the promises it offers. We shall also take the reader on the first two of the eight Virtual Field Trips in this book, to Australia and to Chile, in order to illustrate ideas presented in the text.

Chapter 1

Essence of Restoration

Ecological restoration is the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed (SER 2002). From an ecological perspective, it is an intentional activity that initiates or accelerates ecosystem recovery with respect to species composition, community structure, ecological function, suitability of the physical environment to support the biota, and connectivity with the surrounding landscape. From a socioeconomic perspective, ecological restoration recovers flows of natural goods and services of economic consequence that functional ecosystems provide to society. From the perspective of personal and cultural values, ecological restoration renews our relationship with nature in the realms of aesthetics, personal fulfillment, and shared experience and meaning.

A restored ecosystem represents a long-term commitment of land and resources with potential benefits for communities and cultures and for the practitioners who conduct the work. The people who are affected by an ecological restoration project should understand its intent and appreciate its potential value. Otherwise, they may not respect—or protect—the restored ecosystem. For that reason, the decision to restore should enjoy the consensus of stakeholders, financiers, and, to the extent possible, the broader community. Stakeholders should have ample opportunity to contribute to project planning, implementation, and later to the stewardship of the restored ecosystem. The benefits of restoration should be intergenerational and should sustain or improve people’s well-being—whether individual, cultural, or socioeconomic—and their ecological security into the indefinite future.

Ecological restoration returns an ecosystem to a prior state to the extent that the state can be ascertained and then approximated through restoration practice. In this manner, ecological restoration satisfies a profound human desire to recover something of value that was lost. Ecosystems that have suffered only minor degradation or disturbance sometimes can be restored quickly to their apparent former states, perhaps in only a few years. For many other ecosystems, full recovery to an intended target condition may take decades or centuries. For systems that need longer recovery time, the ideal of recovering an ecosystem with historic fidelity must be reconciled with the reality that ecosystems are dynamic and subject to alteration on account of environmental flux and longer-term changes in environmental conditions, and in response to random occurrences in their own dynamic processes. Restored ecosystems can never be static replicas of the past, as if they were paintings, monuments, or dioramic exhibits in a museum. Instead, they respond continuously in biotic expression to their own internal processes and to ever-varying conditions in the external environment.

The role of the restoration practitioner is to reinitiate ecosystem development. The restoration practitioner assists ecosystem recovery much as a physician assists the recovery of a patient. The patient heals himself or herself under the supervision, care, interventions, and encouragement of the physician. Similarly, the ecosystem recovers spontaneously with minimal intervention by a restoration practitioner. The physician cannot guarantee the final disposition of the patient, because healing is ultimately accomplished by the patient. Likewise, the restoration practitioner cannot guarantee the state of the recovered ecosystem, because recovery is ultimately accomplished by the ecosystem.

Ecological restoration necessarily produces a future state of an ecosystem. In Virtual Field Trip 3 and in many other instances, that state may seem like a faithful representation of a prior ecosystem, but to believe it can ever return to that former state—as if time were reversible—is wishful thinking and counterproductive. We invariably restore ecosystems “to the future” within the context and constraints of the present. Because we cannot restore ecosystems to the past, ecological restoration is a metaphorical concept that should not be taken literally. Nonetheless, it is a powerful metaphor that has captured the imagination of people globally.

Once an ecosystem has undergone ecological restoration, it should be self-organizing, self-sustaining, and capable of maintaining 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. It may seem reasonable that a restored ecosystem should be fully self-organizing and capable of self-development, but that is not necessarily the case, for two reasons. First, human-mediated environmental impacts have become so pervasive globally, and so severe locally, that all ecosystems are threatened by transformation if not degradation. These impacts include releases of greenhouse gases that induce global warming, oceanic and atmospheric pollution, acid rain, increases in atmospheric nitrogen, fragmentation of natural landscapes, and colonization by invasive species. Ecosystem management activities must be applied in compensation for these impacts if ecosystem transformations are unacceptable.

Second, many seemingly natural ecosystems coevolved with human inhabitants, whose traditional cultural practices were among the normal ecosystem processes that shaped and maintained those ecosystems. Among cultural ecosystems, intentional burning was the most prevalent traditional practice, and others were important, such as manipulations of community structure associated with harvests of wild plants and animals. Many traditional cultures have been absorbed by modern civilization. The cultural ecosystems that they shaped and tended have suffered consequent degradation. Such ecosystems are candidates for ecological restoration. Once they are restored to their previous condition, traditional cultural practices must be renewed or surrogate practices substituted as ecosystem management. A cultural ecosystem can be self-sustaining only insofar as traditional cultural practices are counted among normal ecosystem functions. In other words, humans belong to ecosystems and participate in ecosystem processes.

Not all traditional cultural practices are ecologically benign. In the long history of our species, we have commonly exploited ecosystems to their ecological detriment in attempts to ensure our own survival and comfort (Diamond 2005). Human-mediated exploitation and abuse of the natural environment have amplified and deflected ecosystem trajectories. Often, ecosystems cannot recover spontaneously and need intensive ecological restoration. In other words, they have crossed one or more thresholds of irreversibility. These thresholds sometimes prevent practitioners from returning an impaired ecosystem to its former state and require that restoration be modeled for new conditions.

However, the future state of the restored ecosystem will not be a novel or synthetic assemblage of organisms that are haphazardly selected. Instead, it will be conceived and organized on the basis of how that ecosystem probably would have evolved on its own in response to contemporary environmental conditions, assuming no impairment. An ecosystem has a developmental trajectory that consists of the chronological sequence of its prior dynamic states. This trajectory can be projected into the future in a predictive manner. The accuracy of that prediction depends on two contingencies. One is the accuracy with which future environmental conditions can be construed. The other is the latitude of expression in ecosystem composition and structure that may result from random events that influence ecosystem development.

The projection of a trajectory into the future is necessarily a probability rather than a certainty, but it improves the likelihood that the restored ecosystem will be resilient and sustainable relative to an entirely synthetic or novel ecosystem that was assembled without a reference model. The projected trajectory serves as the basis for project goals and for the development of a reference model on which project plans are based. This model accepts contemporary realities and anticipates future directions in the developmental trajectory of the historic ecosystem. In this regard, ecological restoration is a holistic endeavor that strives to embrace realities and trends in both culture and the environment from an ecological—rather than a purely engineering or landscaping—perspective.

This vision broadens the conventional meaning of restoration. It recognizes the open-ended nature of ecosystem development throughout time. It acknowledges the magnitude of environmental change that has occurred throughout the world in the last two centuries and, especially, in recent decades. It gives hope that we can continue to enjoy the personal, cultural, and economic benefits of fully functional ecosystems and their biotic grandeur. It suggests that we can undo at least some of the ecological and environmental damage people have done in the past and that despite our ongoing demographic explosion we can clear new paths for cultural and sustainable economic development.

Some Basic Terms and Concepts

Before continuing, we offer background on recurring concepts in this book. This will be essential reading for those who are not familiar with ecology, and it indicates to others our particular points of view in regard to notions that are subject to variable interpretation.

States and Processes

In this book, we distinguish between ecological states and ecological processes (or functions, as processes are alternatively called). A state is the expression or manifestation of an ecosystem in terms of how it appears, as determined by its species composition, community structure, and the sizes and life forms of its prominent species and their spatial configurations. Ecological processes, by contrast, are the dynamic aspects of an ecosystem, many of which can be appreciated only over an ecologically significant period of time. These processes pertain, for example, to the capture and transformation of energy through food webs; the absorption, sequestration, and recycling of nutrients and water; carbon uptake and storage; the differentiation of soils and habitats; the demographic dynamics of species populations; and the myriad interspecific interactions, including competition for resources and symbiotic or mutualistic relationships such as pollination, mycorrhizal associations, and seed dispersal by animals. States and processes are related concepts, though, because an ecological state is necessarily the expression, manifestation, or product of ecological processes.

Ecosystems

The basic unit of ecology, and thus of ecological restoration, is an ecosystem. An ecosystem is a functioning unit of the biosphere of any defined magnitude in space in time, consisting of populations of living organisms that interact with each other and with the physical environment that sustains them. A. G. Tansley (1935:299), who first coined the term, described it 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 make up its biota. The physical environment, which is also called the abiotic (nonliving) environment, consists of the soil or substrate, moisture regime, climatic factors, nutrients, fire cycles, water bodies and their ionic salt content in aquatic environments, and any other physical features and processes that sustain the biota.

An ecosystem is thus any predefined unit of the biosphere that occupies a particular place or geographic location during a particular period of time. Its appearance is the combined expression of various underlying, ongoing processes. It generally displays a measure of internal consistency in terms of its species composition, community structure, and a common physical environment. Species with shared attributes within an ecosystem may be recognized as communities, such as the plant community, the soil microorganismal community, or the zooplankton community. Ecosystem is sometimes used in a collective sense to designate a particular kind of ecosystem that occurs repeatedly, such as riparian forest, alpine tundra, or tidal marsh. Ecosystems are complex, and no two of the same kind are ever alike, particularly at smaller spatial scales. This complexity results from heterogeneity in the physical environment, stochastic (random) variations in ecological processes, and the differential effects of stresses and disturbances on an ecosystem.

Furthermore, ecosystems do not exist apart, as if they were separate, isolated islands...