Foundations of Restoration Ecology

Donald A. Falk, Margaret A. Palmer, Joy B. Zedler, Donald A. Falk, Margaret A. Palmer, Joy B. Zedler

• Publisher: Island Press
• Year: 2013
• Print ISBN:
  9781597260176
  9781597260169
• eBook ISBN:
  9781597266048
• Topic: Biological Sciences
• Subtopic: Ecology
• Index: Biological Sciences

As the practical application of ecological restoration continues to grow, there is an increasing need to connect restoration practice to areas of underlying ecological theory. Foundations of Restoration Ecology is an important milestone in the field, bringing together leading ecologists to bridge the gap between theory and practice by translating elements of ecological theory and current research themes into a scientific framework for the field of restoration ecology.

Each chapter addresses a particular area of ecological theory, covering traditional levels of biological hierarchy (such as population genetics, demography, community ecology) as well as topics of central relevance to the challenges of restoration ecology (such as species interactions, fine-scale heterogeneity, successional trajectories, invasive species ecology, ecophysiology). Several chapters focus on research tools (research design, statistical analysis, modeling), or place restoration ecology research in a larger context (large-scale ecological phenomena, macroecology, climate change and paleoecology, evolutionary ecology).

The book makes a compelling case that a stronger connection between ecological theory and the science of restoration ecology will be mutually beneficial for both fields: restoration ecology benefits from a stronger grounding in basic theory, while ecological theory benefits from the unique opportunities for experimentation in a restoration context.

Foundations of Restoration Ecology advances the science behind the practice of restoring ecosystems while exploring ways in which restoration ecology can inform basic ecological questions. It provides the first comprehensive overview of the theoretical foundations of restoration ecology, and is a must-have volume for anyone involved in restoration research, teaching, or practice.

Chapter 1

Ecological Theory and Restoration Ecology

MARGARET A. PALMER, DONALD A. FALK, AND JOY B. ZEDLER

Ecological restoration has been practiced in some form for centuries. For instance, many indigenous peoples tended lands to sustain natural ecosystem services, such as production of basket-weaving materials, food crops, or forage for game animals, and they continue to do so (Stevens 1997). Today, the practice of ecological restoration is receiving immense attention because it offers the hope of recovery from much of the environmental damage inflicted by misuse or mismanagement of the Earth’s natural resources, especially by technologically advanced societies (Economist 2002; Malakoff 2004).

Strictly speaking, ecological restoration is an attempt to return a system to some historical state, although the difficulty or impossibility of achieving this aim is widely recognized. A more realistic goal may be to move a damaged system to an ecological state that is within some acceptable limits relative to a less disturbed system (Figure 1.1). In this sense of the term, ecological restoration can be viewed as an attempt to recover a natural range of ecosystem composition, structure, and dynamics (Falk 1990; Allen et al. 2002; Palmer et al. 2005). Correspondingly, restoration ecology is the discipline of scientific inquiry dealing with the restoration of ecological systems.

The simplest restorations involve removing a perturbation and allowing the ecosystem to recover via natural ecological processes. For example, a small sewage spill to a large lake might correct itself, if microorganisms can decompose the organic matter and the added nutrients do not trigger algal blooms. Locally extirpated species can recolonize sites as habitat quality improves, and the physical structure of communities can begin to resemble the pre-disruption condition.

More often, however, restoration requires multiple efforts, because multiple perturbations have pushed ecosystems beyond their ability to recover spontaneously. For example, restoring streams affected by urbanization often requires new stormwater infrastructure to reduce peak flows, followed by channel regrading and riparian plantings (Brown 2000). For coastal marshes that have been dredged for boat traffic, restoration might involve removing fill, recontouring intertidal elevations, amending dredge spoil substrates, and introducing native plants. In some cases, “restoration” sensu latu is never finished, as some level of maintenance is always needed (e.g., in wetlands dominated by invasive species). Full restoration means that the ecosystem is once again resilient—it has the capacity to recover from stress (SERI 2002; Walker et al. 2002). Yet it is rarely possible to achieve the self-sustaining state because degraded ecosystems typically lack natural levels of environmental variability (Baron et al. 2002; Pedroli et al. 2002) and their resilience is no longer recoverable (Suding et al. 2004).

FIGURE 1.1 Ecological systems are highly dynamic entities. Thus, all attributes of natural systems, including levels of ecosystem processes (dark grey spheres), vary over time and space within a natural window of variability (dashed oval line). Restoration should be attempted when the system attribute moves outside that window of natural variability (mottled grey spheres). Once “restored,” the system is unlikely to be exactly where it was predisturbance. Although this figure is drawn in three dimensions, the true assessment of both reference and degraded conditions is likely to be multivariate. Illustration motivated by Walker and Boyer (1993).

While restoration is sometimes considered an art or a skill that is honed by practice and tutelage (Van Diggelen et al. 2001), science-based restorations are those projects that benefit from the infusion of ecological theory and application of the scientific method. Science-based restorations follow (1) explicitly stated goals, (2) a restoration design informed by ecological knowledge, and (3) quantitative assessment of system responses employing pre- and postrestoration data collection. Restoration becomes adaptive when a fourth step is followed: (4) analysis and application of results to inform subsequent efforts (Zedler and Callaway 2003). Analogous to adaptive management, the corrections that are made to the restoration process should be guided by sound theory and experimentation, not just trial and error.

An unfortunate aspect of ecological restoration as it is commonly practiced today is that the results of most efforts are not easily accessible to others. Despite pleas to report long-term responses (Zedler 2000; Lake 2001), most projects are not monitored postrestoration (NRC 1992; Bernhardt et al. 2005). Informing later efforts is in many ways the most critical element—science, in its simplest form, is the sequential testing of ideas that over time leads to a better understanding of nature.

Ecological Experimentation in a Restoration Context

The focus of this book is the mutual benefit of a stronger connection between ecological theory and the science of restoration ecology. Ecological restoration provides exciting opportunities to conduct large-scale experiments and test basic ecological theory, both of which have the potential to build the science of restoration ecology (Figure 1.2). A fundamental premise of this book is that the relationship of restoration ecology to ecological theory works in both directions: restoration ecology benefits from a stronger grounding in basic theory, while ecological theory benefits from the unique opportunities for experimentation in a restoration context (Palmer et al., 1997). Many examples of this reciprocity are found throughout this book.

Although ecology overall lacks a general unified theory, the field has developed a strong and diverse body of theory addressing nearly every aspect of ecological interactions (Weiner 1995; McPherson and DeStefano 2003). As evidenced throughout the book, this body of theory is highly relevant to both the science of restoration ecology and the practice of ecological restoration (Table 1.1). While ecological restoration has scientific underpinnings, the integration of ecological theory and restoration has been uneven, despite recognition that the practice could be enhanced by such integration (Young et al. 2005).

FIGURE 1.2 The relationship between ecological theory, restoration ecology, and ecological restoration can be viewed in a hierarchical fashion. While there is a very large body of ecological theory (A, unfilled box), only some of it can be directly applied to restoration ecology at the present time (B, grey box). There is thus a demand to extend and develop theory, and the benefits of doing so extend in both directions. Ecological science benefits from the linkage, as does restoration ecology and ecological restoration. There is also a large part of ecological restoration that will never be guided by restoration ecology (C, black box); instead, contextual constraints and societal objectives, such as co-opting natural resources or modifying ecological systems for human use, will determine restoration objectives and potential much of the time.

TABLE 1.1

There is also great potential to enhance understanding of the basic structure and function of ecological systems by using restoration settings to develop and test theory (Bradshaw 1987; Jordan et al. 1987; Palmer et al. 1997; Hobbs and Harris 2001; Perrow and Davy 2002). Indeed, restored sites, or those that are soon to be restored, represent virtual playgrounds for asking how well ecological theories can predict the responses of natural systems.

The opportunity to test ecological theory in restoration sites is exciting; at the same time, ecologists and evolutionary biologists are challenged to use theory to devise experiments that can be conducted in restoration settings. We do not think this limits our inquiry to a reductionist paradigm: as with ecology itself, understanding can progress even when formal hypotheses cannot be framed (Pickett et al. 1994). Even more difficult is the challenge of designing experiments that are workable within a project’s spatial extent, timing constraints, and resources. Finding suitable sites, receptive managers, interested researchers, appropriate ideas to test, and funding to test them—all at the same time and place—is challenging, but feasible and worth the effort. The payoff for the practice of ecological restoration comes in learning how to improve approaches, how to correct errors, how to accomplish desired outcomes, and how to plan future projects.

Can basic ecological abstractions of nature and mathematical models be used to inform restoration practice, given that ecological responses are often context-dependent? We think so. Every step in the restoration process can be informed by existing ecological theory (Table 1.1); however, every attempt to state predictions from theory also indicates the need to expand theory itself. Thus, we ask: Under what circumstances can we grow the science of restoration ecology using existing ecological theory? What issues or settings require an extension of our theories and models or even the development of theories de novo?

The Imperative to Advance Theory

Experience indicates that restoration follows multiple pathways, which means that outcomes are difficult to predict. Part of the difficulty is that restoration takes place across a multidimensional spectrum of specific sites within various kinds of landscapes, and where goals range from highly specific (e.g., enhance the population of one rare animal species) to general (e.g., encourage vegetation to cover bare substrate). The task of developing theory that offers a high level of predictability is akin to figuring out how to grow myriad crops across a heterogeneous continent. If we consider the centuries it has taken agriculturalists to optimize the crops that farmers should grow in one field in one region (e.g., alternate corn and beans or alfalfa within the cornbelt using specified soil amendments, planting, and harvesting protocols), the difficulty of reproducing entire ecosystems on demand becomes understandable. It could take much longer for the science of restoration to achieve predictable results, because there are more ecosystem types and a wider variety of tools. We assert that these conditions create a great need for guidance from ecological theory. For some ecosystems, ecological theory needs to be melded with physical science theory; for example, river restoration must be informed by geomorphic, hydrological, and ecological theory (Wohl et al. 2005; Palmer et al. 2006).

The need to develop a sound theoretical base for ecological restoration is imperative for at least three reasons. First, restoration is a booming business that requires the support of a knowledge base and research innovations (Economist 2002). Billions of dollars are spent annually to restore polluted and sediment-clogged streams (Bernhardt et al. 2005; Hassett et al. 2005) and to reforest lands that have been degraded and fragmented (Lamb and Gilmore 2003). Yet many restoration ...

Table of contents

• ABOUT ISLAND PRESS
• SOCIETY FOR ECOLOGICAL RESTORATION INTERNATIONAL (SER)
• Title Page
• Copyright Page
• Table of Contents
• FOREWORD
• ACKNOWLEDGMENTS
• Chapter 1 - Ecological Theory and Restoration Ecology
• PART ONE - Ecological Theory and the Restoration of Populations and Communities
• PART TWO - Restoring Ecological Function
• PART THREE - Restoration Ecology in Context
• EDITORS
• CONTRIBUTORS
• INDEX
• Island Press Board of Directors