Foundations of Restoration Ecology

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

• Publisher: Island Press
• Year: 2016
• Topic: Biological Sciences
• Print ISBN:
  9781610916974
  9781610916967
• Subtopic: Ecology
• eBook ISBN:
  9781610916981
• Index: Biological Sciences

The practice of ecological restoration, firmly grounded in the science of restoration ecology, provides governments, organizations, and landowners a means to halt degradation and restore function and resilience to ecosystems stressed by climate change and other pressures on the natural world. Foundational theory is a critical component of the underlying science, providing valuable insights into restoring ecological systems effectively and understanding why some efforts to restore systems can fail. In turn, on-the-ground restoration projects can help to guide and refine theory, advancing the field and providing new ideas and innovations for practical application.

This new edition of Foundations of Restoration Ecology provides the latest emerging theories and ideas in the science of restoration ecology. Fully one-third longer than the first edition and comprehensive in scope, it has been dramatically updated to reflect new research. Included are new sections devoted to concepts critical to all restoration projects as well as restoration of specific ecosystem processes, including hydrology, nutrient dynamics, and carbon.  Also new to this edition are case studies that describe real-life restoration scenarios in North and South America, Europe, and Australia. They highlight supporting theory for restoration application and other details important for assessing the degree of success of restoration projects in a variety of contexts. Lists at the end of each chapter summarize new theory introduced in that chapter and its practical application.

Written by acclaimed researchers in the field, this book provides practitioners as well as graduate and undergraduate students with a solid grounding in the newest advances in ecological science and theory.

PART I

Introduction to Restoration and Foundational Concepts

Chapter 1

Ecological Theory and Restoration Ecology

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

Rather than explaining ecosystem structure and function under a single “unified theory,” ecologists deploy a strong and diverse body of theory to address a wide range of ecological problems (Weiner 1995; Pickett et al. 2007; Hastings and Gross 2012). Theories come in many forms—predictive statements, explanatory concepts, and mathematical and computational models (Scheiner and Willig 2011); yet all share a focus on causal explanation. In restoration, theories help to explain historical events, understand current observations, and predict future states. This last application is particularly important because ecosystems, and the task of restoring them, take place in an increasingly altered world (Steffen et al. 2015). Grounded in theory and empiricism from the ecological sciences, restoration ecology provides the science essential to the practice of ecological restoration, which in turn can be used to test those theories in real world contexts (Palmer and Ruhl 2015; Suding et al. 2015).

What Is Restoration Ecology?

Population, community, and ecosystem ecology are well-established branches of ecological science that focus on specific levels of organization, while restoration ecology is much younger and more comprehensive. As “the study of the relationships among organisms and their environment in a restoration context,” restoration ecology draws on all branches of ecological science and spans genes to entire landscapes (Falk et al. 2006). The homology with the general definition of ecology is not coincidental; restoration ecology can be thought of as a special domain of ecological research, defined by context. Typically, this context includes a natural system of some kind that has been altered in composition, structure, or function. The central aim of restoration ecology is thus to describe and quantify those departures from a characteristic ecosystem state (including the full range of spatial and temporal variation), understand what drives and regulates them, and then project how the system can be moved back toward a less disturbed state (Hobbs and Suding 2009). Restoration ecology also integrates a number of related disciplines, including hydrology, geomorphology, oceanography, and others, particularly various social science disciplines.

Ecological theories can inform the design, implementation, and assessment of restoration projects that range in area from small sites to watersheds. Conceptual theories tend to be the broadest, such as the theory of evolution by natural selection, or models of macroecology (chaps. 3, 15, and 16). Other theories may be specific to a particular type of ecosystem or group of organisms, such as biogeo-chemical cycling, community assembly, or disturbance ecology (Young et al. 2001; chaps. 2, 9, 12, 13). Theories that employ mathematical or statistical models may take the form of simple equations derived from first principles or complex sets of equations drawn from extensive empirical observations. For example, a recent set of theoretical models links a wide range of organism and community traits on the basis of energetics (Schramski et al. 2015). Predictions from models can be very general: for example, that restoring large or well-connected parcels of land will enhance restoration of biodiversity (Tambosi et al. 2014; chap. 4). They can also be specific to a particular time period or ecological system; for example, restoring seagrass in Middle Tampa Bay (FL) to levels observed in the 1950s requires reducing chlorophyll below some threshold (Sherwood et al. 2016), and restoring grasslands benefits from relating plant functional diversity to nutrient cycling and soil carbon (Bach et al. 2012).

Theories provide us with templates and logic paths for predictions. Theories are used to guide the framing of research questions, the design of experiments, collection of data, and ways to organize information to understand the natural world. Theories can be used to explore the impacts of assumptions we might make about ecosystems, and deviation from theories can help inform future research. For all of these reasons theory is fundamental, not only to restoration ecology but to the practice and advancement of ecological restoration.

What is Ecological Restoration?

The Society for Ecological Restoration (SER 2004) defines ecological restoration as, “the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed.” Restorationists attempt to move the composition, structure, and dynamics of a damaged system to an ecological state that is within some acceptable limit relative to a less altered and (probably) more sustainable system (Falk 1990; Allen et al. 2002). Informed by the work of Clewell and Aronson (2013), we simplify the SER (2004) framework and attributes of restored systems to define science-based ecological restoration as in Palmer and Ruhl (2015) (table 1–1).

In this simplified framework, features refer to the structural components of an ecosystem. For example, floodplains are a key component of river ecosystems; their connection to the water and land is an aspect of pattern. Similarly, the structure of a forest includes tree size classes and canopy properties; one aspect of its pattern is the spatial distribution of trees on the landscape. Processes (also called functions) include a wide range of dynamic attributes, such as primary production, stream discharge, fire regimes, dispersal and migration, population dynamics, and biogeochemical cycling. Processes vary over time and space, and ideally lead to recovery of a self-sustaining dynamic system that requires less human intervention than during the process of restoration (Beechie et al. 2010).

TABLE 1-1.

Three essential attributes of intact ecosystems that ecological restoration projects aim to recover. Projects are informed by, and also contribute to, a diverse range of ecological theory.
Attributes of Restored Ecosystems and Ecological Theory	Explanation	Relevant Ecological Concepts and Theory
Biological assemblages are characteristic of a reference system of similar type.	Assemblage refers to the identity, relative abundance, and functional attributes of co-occurring taxa. References are relatively undisturbed systems where assemblages are within the historical range of variability.	Trait-based theories Functional ecology Diversity indices Species range limits and controls on abundance Community assembly and succession Cross-scale spatial heterogeneity
Features and processes are needed to sustain the characteristic biological assemblages and support ecological functions are present.	Features include local habitat and system-level structure and spatial pattern in the watershed or landscape that are within the range of variability of reference sites. Processes include dynamic functions characteristic of the system that are necessary to the maintenance of the assemblages and features.	Relationship of biodiversity to ecosystem functions (BEF) Biogeochemical cycles Hydrologic dynamics Ecosystem engineers Disturbance regimes Dispersal, migration theory
Restored system has the potential to be self-sustaining.	Self-sustaining systems require little or no human intervention or maintenance over the long term, in part due to suitable landscape and environmental contexts and exchanges of organisms, matter and energy.	Range of variability Metapopulation dynamics Ecological resilience Stability theory (alternative states, tipping points) Nonlinear dynamics and feedbacks Landscape and spatial ecology

The framework for defining ecological restoration specifies that it “aims to” recover the properties of an intact system such as species assemblages, food webs, and functional attributes similar to reference systems (chaps. 7, 8, 9, and 11). However, restoration can take decades, and even when a design is science based, unexpected alternative states or incomplete recovery may result (chap. 2). An unexpected outcome is different from knowingly targeting an end state other than full ecosystem recovery and fidelity to an appropriate reference system (Clewell 2000; Egan and Howell 2005). Attempts to reverse environmental degradation that are not ecological restoration include the use of hardscapes or nonnative species to reduce excessive soil erosion and run-off, and other types of engineered systems that cannot be self-sustaining given their design or placement in a highly modified landscape context, such as strip mines, chemically polluted brownfields, or severely eroded sites (Palmer and Ruhl 2015). Other examples of projects with limited objectives (Suding et al. 2015) include maximizing a single ecosystem service, such as stabilizing a steep slope using a monoculture of nonnative, deep-rooted trees (Mao et al. 2012), or postmining reclamation of a formerly forested region to a nonnative grassland (Yeiser et al. 2016). So long as objectives are not too narrowly focused (e.g., on a single social goal), recovering a broad range of ecosystem services is possible and the chances of this may be increased if efforts are invested in maximizing functional biodiversity and associated ecological processes (chap. 3).

A “fully restored” ecosystem is inferred to be self-sustaining and resilient; that is, it has the capacity for recovery from expected change and stress (SER 2004). In cases where landscape-scale processes no longer occur naturally, restoration can compensate for some constraints on self-sustainability by reintroducing the missing process (chaps. 4 and 16). Examples include controlled burning to restore grasslands or forests, and flood pulsing to restore riparian habitat and stream channels. Moreover, invasion by an aggressive nonnative species or an uncharacteristic disturbance may trigger the need for ongoing maintenance (Shaish et al. 2010; Dickson et al. 2014). In such cases, “restoration” sensu stricto may never be finished. It is uncertain whether fully restored ecosystems will be resilient to all future stressors, especially with changing climate and other stressors that occur at a greater rate or magnitude than the system has experienced over recent evolutionary time (chaps. 5, 6, 15, and 17).

The Restoration-Theory Linkage

The acid test of our understanding is not whether we can take ecosystems to bits on paper, however scientifically, but whether we can put them together in practice and make them work.—A. D. Bradshaw (1983)

Restoration ecology and ecological restoration are reciprocal concepts. Ecological theory informs the practice of restoration but the converse is also true: restoration science and practice can contribute to basic ecological theory (Bradshaw 1983; Jordan et al. 1987; Perring et al. 2015). Ecological restoration is especially useful for testing theories associated with understanding the processes that govern ecosystem trajectories (assembly rules, postdisturbance succession, alternative stable states; chaps. 2, 8, and 9). For example, work in Poland showed that restoration of drained fens may result in communities with different levels of plant functional diversity due to the differential effects of competition and habitat filters (Hedberg et al. 2014). This work demonstrated that knowing which filters act in a particular setting is essential to predicting which species or functional groups are likely to dominate (chaps. 3, 6, and 9). Efforts to restore natural fire regimes in forested communities have informed general understanding of fire ecology where disturbance dynamics have been disrupted (Falk et al. 2011; Young et al. 2015). Restoration studies have informed our understanding of the link between biodiversity and habitat heterogeneity or complexity (Bell et al. 1997; Zedler 2000; Palmer et al. 2010; chap. 10). Because restoration scientists work, by definition, in systems that have been disrupted, their o...

Table of contents

• Cover
• Title Page
• Copyright
• Contents
• Foreword
• Preface
• Book Guide
• Acknowledgments
• Part I. Introduction to Restoration and Foundational Concepts
• Part II. Ecological Theory and the Restoration of Populations and Communities
• Part III. Ecosystem Processes and Restoration Ecology
• Part IV. The Spatial and Temporal Dimensions of Restoration
• Part V. Synthesis and Challenges
• About the Editors
• About the Contributors