The pace, intensity, and scale at which humans have altered our planet in recent decades is unprecedented. We have dramatically transformed landscapes and waterways through agriculture, logging, mining, and fire suppression, with drastic impacts on public health and human well-being. What can we do to counteract and even reverse the worst of these effects? Restore damaged ecosystems. The Primer of Ecological Restoration is a succinct introduction to the theory and practice of ecological restoration as a strategy to conserve biodiversity and ecosystems. In twelve brief chapters, the book introduces readers to the basics of restoration project planning, monitoring, and adaptive management. It explains abiotic factors such as landforms, soil, and hydrology that are the building blocks to successfully recovering microorganism, plant, and animal communities. Additional chapters cover topics such as invasive species and legal and financial considerations. Each chapter concludes with recommended reading and reference lists, and the book can be paired with online resources for teaching. Perfect for introductory classes in ecological restoration or for practitioners seeking constructive guidance for real-world projects, Primer of Ecological Restoration offers accessible, practical information on recent trends in the field.
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About the Author
Karen D. Holl is a professor of environmental studies at the University of California, Santa Cruz, where she has taught ecological restoration for over 20 years. She conducts research in the rainforests of Latin America and the chaparral, grassland, and riparian systems in California. She is an Aldo Leopold Leadership Fellow, a Fellow of the California Academy of Sciences, and a co-winner of the Theodore Sperry Award of the Society for Ecological Restoration.
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Why Restore Ecosystems?
The enormous extent of human impacts on Earth has caused many to propose that we are now in the age of the "Anthropocene," a human-dominated geological epoch (Crutzen 2002). Humans have influenced ecosystems for thousands of years in many ways, from managing species of agricultural value and altering water flow patterns to irrigate crops to using fire as a tool to clear lands and increase soil fertility. Regardless of previous impacts, the pace, intensity, and scale at which humans have altered the planet in recent decades are unprecedented. At this point, even the most remote locations on Earth have been influenced by anthropogenic climate change and long-distance transport of pollutants, and less than one-fourth of the land area is free of direct human impact (Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services 2018).
These impacts come in many forms. Staggering figures can be cited for the loss of all types of ecosystems in every region worldwide. Human activities have resulted in the destruction of more than 10 percent of the dwindling wilderness in the world between the early 1990s and 2015 (Watson et al. 2016), the transformation of 38 percent of global land area for agriculture (FAO n.d.), and the degradation of many remaining ecosystems by human activities such as logging, overhunting, mining, and fire suppression. Anthropogenic changes to hydrologic patterns have dramatically transformed most rivers and wetlands. Human activities have substantially increased levels of phosphorus and biologically available nitrogen and have resulted in toxic concentrations of many substances in the air and water.
In addition to local and regional impacts, human activities are rapidly increasing concentrations of greenhouses gases in the atmosphere. These gases cause changes in global climate patterns, including increased temperature, altered precipitation, rising sea levels, and an increasing frequency of extreme weather events. Elevated carbon dioxide levels also directly affect plant growth and drive acidification of the oceans.
These local, regional, and global transformations of ecosystems jeopardize human well-being in numerous ways (Potts et al. 2018). Land degradation has direct impacts on public health because the loss of forest, grassland, and wetland ecosystems that filter pollutants from water results in an increasing number of people who do not have access to safe drinking water. Destruction of coastal ecosystems elevates the risk of shoreline inhabitants to increasingly frequent and intense storms and causes increased migration. Land degradation costs the world an estimated $6.3 trillion to $10.6 trillion per year, equivalent to 10 to 17 percent of the global gross domestic product (ELD Initiative 2015). Equally noteworthy is that ecosystem degradation exacerbates income inequity; the rural poor obtain a larger share of their income directly from noncultivated resources, such as firewood, construction materials, fisheries, and other food products, so they feel the effects disproportionately (Potts et al. 2018).
Conserving species, ecosystems, and, ultimately, humans, will require dramatic changes to resource distribution and consumption patterns, as well as slowing the human population growth rate. These vast and pressing topics have been discussed extensively elsewhere. One important complementary strategy to counteract the extensive human impacts on the natural world is to restore damaged ecosystems.
Motivations for Restoration
The term ecological restoration is used in different ways (chap. 2) but most commonly is defined as the "process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed" (Society for Ecological Restoration Science and Policy Working Group 2004). Ecological restoration is driven by a diverse and overlapping set of reasons (table 1.1; Clewell and Aronson 2006, 2013).
Most ecological restoration projects are motivated, at least in part, by a desire to bring back species, ecosystems, or ecosystem processes (e.g., nutrient cycling, primary productivity, seed dispersal) that have been compromised by human activities. Increasingly, restoration projects are prompted by an attempt to mitigate for and adapt to climate change. Forest, wetland, and grassland restoration can increase carbon storage and, along with aggressive efforts to reduce carbon emissions, can help reduce global temperature increase. Restoration of coastal ecosystems, such as mangroves and coral reefs, is a cost-effective way to reduce risks from storms (Asian Mangrove case study). Ecological restoration can help humans and ecosystems adapt to climate change in various ways, such as providing refugia for climate-sensitive species and improving the resilience of crop production to climate variability (Locatelli et al. 2015).
Ecological restoration provides extensive economic benefits to humans through ecosystem services, which are the suite of benefits that ecosystems provide to humanity (Millenium Ecosystem Assessment 2015). They range from supplying people with food, medicines, and fuel to providing important functions such as water purification, flood control, and crop pollination. They are goods and services that the natural world has always provided to humans, but that we have frequently overlooked until after ecosystems are destroyed or degraded. Restoring an ecosystem is often a less expensive option to provide humanity with specific services than trying to provide the service with a heavily engineered solution. For example, Ferrario et al. (2014) found that on average the cost of installing seawalls and breakwaters was at least ten times more expensive than restoring reefs to provide storm protection to coastal cities. Moreover, some ecosystem services are simply irreplaceable at any cost. Whereas engineered structures may substitute for the coastal erosion control services that reefs provide, they do not provide the recreational values of people who visit reefs, cultural values of indigenous groups that have relied on reefs for fisheries for generations, and the biodiversity hosted in reefs that might provide compounds for pharmaceuticals.
Some restoration projects are funded as job creation and training programs to provide direct economic benefits. For instance, the Working for Water Project in South Africa has employed approximately 10,000 workers yearly between 1996 and 2012 on projects to remove invasive nonnative trees and shrubs that reduce water supply; this program has been driven largely by the government's aim to increase rural employment (van Wilgen and Wannenburgh 2016).
A host of social and cultural factors also motivate restoration projects (Clewell and Aronson 2006; Egan, Hjerpe, and Abrams 2011). Many restoration projects are led by individuals and community groups who want to restore a local ecosystem because of a sense of connection to the land or for aesthetic reasons (Dolan, Harris, and Adler 2015). Restoration can provide opportunities for place-based education for learners of all ages; as such, a growing number of restoration curricula are available that integrate science standards with hands-on restoration experiments. Such local projects may offer participants an opportunity for spiritual renewal and to atone for damages caused by humans (Jordan 2003). Likewise, some projects, particularly those involving indigenous groups, focus on restoring cultural values, such as replanting or managing for certain traditional plants used by indigenous groups for food or basketry (Uprety et al. 2012).
The need to compensate for past human damage to ecosystems — combined with the ecological, economic, and social benefits of restoration — has resulted in a host of legislative mandates to fund or require restoration (chap. 11). In many countries, laws require mining companies to restore or reclaim lands after mining is completed. In some countries, laws target restoration of specific ecosystems, such as wetlands in the United States.
Together, these motivations have resulted in calls for the restoration of hundreds of millions of hectares of land at the global scale. It is important to recognize that even within individual restoration projects, different people and organizations are motivated to restore for different reasons. Hence, discussing and aiming to meet different goals and desires is a critical part of the planning process (chap. 3; Gann et al. 2019).
Restoration as One Component of Conservation Efforts
Ecological restoration is one of a suite of strategies to conserve biodiversity, ecosystems, and the services these ecosystems provide to humans. Clearly, protecting and maintaining minimally impacted ecosystems should remain at the core of conservation practice given that many research projects and case studies show that even the most successful restoration projects restore a subset of the species and ecosystem services present prior to disturbance (Rey Benayas et al. 2009; Moreno-Mateos et al. 2017).
Academics once debated whether humans should intervene to help facilitate the recovery of damaged ecosystems or just allow the ecosystems to recover on their own. Today it is widely recognized that human management to restore ecosystems is an important complementary component of conservation efforts given the intensity and extent of existing human impacts and the need to replace lost ecosystem services to people as quickly as possible. The question is no longer whether to restore ecosystems, but, rather, in what cases and to what extent should we intervene to facilitate ecosystem recovery? In addition, when should we prioritize restoration among the range of conservation actions?
Restoration efforts have been criticized for undermining habitat preservation efforts by offering an opportunity to offset habitat destruction, yet I contend that few, if any, restoration ecologists would suggest restoration as an alternative to habitat preservation. When a person's house is burglarized, a primary concern is to improve security so that the act is not repeated, but improving security does not lessen the need to replace stolen items. Of course, there may be no substitutes for certain items such as photographs or other memorabilia, but the owners normally do their best to re-create the house as it was before the vandalism. Likewise, conservation and restoration are not mutually exclusive; they are complementary actions. In general, the field of conservation biology has become more hands-on in recent years (Hobbs et al. 2011); actions are increasingly taken to maintain existing habitats both proactively (e.g., preventing invasive species from colonizing existing habitats) and reactively (e.g., removing invasive species).
Whereas restoration may mitigate some anthropogenic impacts on the natural world, restoration is a useless exercise unless it is part of an effort to reduce the drivers of habitat conversion, which are complex and vary across the globe (Geist et al. 2006). The human population continues to grow rapidly, having increased by 1.6 billion people between 2000 and 2019, and we are adding approximately 200,000 additional people to the planet each day. Likewise, high levels of consumption in places like the United States and Europe and growing levels of consumption in nations such as China and Brazil increase human impacts on ecosystems. Complex patterns of global trade and rural-urban migration, as well as new technologies, interact to affect land use patterns (Lambin and Meyfroidt 2011). Although a detailed discussion of how to reduce these drivers of habitat degradation and conversion is beyond the scope of the book, it is critical to recognize that ecological restoration has to be a part of multifaceted efforts to conserve ecosystems while providing for human livelihoods. A broad range of approaches is needed not only to conserve and restore ecosystems and species, but also to ensure the survival of the human species that depends on them.
Clewell, Andre, and James Aronson. 2006. "Motivations for the restoration of ecosystems." Conservation Biology 20:420–28.
Discusses a range of motivations for restoring damaged ecosystems.
Egan, David, Evan E. Hjerpe, and Jesse Abrams (eds). 2011. Human Dimensions of Ecological Restoration. Washington, DC: Island Press.
Each chapter of this edited volume addresses different aspects and case studies of human participation in restoration projects.
Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. 2018. Summary for Policymakers of the Assessment Report on Land Degradation and Restoration of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. Bonn, Germany: IPBES Secretariat. https://www.ipbes.net/assessment-reports/ldr.
Summarizes an international effort to provide a current review of the state of the knowledge of land degradation and restoration.CHAPTER 2
Given the many different motivations for restoration (chap. 1) and the broad range of strategies used to restore ecosystems, it is not surprising that definitions of restoration are also broad and variable. In the early years of the field of restoration ecology, there was a strong distinction between the term restoration and other terms describing ecosystem management with different goals. Restoration was used to refer to efforts to restore "predisturbance" or "historical" community composition, ecosystem structure, and ecosystem processes (fig. 2.1). In contrast, other terms, such as rehabilitation, reclamation, and revegetation, described efforts to improve the condition of a degraded ecosystem, typically focusing on specific ecosystem processes and ecosystem services, such as enhancing plant productivity, reducing erosion, or improving water quality, without necessarily striving to re-create a specific community composition (table 2.1; Bradshaw 1984).
Over time, the definition of restoration has continued to evolve and be the subject of extensive debate. The most commonly used definition of restoration in the literature is from the Society for Ecological Restoration (Society for Ecological Restoration Science and Policy Working Group [SER] 2004, 3), namely that ecological restoration "is the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed." Under this definition, the general target of restoration is "a characteristic assemblage of the species that occur in the reference ecosystem and that provide appropriate community structure." The aim is still to set the ecosystem on a trajectory toward recovering community composition, ecosystem structure, and ecosystem processes within the historical range of variability, but there is increasing recognition that even minimally disturbed ecosystems are variable over space and time, so there is not a single endpoint (fig. 2.2; SER 2004; Palmer, Falk, and Zedler 2006). The 2019 SER International Standards for the Practice of Ecological Restoration (Gann et al. 2019), a recent attempt to standardize the terminology, principles, and practices of restoration, defines full recovery as the "state or condition whereby all the key ecosystem attributes closely resemble those of the reference model," recognizing that, in fact, there is a range of states within the natural variability rather than a single static endpoint.(Continues…)
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Table of Contents
Preface Acknowledgments Chapter 1. Why Restore Ecosystems? Chapter 2. Defining Restoration Chapter 3. Project Planning Chapter 4. Monitoring and Adaptive Management Chapter 5. Applying Ecological Knowledge to Restoration Chapter 6. Landform and Hydrology Chapter 7. Soil and Water Quality Chapter 8. Invasive Species Chapter 9. Revegetation Chapter 10. Fauna Chapter 11. Legislation Chapter 12. Paying for Restoration Glossary References List of Case Studies and Other Online Resources About the Author Index