From Theory to Practice
E-Book, Englisch, 358 Seiten
ISBN: 978-0-12-407659-4
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark
Christopher Craft is the Janet Duey Professor of Rural Land Policy, O'Neill School of Public and Environmental Affairs, Indiana University, Bloomington and University of Georgia Marine Institute, where he teaches courses in Environmental Science, Applied Ecology, Wetlands Ecology and Restoration Ecology. His introduction to wetland science began in 1983 when, as a new Ph.D. student, he began studying the ecosystem development of tidal marshes that had been created and restored along the North Carolina coast in the 1960s and 1970s. Since that time, Professor Craft has worked on restoration projects in freshwater wetlands of the Florida Everglades, Upper Klamath Lake (Oregon) and the agricultural Midwest, and in estuarine wetlands of the southeast (Sapelo Island, GA), New England and New York-New Jersey harbor. Professor Craft served as President of the Society of Wetland Scientists from 2008-2009. In 2012, he received the National Wetlands Award for Science Research, given annually by the Environmental Law Institute and six U.S. governmental agencies
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1 Introduction
Abstract
Wetlands deliver a number of ecosystem services that benefit people. They provide food and fiber, habitat for plants and animals; buffer waves and floodwaters; remove pollutants; and sequester carbon. They also offer recreational opportunities and a spiritual connection to the natural world. Wetlands worldwide have been lost at an alarming rate, so there is much interest in restoring and creating them. Compared to terrestrial and aquatic ecosystems, wetlands possess unique hydrology, vegetation, and soils/sediments that must be reestablished in order to restore them. It is critical to set preestablished goals prior to restoration. This is necessary because (1) not all wetlands provide the same kinds and intensity of ecosystem services, (2) it may not be possible to restore the environmental template, especially hydrology, needed to reestablish these services, and (3) some services, such as habitat for rare and endangered species and water quality improvement, are not mutually compatible. This book aims to introduce how ecological theory, disturbance, succession, and ecosystem development, can guide restoration efforts and how practices, introducing propagules, amendments and beneficial associations of species, can accelerate development of a fully functioning and self-sustaining ecosystem. Keywords
Alternative stable states; Amendments; Disturbance; Ecosystem development; Ecosystem services; Hydrology; Monitoring; Propagules; Reference wetlands; Soils; Succession; Trajectories; Vegetation; Wetland loss Chapter Outline Why Restore Wetlands? 5 Fundamental Characteristics of Wetlands 7 Setting Realistic Goals 8 Theory and Practice 10 Disturbance: Identifying and Ameliorating Stressors 12 Understanding Ecosystem Dynamics 13 Accelerating Restoration: Succession and Ecosystem Development 13 Reestablishing a Self-Supporting System 15 References 18 Wetlands, where water and land meet, have a unique place in the development of civilization. Rice, a wetland plant, feeds 3.5 billion people worldwide (Seck et al., 2012). Fish, associated with aquatic littoral zones and wetlands, is the primary source of protein for 2.9 billion people (Smith et al., 2010). Rice (Oryza sativa) was first cultivated in India, Southeast Asia, and China (Chang, 1976), and fish were raised among the rice paddies, providing needed protein (Kangmin, 1988). Along the Nile River, early societies were sustained by fish caught from the floodplains and coastal lagoons of the delta (Sahrhage, 2008). Civilization prospered along rivers and deltas of the Yangtze and Yellow Rivers, China; the Irrawaddy, Ganges, and Indus of India; the Nile of Egypt, and the Mesopotamian marshes of Iraq. Later, cities were established where land and water meet, on rivers, lakes, and at the sea’s edge, where they were hubs of transport and commerce. As cities grew, it was convenient to drain or fill the low, wet, swampy, and marshy areas, the wetlands, to expand. With the Industrial Revolution in the eighteenth century and its mechanization of farming and abiotic synthesis of nitrogen fertilizer, large-scale agriculture became feasible. The inevitable result of population growth and the Industrial Revolution was the widespread drainage of freshwater wetlands to grow food crops. Extensive wetlands in regions such as the Midwest US Corn Belt and the interior valleys of California were drained and farmed. Later, large-scale aquaculture, especially shrimp farms, was carved from the extensive mangrove forests of the tropics. During the twentieth century, loss of coastal and freshwater wetlands in temperate regions such as the US, Europe, and China, was extensive. Developing regions of the tropics were not far behind with widespread conversion of mangroves and other wetlands to forest plantations and aquaculture ponds later in the century. Today, the cumulative loss of wetlands in the US, including Alaska, since European settlement is greater than 30% with much greater losses in the Midwest and California where more than 80% of the original acreage has been lost (Dahl, 1990). Worldwide, loss of mangroves, tropical coastal wetlands, is on the order of 20–50% (Valiela et al., 2001; FAO, 2007). In the past 35 years, more than 30% of coastal wetlands and 25% of freshwater swamps in China, where development has been rapid, have been lost (An et al., 2007; He et al., 2014). Delta regions are particularly susceptible to wetland loss as large areas are converted to agriculture (Coleman et al., 2008). Even peatlands are not immune as extractive industries such as peat harvesting and fossil fuel extraction, including oil sands of Canada and fossil fuel extraction in Siberia, eat away at the natural resource. By the 1970s, increasing recognition of the alarming rate of wetland loss led to laws such as the Clean Water Act of 1972 in the US, created to protect the nation’s aquatic resources, including wetlands. A key component of the law was the restoration of degraded wetlands or creation of entirely new ones to compensate for their loss. Today, government programs such as the Wetlands Reserve and Conservation Reserve Programs of the U.S. Department of Agriculture offer financial incentives to restore wetlands. In the Glaciated Interior Plains of the American Midwest, more than 110,000 ha of wetland and riparian buffers were restored between 2000 and 2007 (Fennessy and Craft, 2011). Restoration of freshwater wetlands on former agricultural land has been implemented in Europe and elsewhere to improve water quality and increase landscape diversity (Comin et al., 2001). Wetlands also are created and restored to compensate for their loss from developmental activities such as road building and urban/suburban construction. Globally, while not legally binding, the Ramsar convention encourages protection and restoration of wetlands of international importance (see Chapter 2, Definitions). Whereas the science of wetland restoration is relatively new, people have been restoring for years. The earliest restoration projects were reforestation schemes, planting mangroves for fuel and timber. In Indochina, large-scale mangrove afforestation dates to the late 1800s or earlier (Chowdhury and Ahmed, 1994). Nearly 100 years ago, salt marsh vegetation was planted in Western Europe, the US, Australia, and New Zealand to reclaim land from the sea and to slow coastal erosion (Ranwell, 1967; Knutson et al., 1981; Chung, 2006). At the same time, freshwater wetlands were being reflooded to provide waterfowl habitat (Weller, 1994). This was done by government agencies such as the U.S. Fish and Wildlife Service and by nongovernmental organizations like Ducks Unlimited. These early restoration activities—reforestation, shoreline protection, waterfowl habitat—focused on restoring a particular function such as productivity. Restoration today consists of reestablishing a variety of ecological attributes including community structure (species diversity and habitat) and ecosystem processes (energy flow and nutrient cycling), and the broad spectrum of goods and services delivered by healthy, functioning wetlands. Webster’s Dictionary (http://www.merriam-webster.com) defines restoration as the act or process of returning something to its original condition. In the book, Restoration of Aquatic Ecosystems (1992), the U.S. National Research Council (NRC) defines restoration as the act of bringing an ecosystem back into, as nearly as possible, its original condition. In this book, I expand on the NRC definition to define restoration as the act of bringing an ecosystem back into, as nearly as possible, itsoriginal condition faster than nature does it on its own. This definition contains two key points. Restoration aims to accelerate succession and ecosystem development by deliberate means, spreading propagules, seeds, seedlings, and transplants, and amending the soil with essential nutrients (N) and, sometimes, organic matter. The second point, from the NRC definition, recognizes that often it is not possible to restore a wetland to its original, pre-disturbance condition because stressors that degrade the system cannot be completely eliminated. Many stressors that affect aquatic ecosystems and wetlands, such as flow mistiming, nutrient enrichment, salinity, and other soluble materials (Palmer et al., 2010), originate off-site and propagate downhill and downstream where they cause damage. Other stressors, many related to hydrology, occur on-site and are easier to ameliorate. These include levees, ditches, or placement of spoil atop the site that can be breached, filled, and removed, respectively. This book introduces the science and practice of restoring wetlands: freshwater marshes, floodplain forests, peatlands, tidal marshes, and mangroves. Globally, wetland restoration is driven by policies such as the Ramsar convention on wetlands of international importance, the Clean Water Act of the US, the Water Framework Directive of the European Union, and others. Arguably, the science of wetland restoration, using ecological theory to guide the process, lags behind practice. Wetland restoration, historically, was more of a cut and fit process,...
