Corridor Ecology: The Science and Practice of Linking Landscapes for Biodiversity Conservation / Edition 1 available in Paperback
Corridor Ecology: The Science and Practice of Linking Landscapes for Biodiversity Conservation / Edition 1
- ISBN-10:
- 1559630965
- ISBN-13:
- 9781559630962
- Pub. Date:
- 06/01/2006
- Publisher:
- Island Press
- ISBN-10:
- 1559630965
- ISBN-13:
- 9781559630962
- Pub. Date:
- 06/01/2006
- Publisher:
- Island Press
Corridor Ecology: The Science and Practice of Linking Landscapes for Biodiversity Conservation / Edition 1
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Product Details
| ISBN-13: | 9781559630962 |
|---|---|
| Publisher: | Island Press |
| Publication date: | 06/01/2006 |
| Edition description: | 1 |
| Pages: | 344 |
| Product dimensions: | 6.00(w) x 9.00(h) x 1.20(d) |
Read an Excerpt
Corridor Ecology
The Science and Practice of Linking Landscapes for Biodiversity Conservation
By Jodi A. Hilty, William Z. Lidicker, Adina M. Merenlender
ISLAND PRESS
Copyright © 2006 Jodi A. Hilty, William Z. Lidicker Jr., and Adina M. MerenlenderAll rights reserved.
ISBN: 978-1-55963-096-2
CHAPTER 1
Background: Land-Use Change and Habitat Loss
Habitat loss and associated species loss are primarily a result of the acceleration of land-use changes begun over the past century. Therefore, it is important to study land-use change as the root cause of the biodiversity crises. The human population has increased sixfold since the 1800s, and the earth has been transformed to accommodate human habitation and rising consumption (Ehrlich and Ehrlich 2004). A human footprint is detectable across 83 percent of the land area in the world, excluding Antarctica (Sanderson et al. 2002; Figure 1.1). Land-use change associated with human development represents one of the most serious threats to terrestrial biodiversity, along with climate change, nitrogen deposition, and invasive species (Sala et al. 2000).
Cultivation of North America's Great Plains (2.6 million square kilometers [1 million square miles]), for example, has led to the loss of more than 96 percent of its tallgrass prairie (Samson and Knopf 1994), 76 to 82 percent of its eastern mixed grasslands, and 25 percent of its shortgrass prairie (Loveland and Hutcheson 1995). The habitat loss from such land-use change due to agricultural expansion has led to a corresponding loss of biodiversity. In the Great Plains, 465 species are of conservation concern, and endemic songbird and grassland nesting bird species have declined by 50 and 75 percent, respectively (Environmental Protection Agency 2002, Ostlie et al. 1997).
An early attempt to map large undeveloped wilderness areas (greater than 4,000 square kilometers, or about 1,500 square miles) globally estimated that such areas constitute only 16 percent of the land on earth outside the polar regions (McCloskey and Spalding 1989). The paucity of wilderness on earth restricts the space suitable for persistence of some species, especially those that require large ranges. Where wilderness does remain it is often in isolated patches. These isolated patches of natural habitat rarely contain the biodiversity that existed in the region prior to fragmentation. For example, in the Amazon basin, researchers discovered that because of the way species are distributed across the landscape, some species will not be supported in remaining forest fragments (Laurance et al. 2002).
Synergistic effects between habitat loss, habitat fragmentation, and global climate warming (Opdam and Wascher 2004) can compound the effects of habitat loss on biodiversity. For example, researchers are trying to determine whether species will be able to shift their distributions or evolve new adaptations fast enough to accommodate global climate change. Numerous studies document the historical movement of species as climate changed in the past (DeChaine and Martin 2004), but the unprecedented speed of modern climate change combined with habitat loss could make historical processes of adaptation less applicable today. Habitat fragmentation and global warming may not generally present a significant threat to species that currently survive in a diverse array of habitat patches, but species that are isolated in only a few patches or restricted to mountaintops may not be able to rapidly shift their distribution in order to survive climate change (Opdam and Wascher 2004).
Widespread habitat loss and fragmentation due to human activities clearly threatens species survival (Kucera and Barrett 1995). The global rate of species extinction is orders of magnitude higher today than before modern rates of land and water expropriation by human beings. In fact, if the current rate of biodiversity loss continues, we will experience the most extreme extinction event in the past 65 million years (E. O. Wilson 1988). These losses will be devastating for humans, given that we depend on the goods and services that intact ecosystems offer. Many of our medicines and all of our food and fiber, the basis for our economies and our survival, are derived from wild species. Ecosystems are also responsible for many of the natural processes on which we depend, such as maintaining air quality, soil production, and nutrient cycling; moderating climate; providing fresh water, fish and game, and pollination services; breaking down pollutants and waste; and controlling parasites and diseases (Naeem et al. 1994). An interdisciplinary field of study has arisen around trying to understand ecological resilience, which is defined as the capacity of a system to withstand changes to the processes that control its structures (Holling and Gunderson 2002). One of the primary observations is that disturbing ecosystems can reduce their resilience and result in dramatic shifts to less desirable states that weaken their capacity to provide ecosystem goods and services (Folke et al. 2004).
Some scientists have quantified ecosystem services in financial terms (Daily and Ellison 2002). One study estimated that the earth's biosphere provides US$16 to $54 trillion worth of services per year that we currently do not pay for (Costanza et al. 1997). While quantifying ecosystem services may help enlighten people to the importance of natural systems in their daily life, it is difficult to quantify the value to humans of each of the 10 to 30 million or so species inhabiting the earth. The ecological roles of most species are unknown to us, but we do know the key roles that some species play in the normal functioning of biotic communities. For example, if it were not for a few kinds of microorganisms that can digest chiton, the shed exoskeletons of arthropods would bury the surface of the earth. A study of the functional role of species in ecological communities reveals that while multiple species can contribute to ecosystem process and function in the same way, referred to as redundancy (B. H. Walker 1992), ecosystem reliability may depend on that redundancy. In other words, removing species because they are redundant could have consequences (Naeem 1998).
While the cost of species extinction to ecosystems and the goods and services that they provide should be one of today's primary concerns, what motivates many people to conserve nature is the intrinsic value of biodiversity (Rolston 1988). With the loss of biodiversity we are losing important opportunities for personal inspiration and cultural enrichment, whether by bird watching, catching and releasing wild salmon, or simply enjoying a natural scenic view. To ignore the emotional, and for some spiritual, importance of conserving biodiversity and focus solely on the goods and services people rely on is a mistake. We must acknowledge our ethical and moral responsibility to prevent irreversible change to the earth's systems so that we do not harm other species and our own future generations.
Importance and Types of Land-Use Change
Land-use change has received less public attention than other threats to natural systems, such as global climate change and air and water pollution. This is true despite the fact that it is the primary cause of habitat loss and ecosystem degradation and greatly exacerbates most of the other threats to the environment (Harte 2001). For example, the impacts of land-use change on local climate can often be greater than predicted impacts of climate change because changing land cover alters the way the sunlight is absorbed and affects evapotranspiration rates (Lashof et al. 1997). In the Amazon basin, upland land-use change and associated forest loss have resulted in less local rainfall because less water is evaporating into the atmosphere from the rain forest (McGuffie and Henderson-Sellers 2004).
Land-use change has multiple drivers and complex outcomes that generally elude our ability to provide a technical fix for the problems generated. We cannot usually find a single solution to slowing land-use change or reducing its impacts that is as tangible as lowering carbon dioxide emissions to slow global warming, for example.
Given the interactions between human development patterns and the natural systems that support ecological processes and environmental goods and services, it is important that we understand the rates and patterns of land-use change resulting from human development (Tjallingii 2000). Addressing the process and pattern of past land-use change, forecasting future land-use change, and determining the risk of those changes to the environment are important for planning a sustainable future. The first step is to establish a causal relationship between land use and environmental impacts. We do not know the full impacts of land use on biodiversity over time, in part because we do not fully understand ecosystem resilience, the amount of disturbance that an ecosystem can withstand without changing its self-organizing processes and the variables that control its structures (Gunderson et al. 2002).
Land-use changes and the resulting impacts to natural habitats often happen incrementally with seemingly subtle effects. It can be difficult to assess the cumulative effects of those incremental changes, and most environmental impact assessments do not take them into account because analysis is done at the site scale and does not evaluate the potential for larger-scale impacts. This makes it hard to stop land-use change, even if scientists could quantify when thresholds of irreparable damage are crossed. And stopping destructive land use today because of the cumulative impacts of past activities places the entire cost of preventing development or mitigation on a few current operators, which can be politically, ethically, and even legally untenable.
The types of land-use change responsible for converting most natural areas around the world include agriculture, logging, and to some extent mining, and urban and residential development.
Agriculture, Logging, and Mining
The pressure during the Green Revolution, the period of technological development of agricultural practices that began in the 1940s, to increase cereal crop yields through the use of improved crop varieties, fertilizers, pesticides, irrigation, and mechanization led to more intensive agricultural production. Intensive agriculture was encouraged by subsidies and other governmental support measures, such as the Common Agricultural Policy, which established rules and regulations for Europe's agricultural sector beginning in the 1960s. Subsidies were put in place that rewarded farmers according to the volume of crops they produced, creating a strong incentive for high-input, high-output agriculture. As a result, the structure and species composition of agroecosystems were greatly simplified through a reduction in the types of crops grown and the removal of native vegetation in and around the farm to increase production. For example, there is some evidence that this led to declines of farmland birds in Europe (Donald et al. 2001).
In the past fifty years, a widespread movement toward sustainable agriculture has arisen as a backlash against the practices of the Green Revolution. Sustainability rests on the principle that we must meet today's agricultural and economic needs without degrading the natural resources for our future welfare. Sustainable agriculture and the study of agroecology remain primarily focused on practices and systems at the scale of the individual farm. Reforestation, planting hedgerows of native species, reducing the application of fertilizers and pesticides, and maintaining and restoring riparian corridors are treatments employed as part of agri-environment measures.
Some agri-environment programs provide financial incentives for farmers who implement environmentally friendly practices. In Europe, over 20 percent of the agricultural land today is under such programs. These types of incentive programs to restore farmland for environmental benefits are also receiving support in Australia under the Commonwealth's National Action Plan for Salinity and Water Quality (2000) and in the United States through the Department of Agriculture Farm Bill (2002). Also, in 1997, as part of the Conservation Reserve Program, the U.S. Department of Agriculture's Natural Resource Conservation Service developed a "buffer initiative," which promotes the use of contour buffer strips, field borders, grassed waterways, filter strips, and riparian forest buffers across America's farmland. These treatments represent various ways of planting around the farm to increase beneficial insects, filter sediment, slow runoff, and protect water courses. In some case, these linear landscape features can increase habitat connectivity. Recent research in Holland comparing the extent to which fields with and without these features support plant, bird, fly, and bee diversity revealed some benefit to invertebrates but none for plants and birds (Kleijn et al. 2004). There is a prevailing view that these landscape features will facilitate the movement of wildlife between natural areas and increase interbreeding between isolated populations, but that remains relatively untested.
Agriculture is expanding in approximately 70 percent of the countries of the world, and in two thirds of those countries forest area is decreasing (Food and Agriculture Organization of the United Nations [FAO] 2003). While agriculture can clearly result in deforestation, it usually receives relatively little environmental regulatory oversight compared to forestry and commercial and residential development (Giusti and Merenlender 2002, Hobson et al. 2002). This means that environmental impacts such as habitat loss and fragmentation resulting from agricultural expansion are rarely reviewed prior to agricultural land conversion.
The concept of sustainable agriculture needs to go beyond the boundaries of the farm to include larger ecosystems, the myriad of species those systems support, and the goods and services they provide to humans. Enhancing large-scale agricultural landscapes or "farmscapes" for biodiversity conservation represents a new approach to agroecology that recognizes the importance of sustainable agriculture at a landscape scale (Kremen et al. 2002). This approach goes beyond planting and retaining hedgerows and other habitat enhancements and addresses how farmland and wildlands influence one another. For example, researchers demonstrated enhanced pollinator activity in coffee plantations near remnant tropical forest in Costa Rica (Ricketts 2004). The importance of mitigating habitat fragmentation across the larger agricultural landscape has recently been recognized in Europe. To that end European environmental and agricultural policies now address connectivity with ecological networks (Jongman 1995). The establishment of ecological networks across Europe includes identifying core areas, corridors, buffer zones, and areas where restoration is needed to enhance those elements of the network (Jongman 1995).
Logging also continues to be a primary cause of deforestation, with 5.6 million hectares (13.8 million acres) logged globally each year from 1981 to 1990 (FAO 2003). In tropical countries, deforestation is fragmenting the landscape, resulting in an increased number of remnant forest patches within a human-modified matrix (Bierregaard et al. 1992). In some places, especially in the northern latitude locations that were logged more extensively in the past than they are now, forest cover is increasing due to forest regeneration (FAO 2003). In most countries, forestry is regulated, in part for environmental protection. These regulations often include the retention of corridors, especially along water courses, but few generalizations can be made about the design and ultimate utility of these efforts (Bierregaard et al. 1997, Simberloff 2001). Despite some efforts by industry to practice sustainable forestry and maintain connectivity, logging is still one of the primary causes of land-use change, leading to habitat loss and fragmentation in many parts of the world.
Mining and energy resource development can severely affect biodiversity locally and are becoming more of a problem, as well, especially in developing countries. With the assistance of foreign direct investment, mining has increased in sub-Saharan Africa. In Ghana, for example, foreign direct investment primarily for gold extraction increased rapidly from US$15 million in 1990 to US$233 million in 1994 (Boocock 2002). Changes in land use as a result of gold mining in Ghana include loss of farmland and loss of natural habitat within forest reserves (Boocock 2002). The problems of mining activities are well documented and include water and soil contamination, which cause severe health problems for local people (Hilson 2002). Surrounding flora and fauna are, of course, affected, but less appreciated are the diversion of rivers to provide water for mining activities and the increase in roads, both of which have regional environmental consequences.
(Continues...)
Excerpted from Corridor Ecology by Jodi A. Hilty, William Z. Lidicker, Adina M. Merenlender. Copyright © 2006 Jodi A. Hilty, William Z. Lidicker Jr., and Adina M. Merenlender. Excerpted by permission of ISLAND PRESS.
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Table of Contents
Foreword Preface Introduction PART I. Why Maintain and Restore Connectivity? Chapter 1. Background: Land-Use Change and Habitat Loss Chapter 2. Understanding Fragmentation Chapter 3. The Ecological Framework PART II. Key Connectivity Considerations Chapter 4. Approaches to Achieving Habitat Connectivity Chapter 5. Role of the Matrix Chapter 6. Potential Pitfalls of Linking Landscapes PART III. Corridor Design, Planning, and Implementation Chapter 7. Corridor Design Objectives Chapter 8. Identifying, Prioritizing, and Assessing Corridors Chapter 9. Protecting and Restoring Corridors Conclusion References About the Authors Index