Sharon K. Collinge, Associate Professor
Safe Passages: Highways, Wildlife, and Habitat Connectivityby Jon P. Beckmann (Editor), Anthony P. Clevenger (Editor), Marcel Huijser (Editor), Jodi A. Hilty (Editor), Richard T.T. Forman (Foreword by)
Safe Passages brings together in a single volume the latest information on the emerging science of road ecology as it relates to mitigating interactions between roads and wildlife. This practical handbook of tools and examples is designed to assist individuals and organizations thinking about or working toward reducing road-wildlife impacts. The book/i>
Safe Passages brings together in a single volume the latest information on the emerging science of road ecology as it relates to mitigating interactions between roads and wildlife. This practical handbook of tools and examples is designed to assist individuals and organizations thinking about or working toward reducing road-wildlife impacts. The book provides:
- an overview of the importance of habitat connectivity with regard to roads
- current planning approaches and technologies for mitigating the impacts of highways on both terrestrial and aquatic species
- different facets of public participation in highway-wildlife connectivity mitigation projects
- case studies from partnerships across North America that highlight successful on-the-ground implementation of ecological and engineering solutions
- recent innovative highway-wildlife mitigation developments
Detailed case studies span a range of scales, from site-specific wildlife crossing structures, to statewide planning for habitat connectivity, to national legislation. Contributors explore the cooperative efforts that are emerging as a result of diverse organizationsincluding transportation agencies, land and wildlife management agencies, and nongovernmental organizationsfinding common ground to tackle important road ecology issues and problems.
Safe Passages is an important new resource for local-, state-, and national-level managers and policymakers working on road-wildlife issues, and will appeal to a broad audience including scientists, agency personnel, planners, land managers, transportation consultants, students, conservation organizations, policymakers, and citizens engaged in road-wildlife mitigation projects.
Gary M. Tabor, Director
"Safe Passages thoughtfully explains the importance of integrating wildlife concerns into the transportation project development process and makes a sound case for working collaboratively to minimize the effects of roads on the natural environment. Don't just read this important book - consider it a call to action to save what we truly treasure."
Mary E. Gray, Environmental Protection Specialist
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Highways, Wildlife, and Habitat Connectivity
By Jon P. Beckmann, Anthony P. Clevenger, Marcel P. Huijser, Jodi A. Hilty
ISLAND PRESSCopyright © 2010 Island Press
All rights reserved.
Connecting Wildlife Populations in Fractured Landscapes
Jon P. Beckmann and Jodi A. Hilty
I see ... an America where a mighty network of highways spreads across our country.
Dwight D. Eisenhower (www.fhwa.dot.gov)
President Eisenhower is credited with leading the creation of the national system of interstate highways across the United States in the 1950s, the primary basis of today's commerce and travel. The system was originally conceived by Eisenhower as a necessary part of defending the country and was called the national highway defense system. He simultaneously touted the importance of the interstate system for communication and the transport of goods. Since its inception, this highway system has continued to grow, with states adding to the network as well as broadening already existing roadways. As of 2008, there were more than 74,000 kilometers (46,000 miles) of roads in the interstate highway network, making it both the largest highway system in the world and the largest public works project in history (U.S. Department of Transportation 2008). During most of the twentieth century, road construction focused on the ease of terrain, soil, and other location considerations along with logistics and cost. It was not until late in the twentieth century that projects started to consider the needs of wildlife in relation to road construction and maintenance (e.g., Forman et al. 2003). As a result, many roadways pass through what were once the best habitats for numerous species, such as in valley bottoms and along streams or rivers.
Today, there are more vehicles on the roads than in the 1950s, and both the technology of roads and automobile design enable vehicles to move faster than in the past. At the same time, many species of wildlife have rebounded in number, such as elk, deer, and other ungulates. Increasing cars and car speeds and increasing numbers of ungulates—the group of animals most commonly reported in accidents—have resulted in more animal-vehicle collisions. These wildlife-vehicle collisions are probably the main reason that society has been increasingly interested in the need to address wildlife-vehicle collisions and the adverse effects roads have on wildlife populations (Trombulak and Frissell 2000, Forman et al. 2003). In 2007,1 to 2 million traffic accidents involving large mammals in the United States caused an estimated US$8.3 billion in vehicle damage (Huijser et al. 2007). In some U.S. states, six to eight cents of every insurance dollar goes toward paying for wildlife-related claims (Lowy 2001). Beyond vehicular damage, an astounding 26,000 people are injured or killed in the United States each year due to vehicle collisions with wildlife (Huijser et al. 2007). According to the Insurance Corporation of British Columbia, the cost to society of a human fatality is C$4.17 million, while an injury costs approximately US$97,000 (Sielecki 2000).
Europeans were first to recognize and start resolving the problem of wildlife-vehicle collisions by commissioning studies of the problem, building wildlife crossings, and reducing traffic speeds to reduce vehicle collisions. In the 1980s, North America saw an increase in interest in studies and construction of wildlife crossings such as those in Florida that are discussed in chapter 10 (Forman et al. 2003). In 2003 the seminal book Road Ecology: Science and Solutions (Forman et al. 2003) formalized this new subdiscipline of ecology. Today, increasing research, general media, and visible projects continue to move the nascent field of road ecology forward. This means that now is the time to bring emerging science, policy, and innovation into standard transportation planning, design, and construction.
Creating projects to minimize or reverse the negative impacts of roads on wildlife, however, is challenging. Given funding constraints and design limitations, it is unlikely that a project will benefit all possible species; therefore, species must be prioritized. Where new roads are being constructed, there are increasing opportunities to consider wildlife early and throughout the decision-making process. Unfortunately, given that many of the mitigation projects for wildlife are for existing roads, most efforts require the daunting task of redesigning roadways to restore connectivity.
This chapter offers a brief review of why roads can be a challenge for wildlife in general; how roads impair connectivity for wildlife populations, including the broader toll of roads on wildlife; and the importance of connectivity. For those interested, many of these concepts are covered in depth elsewhere (e.g., Forman et al. 2003, Hilty et al. 2006), but an overview of these challenges is important in framing the case studies and opportunities presented throughout this book.
The Problem of Roads for Wildlife
Human activities impact much of the world and continue to expand (Sanderson et al. 2002). Rapid population growth, an increase in extractive industries, uncontrolled and unplanned development, and new transportation infrastructure are threatening many of our natural resources and the persistence of wildlife populations (e.g., Western Governor's Association 2008). Many human-made linear infrastructures such as railroads, power lines, and petroleum pipelines intensify habitat degradation (Primack 2006), but roads have the most widespread and lasting impacts (Spellerberg 1998, Davenport and Davenport 2006). Roads serve as the arteries of this ever-expanding human footprint. Networks of roads also inevitably lead to increased human access to areas that were once more remote and undisturbed. Increased access and corresponding impacts can have potentially negative consequences for wildlife. Human activities ranging from logging and petroleum drilling to hiking, camping, and illegal poaching can negatively impact wildlife, and as road networks increase these activities also increase across a much larger expanse of the globe (e.g., Dyer et al. 2002, Roever et al. 2008). This is particularly true when recreational vehicles, such as ATVs and snowmobiles, even further expand human activities into previously remote areas. Roads are also a leading cause of habitat fragmentation and the resulting loss of connectivity for wildlife populations throughout the world, including North America.
The United States alone contains approximately 6.4 million kilometers (4 million miles) of roads, with 4.2 million kilometers (2.6 million miles) of those being paved (Forman et al. 2003, U.S. Federal Highway Administration 2008). Roads now cover more than 1 percent of the total land area within the United States, and roads influence the ecology of at least one-fifth of the land area of the entire country (Forman 1999, Cerulean 2002). In the United States alone, 4.8 million hectares (11.9 million acres) of land have been directly lost due to road construction (Trombulak and Frissell 2000). This means that roads alter ecosystem processes and species distributions. They can also serve as a vector to introduce new, invasive species into adjacent habitats.
The amount of use that roads receive generally corresponds to the level of effects on wildlife. In 1999, approximately 90 percent of all trips taken by Americans were made in vehicles (Turrentine et al. 2001), which equates to more than 200 million vehicles driving 8 trillion kilometers (5 trillion miles) in the United States (Ritters and Wickham 2003). Of all the miles of roads, highways such as the interstate systems have the largest ecological footprint and receive the most use by motorists. Such high-use roads often create the most significant barriers to connectivity between wildlife populations (Transportation Research Board 2002a). Further, traffic speed, as discussed in later chapters, impacts wildlife in that wildlife-vehicle collisions are more likely to occur where automobiles are moving faster, such as on highways.
While the field of road ecology has expanded in recent years to document the consequences of roads on wildlife, relatively little information is available about how wildlife species navigate lands bisected by roadways and how they cross roads (Transportation Research Board 2002, Forman et al. 2003). Such gaps in knowledge impede prudent management and conservation. With increasing awareness and knowledge of transportation's impacts on wildlife, wildlife and land management agencies have the opportunity to make more informed decisions about where and how roads are designed and retrofitted to better accommodate wildlife needs.
Toll of Roads on Wildlife
The development, maintenance, and ongoing use of roads have profound impacts on the world's biodiversity from amphibians and ungulates to birds and even vegetation (e.g., Forman and Alexander 1998). Roads and associated traffic can impact wildlife populations in four ways: (1) decrease habitat amount and quality; (2) increase mortality from collisions with vehicles; (3) limit access to resources; and (4) fragment wildlife populations into smaller and more vulnerable subpopulations (Jaeger et al. 2005).
Decreased Wildlife Habitat Amount and Quality
The creation and expansion of roads decreases existing natural habitat and can lower the quality of remaining habitat adjacent to roads. The area impacted includes the lanes of road and also the area of vegetation that is maintained alongside the road, which can extend anywhere from a meter to 10 or more meters (32.8 feet) away from the edge of the road. The road and associated vegetation management often create an abrupt edge in once continuous habitat, such as creating a clearing in once continuous forest habitat. Physical and biological effects occur at such edge habitats. The edge climate may be warmer and drier, for example, and this can lead to changes in species composition. Depending on the ecosystem type and species, these so-called edge effects can permeate hundreds of meters into adjacent habitat (Reijnen et al. 1995, 1996). Species that are sensitive to edge habitat, especially forest interior species, decrease in density and/or may be less likely to survive due to competition with exotic species, edge predators, and overall poor habitat quality (Laurance 2004, Laurance et al. 2004, Bollinger and Gavin 2004).
In addition to direct habitat loss, road construction can also contribute to indirect habitat loss. Indirect habitat loss occurs where species no longer occupy otherwise sufficient habitat that is adjacent to roads because of behavioral responses to roads (e.g., Berger 2007). For example, researchers have documented that grizzly bears (Ursus arctos horribilis) are less likely to occupy regions with higher road densities (Mattson 1992)
Roads can also be a source of pollution, degrading adjacent core habitat areas. In California, species dependent on nitrogen-poor serpentine soil are negatively affected by car pollution that deposits nitrogen. The introduced nitrogen enables generalist species to out-compete serpentine soil specialists (Weiss 1999). Light and noise are other sources of pollution spilling into nearby habitats. The combination of lighting, noise, runoff of pollutants, and high human activity inhibits the occurrence of big and small species in adjacent habitats (Jaeger et al. 2005). Grizzly bears in the Canadian Rocky Mountains, for example, tend to avoid areas with high vehicle use, traffic noise, and human disturbance (Gibeau et al. 2002, Chruszcz et al. 2003).
Impacts of Vehicle Collisions on Wildlife
Mortality from collisions with vehicles does not appear to pose a significant threat to robust populations, but road mortality can be devastating to small or dwindling populations (Bennett 1991). For example, vehicle-bird collisions are a major source of mortality for endangered Florida scrub jays (Aphelocoma coerulescens) such that road-related mortality is a significant threat to their population (Mumme et al. 2000). In addition road mortality has affected populations of a number of iconic species in North America, including Florida panther (Puma concolor coryi, Maehr et al. 1991), cougars (Beier 1995), pronghorn (Antilocapra americana, Berger et al. 2007), grizzly bears (Gunther et al. 2004), black bears (Ursus americanus, Brody and Pelton 1989, Beckmann and Berger 2003, Hebblewhite et al. 2003, Beckmann and Lackey 2004), and a variety of more common species such as white-tailed deer (Odocoileus virginianus, Widenmaier and Fahrig 2006), raccoons (Procyon lotor, Clark et al. 1989), and red fox (Vulpes vulpes, Hardy et al. 2006). With an estimated 1 million vertebrates killed every day on roads in the United States, death tolls on wildlife are astounding (Lowy 2001). A five-state study concluded that 15,000 reptiles and amphibians, 48,000 mammals, and 77,000 birds die each month due to collisions with vehicles (Havlick 2004).
The presence of roads can be advantageous for some species. For example, some moose (Alces alces) in Grand Teton National Park and surrounding areas appear to benefit from roads. Female moose have begun to realize that humans can be a shield of sorts against one of their major predators, the grizzly bear. Some female moose give birth closer to roads usually avoided by grizzly bears, a behavior that is thought to be a strategy to increase calf survival (Berger 2007). Other species that benefit from roads are scavengers. Increased levels of carrion due to collisions with vehicles have not only benefited ravens (Corvus corax), but other scavengers such as crows (Corpus brachyrhynchos), coyotes (Canis latrans), and turkey vultures (Cathartes aura), to name a few (e.g., Knight et al. 1995). In rare cases, vegetation associated with road right-of-ways may be important to conservation of wildlife, especially in landscapes in which road-associated habitats may be the only natural or seminatural habitat in an otherwise intensely altered landscape (e.g., Huijser and Clevenger 2006). For most species of wildlife, roads are an additional hazard that they must negotiate in an increasingly humanized world.
Roads Limit Access to Resources
Many species require access to different habitats throughout their life cycle or even throughout the year. Species such as salamanders may require ponds or rivers for one part of their life cycle and live another part of their life in terrestrial habitat. Roads that run adjacent to rivers or that circle ponds and lakes either limit movement altogether or can be a major source of mortality for such populations. Other species such as ungulates move from summer to winter ranges. In particularly harsh winters, they may need to move even further to find scarce resources. Roads can impede these migrations. For example, Interstate 80 in southern Wyoming can be a complete barrier to pronghorn migration when animals are trying to move further south to avoid deep snow during severe winters (Berger et al. 2007). In fact, several hundred pronghorn died as a result of their inability to move south of the Interstate 80 barrier during harsh winters in the 1970s and 1980s (Johnson 1988).
Excerpted from Safe Passages by Jon P. Beckmann, Anthony P. Clevenger, Marcel P. Huijser, Jodi A. Hilty. Copyright © 2010 Island Press. Excerpted by permission of ISLAND PRESS.
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Meet the Author
Jon P. Beckmann is an associate conservation scientist for the Wildlife Conservation Society and an affiliated professor at Idaho State University.
Anthony P. Clevenger is a senior wildlife research scientist at the Western Transportation Institute at Montana State University.
Marcel P. Huijser is a research road ecologist at the Western Transportation Institute at Montana State University.
Jodi A. Hilty is director of the Wildlife Conservation Society’s North America Program.
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