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...