Richard T. T. Forman is the PAES Professor of Landscape Ecology at the Harvard University Graduate School of Design School; among his books is the award-winning Land Mosaics (Cambridge University Press, 1995).

Daniel Sperling is Professor of Civil Engineering and Environmental Science and Policy, and founding director of the Institute of Transportation Studies, University of California-Davis.

Adjunct Associate Professor of Landscape Ecology, Harvard University, Graduate School of Design

The twelve co-authors are: John A. Bissonette (Utah State University); Anthony P. Clevenger (Banff National Park); Carol D. Cutshall (Wisconsin Department of Transportation); Virginia H. Dale (Oak Ridge National Laboratory); Lenore Fahrig (Carleton University); Robert France (Harvard University); Charles R. Goldman (University of California-Davis); Kevin Heanue (formerly U. S. Federal Highway Administration); Julia A. Jones (Oregon State University); Frederick J. Swanson (USDA Forest Service); Thomas Turrentine (University of California-Davis); and Thomas C. Winter (U. S. Geological Survey).

Foundations of Road Ecology

What is the use of running when we are not on the right road?

—German proverb

... great technical advances occurred in the technology of pavement structures and surfacings during the nineteenth century. Almost in their entirety, these advances predated the development of the motorcar.... Communities at last saw an alternative to a life full of mud, stench, dust, and noise.

—M. G. Lay, Ways of the World, 1992

Transportation lies at the core of society. It is what links us together. Both businesses and individuals depend on safe and efficient mobility. In the past century in North America, roads and vehicles have enlarged the spiderweb of our interactions and activities. Now we routinely use vehicles on roads to visit a friend, go shopping, travel to school, or dine out.

Unfortunately, with this dependence on roads and vehicles comes deep and widespread environmental damage. As a result, environmental protection now plays a key role in transportation policy and decisions. Ever-increasing resources are devoted to minimizing the adverse impacts of roads and vehicles on species and ecological systems.

Environmental protection is viewed and approached from many perspectives. The engineer seeks technical solutions and designs technical devices to abate damages. The economist seeks the best use of societal resources and identifies actions that yield the highest return. Legislators and lawyers craft sharply defined rules to preclude certain behaviors. Ecologists emphasize that we are too human centered in our responses and seek to elevate the importance of plants and animals. They seek to maintain the diverse characteristics and services of intact, or undegraded, nature and to maintain or reestablish relatively natural ecological systems in human-imprinted areas. Meshing this goal with the economic and social activities of our busy highways remains a daunting challenge.

In market economies, prices are a primary mechanism for allocating resources and guiding behavior. Environmental impacts remain largely outside the marketplace. When we drive a car, we degrade the quality of everyone's air. But we do not pay for damage to health or vegetation. If we did, we would probably pollute less. Although conceptual models exist, no effective mechanism in society ensures a proper balance between supply and demand for clean air. The same basic problem exists for noise and water pollution, climate change, aesthetics, loss of wetlands, and loss of biological diversity. The absence of a pricing mechanism has led to regulatory approaches.

Environmental protection is complex yet more easily regulated in transportation than in most other sectors of society because transportation networks are mainly in the public domain. Governments at various levels build and maintain most roads and largely own, operate, and subsidize transit services. Governments also own and manage many ecologically important lands where public roads exist (Figure 1.1). Entwinement of transportation with the public domain means that public goals, such as environmental protection, play a more direct role in investments and institutional behavior. Public pressure can translate directly into action by elected leaders and public officials.

Environmental protection came to the forefront of public discourse in the 1960s. Such environmental disasters as London's "killer smog," which killed scores of people, and the Cuyahoga River in Ohio (USA), which caught fire, galvanized worldwide attention. The realization that newly developed and widely used chemicals could decimate ecosystems and poison humans on an extensive scale, a discovery highlighted by Rachel Carson's Silent Spring, catalyzed public action.

In the transportation sector, air pollution proved the initial and most compelling call to action, first in California and then elsewhere. Widespread pollution in the USA culminated with the federal 1970 Clean Air Act, which accelerated the process of eliminating lead from gasoline and reducing vehicular pollution. This law was followed in the mid-1970s by fuel economy rules and "gas guzzler" disincentives. Japan pursued roughly the same track in reducing emissions and fuel consumption, as did Western Europe somewhat later.

In a larger sense, many nations were becoming more environmentally conscious as the 1960s ended. Rules and laws were passed to reduce noise and decrease air and water pollution. Greater concern for aesthetics was emerging. In the USA, the National Environmental Policy Act (NEPA) became law, which required that environmental impacts be documented for new projects using federal funds. By the 1970s, environmental and aesthetic concerns were beginning to play an important, if not always well informed, role in the design, construction, and operation of roads.

But even as environmental consciousness evolved, knowledge and political will lagged. As one concern was addressed, another would emerge. As road-side aesthetics received greater emphasis, concerns about non-native and invasive species grew. A phalanx of new rules and institutions emerged to control a carefully specified set of air and water pollutants. But new threats from new pollutants kept appearing. As four-wheel-drive and other high-clearance vehicles tended to replace cars, remote natural areas became accessible to recreational vehicles, and telecommuting from rural areas gained appeal, the threat to ecologically sensitive land increased.

Furthermore, environmental impacts have become global in nature, through the cascading accumulation of ecological stresses and altering of ecological interactions of the earth system itself. The pervasiveness of roads and their cumulative effect on the environment are now of increasing concern for habitat fragmentation, rare species, and aquatic ecosystems.

What Is Road Ecology?

In 1994, a lone ecologist slowly drove a long, winding road up a canyon in the Rocky Mountains. Front views, like an ancient movie, flashed back and forth from towering granite cliffs to precipitous forest slopes. The road, an engineering...