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Road Ecology: Science and Solutions. Forman, R. T. T., D. Sperling, J. A. Bissonette, A. P. Clevenger, C. D. Cutshall, V. H. Dale, L. Fahrig, R. France, C. R. Goldman, K. Heanue, J. A. Jones, F. J. Swanson, T. Turrentine, and T. C. Winter. 2002. Island Press, Washington, D.C. 399 pp. $55.00 (hardcover). ISBN 1–55963–932–6. $27.50 (paperback). ISBN 1–55963–933–4.

Ecology has been characterized for several decades by a proliferation of subdisciplines, particularly as ecologists have begun to take serious note of human impacts and to integrate them into research programs. Calls for interdisciplinarity are being heeded and are producing a variety of novel and hybrid approaches to environmental problems. One of the most recent offshoots is “road ecology,” and its first summary volume has been released recently by Island Press. Road ecology is the study of the network of human-built roads and of the relationships between this network and the natural world over which it is spread. Roads turn out to be a decidedly complex subject, calling for a synthetic approach combining concepts and analyses from landscape ecology, network theory, wildlife biology, and toxicology, together with a good deal of conservation biology and a little economics and sociology as well. Reading through this hefty book (399 pages of text), we may be reminded of the extent to which the road network has entered into and defined vast areas of our experience and that of our neighbor species on Earth.

The United States presently contains approximately 6.3 million km of public roads, in addition to an unknown extent of private roads and roads under federal control but closed to the public (including military roads and some roads on U.S. Forest Service land). One of the interesting details to emerge from this book is how approximate our knowledge of the extent of our own road system actually is. Federal Highway Administration statistics may underestimate the mileage of rural roads by as much as 60% because of a lack of data on private road building. Average road density in the United States is estimated at about 0.75 km/km2, but this figure is undoubtedly a significant underestimate because it excludes most private roads, driveways, and parking areas. (By way of comparison, England's average road density is about 1.9 km/km2 and Japan's is closer to 3 km/km2—similar to that of New Jersey.) Roads, together with their rights-of-way, cover more than 1% of the land surface of the continental United States. Canada has a road density of only 0.10 km/km2, but by far the greatest length of roads per capita in the world—almost 20 km per 1000 persons.

Of course, estimates of the length and surface area of a road network do not begin to reflect the ecological footprint of that network. Roads, dissecting the land into a mosaic of variable “mesh size,” alter surrounding flows of materials and energy and patterns of species distribution. Road influences interact with flows of wind and water and behavioral processes to produce a “road-effect zone” of ecological effects extending outward on both sides of the road itself. This zone is really a series of overlapping zones with “asymmetric convoluted margins,” the character of each zone depending on the particular variable of interest. For example, nine ecological factors of interest were mapped and measured around a multilane highway segment in Massachusetts: wetlands, streams, road salt, exotic plants, moose, deer, amphibians, forest birds, and grassland birds. Significant effects on these variables extend anywhere from 100 m to 1 km or more from the road. It has been estimated that 22% of the area of the continental United States is measurably affected in these ways by roads (Forman 1996).

Road Ecology is the product of a collaborative effort involving four transportation specialists, nine ecologists, and a hydrologist. The book ranges from descriptive sections on the construction and engineering of roads, the history of roads, vehicular travel, and transportation planning, to the chemistry of roadsides and impacts of roads on a variety of organisms. Included are discussions of a number of aspects pertaining not strictly to roads but rather to the vehicles that travel on them, such as emissions and global climate change. On the other hand, less is made of the effects on the natural world of the industries that support vehicular traffic. The rise and diversification of the petroleum-based industries, for instance, has been inextricably intertwined with the development of roads. Present and potential work on alternative transportation technologies also receives relatively little attention, although these technologies could arguably alter the terms of the debate in the foreseeable future. But the primary focus of this volume is quite properly the roads themselves, especially their physical and geographical dimensions.

The intended audience could hardly be broader. The list includes transportation professionals, ecologists, planners and policy makers, informed citizens, and students. This has the effect that any particular group may find some sections a bit on the elementary side. But the book gains much more than it loses from its breadth of view.

My principal regret is the lack of attention to tropical areas and the particular issues of road design and construction in developing countries. Perhaps this cannot really be taken as a criticism because the Foreword expressly promises a “North American focus.” And, of course, there is the perennial problem of a lack of reliable data on developing countries. But attention to other parts of the world, especially tropical countries, is sorely needed. Chapter 12 does point out a few of the ways in which road systems in tropical and developing countries differ from those of developed countries, but without elaborating on them. These differences include intensive agriculture in mountainous areas and greater dependence on public transport. Other factors affecting road design and construction in tropical areas include soil profiles, hydrologies, patterns of endemism, ecological zones (especially in montane areas; see, e.g., Young 1994), and patterns of rural versus urban human population density. But perhaps the most important point is that the North American public road network (together with the European, which also receives considerable attention here) is globally exceptional in that it has essentially completed its growth phase and is not expected to continue expanding significantly in extent, although its use continues to expand. Road networks in much of the rest of the world, by contrast, are in a phase of rapid growth, both in extent and in capacity. The section on road history brings out interesting details of the development of the North American system, but many of these details are specific to the geography, political environment, and economic circumstances in which they occurred.

What principles might emerge from this now century-long experience of vehicular road travel? What inferences could be drawn that might predict general aspects of the developmental trajectories of road systems as economies industrialize? How do industrialization processes and the development of the road network interact? Might there not be pitfalls that could be avoided as new road systems grow? A short section in Chapter 13 is devoted to the tropics, discussing the special situation of roads in remote areas and parks, but it does not directly address the issue of explosive current and future system-wide growth and change. A cursory glance at the otherwise extensive and useful index (over 1000 entries) reveals the absence of entries for the following key road-related interests of workers in the tropics: colonization, hunting, bushmeat, market access, ecotourism, industrialization, urban migration, and rural development. Many of these, of course, were crucial issues in earlier phases of the North American network too because they are aspects of a general process of industrialization and urbanization (e.g., Clark 1990; Rothenberg 1992; Foster 1998). In particular, the powerful interconnections between the improvement of roads and the development of market economies can hardly be overstated, and must be considered a principal vector of human influence on habitats and species. Also, I would have liked to find a more explicit review of the ecological effects of road closures. How long it takes a closed or disused road segment to merge back into the surrounding ecological matrix is an interesting question that has not gone unstudied (e.g., Guariguata & Dupuy 1997).

The last chapter stakes a claim for road ecology as “an integral part of sustainable development.” If this is true—and it would be hard to argue against it—the time is now for work on nudging or enticing the oncoming developmental boom in road building and traffic into the least destructive channels possible. At the least, we need to clarify what these channels might be under the specific conditions of rapidly industrializing economies. But perhaps that is material for another book.

An intriguing aspect of this volume is its own developmental history. With their varied backgrounds, the coauthors approached the project with quite different preconceptions. Some thought of roads as an unfortunate correlative of industrial society with overwhelming negative ecological impacts. Others started from the viewpoint that the road system is a highly necessary and basically functional social good, although with some environmental problems. The book mediates successfully between these viewpoints, putting the emphasis on problem solving.

The 14 coauthors are not identified with individual chapters, as is usual in collaborative projects of this sort. Instead, each chapter has gone through a process of writing and rewriting by several authors. One might fear that the writing would emerge from this process as a committee monster, but the chapters are unified in tone and approach, presumably by the dexterous pen of principal author Richard Forman. Each chapter starts off with an imaginative, even poetic, image that introduces and summarizes the following material evocatively and often amusingly. Along the way, these musings provide the reader with a window onto the characteristically synthetic and concrete thinking of the systems-oriented landscape ecologist. The road system and the land as “two giants in uneasy embrace,” the manager of a transportation system as the harried captain of a rusting, fume-belching, oil-spewing Titanic stranded in the middle of a montane nature reserve—these images present us with a new way of thinking about seemingly familiar things. Aside from the wealth of science and the rich review of previous work to be found in Road Ecology, one of the greatest overall contributions of the book—and it is one that good science writing shares with good poetic writing—may be that it induces us, without preachiness or exhortation, to view some of the most quotidian aspects of our lives with renewed interest. “Thinking like a road ecologist” encourages us to visualize disparate, widely dispersed elements of our surroundings as interconnected, as a system. In doing so, such thinking might even encourage us to treat them differently, and better.

Literature Cited

  1. Top of page
  2. Literature Cited
  • Clark, C. 1990. The roots of rural capitalism: western Massachusetts, 17801860. Cornell University Press, Ithaca , New York .
  • Forman, R. T. T. 2000. Estimate of the area affected ecologically by the road system in the United States. Conservation Biology 14 : 3135.
  • Foster, C. H. W., editor. 1998. Stepping back to look forward: a history of the Massachusetts forest. Harvard University Press, Cambridge , Massachusetts .
  • Guariguata, M. R., and J. M. Dupuy. 1997. Forest regeneration in abandoned logging roads in lowland Costa Rica. Biotropica 29 ( 1 ): 1528.
  • Rothenberg, W. B. 1992. From market-places to a market economy: the transformation of rural Massachusetts, 1750–1850. University of Chicago Press, Chicago .
  • Young, K. R. 1994. Roads and the environmental degradation of tropical montane forests. Conservation Biology 8 : 972976.