Recent Road Research Reviews

Recent Road Research Reviews
Updated December 2007, this document contains citations and abstracts of the most up-to-date reviews of road research. These papers and books review the thousands of research articles on the impacts of roads.

Coffin, A.W. 2007. From Roadkill to road ecology: a review of the ecological effects of roads. Journal of Transport Geography 15: 396-406.
Transportation infrastructure affects the structure of ecosystems, the dynamics of ecosystem function, and has direct effects on ecosystem components, including their species composition. Clearly, the construction of transport lines results in the direct destruction and removal of existing ecosystems, and the reconfiguration of local landforms. However, transportation systems, and more specifically, roads, have a wide variety of primary, or direct, ecological effects as well as secondary, or indirect, ecological effects on the landscapes that they penetrate. The effects of roads can be measured in both abiotic and biotic components of terrestrial and aquatic ecosystems. The nature of road systems as network structures renders vast areas of the landscape as road-affected, with small patches of isolated habitat remaining beyond the ecological influence of roads. The increasing attention of scientists to the unintended ecological effects of roads has resulted in the emergence of the science of ‘‘Road Ecology,’’ marked with the publication of a multi-authored volume, Road Ecology: Science and Solutions, in 2003.

Switalski, T.A., J.A. Bissonette, T.H. DeLuca, C.H. Luce, and M.A. Madej. 2004. Benefits and impacts of road removal. Frontiers in Ecology and the Environment. 2(1): 21-28. http://www.fs.fed.us/rm/pubs_other/rmrs_2004_switalski_t001.pdf
Abstract: More than 885,000 kilometers of roads have been built on U.S. federal land in the past century to facilitate benefits associated with resource extraction, recreation, and transportation. These roads, however, have also resulted in many physical and ecological impacts. Road removal is being used to mitigate these impacts and restore public and private lands. Although many federal and state agencies and private landowners have created protocols for road removal and restoration priorities, research on this topic has not kept pace with the rate at which removals are being carried out. We review the hydrologic, geomorphic, and ecological benefits and impacts of three methods of road removal; identify knowledge gaps; and propose future road removal research questions. Some research has been conducted on hydrologic and geomorphic restoration following road removal; however, no studies have directly addressed restoring wildlife habitat. Road removal creates a disturbance in the short-term which may temporarily increase sediment loss; however, long-term monitoring and initial research have shown that road removal reduces chronic erosion and the risk of landslides. Future research is urgently needed to quantify how effectively road removal restores terrestrial, riparian, and aquatic habitat and other ecosystem processes.

Gucinski, H., M.J. Furniss, R.R. Ziemer, and M.H. Brookes. 2001. Forest roads: a synthesis of scientific information. General Technical Report PNW-GTR-509. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 103p. http://www.fs.fed.us/eng/road_mgt/science.pdf
This is a comprehensive review of the impacts of roads put together by the Forest Service.

Trombulak, S.C., and C.A. Frissell. 2000. Review of ecological effects of roads on terrestrial and aquatic communities. Conservation Biology 14: 18-30.
Abstract: Roads are a widespread and increasing feature of most landscapes. We reviewed the scientific literature on the ecological effects of roads and found support for the general conclusion that they are associated with negative effects on biotic integrity in both terrestrial and aquatic ecosystems. Roads of all kinds have seven general effects: mortality from road construction, mortality from collision with vehicles, modification of animal behavior, alteration of the physical environment, alteration of the chemical environment, spread of exotics, and increased use of areas by humans. Road construction kills sessile and slow-moving organisms, injures organisms adjacent to a road, and alters physical conditions beneath a road. Vehicle collisions affect the demography of many species, both vertebrates and invertebrates; mitigation measures to reduce roadkill have been only partly successful. Roads alter animal behavior by causing changes in home ranges, movement, reproductive success, escape response, and physiological state. Roads change soil density, temperature, soil water content, light levels, dust, surface waters, patterns of runoff, and sedimentation, as well as adding heavy metals (especially lead), salts, organic molecules, ozone, and nutrients to roadside environments. Roads promote the dispersal of exotic species by altering habitats, stressing native species, and providing movement corridors. Roads also promote increased hunting, fishing, passive harassment of animals, and landscape modifications. Not all species and ecosystems are equally affected by roads, but overall the presence of roads is highly correlated with changes in species composition, population sizes, and hydrologic and geomorphic processes that shape aquatic and riparian systems. More experimental research is needed to complement post-hoc correlative studies. Our review underscores the importance to conservation of avoiding construction of new roads in roadless or sparsely roaded areas and of removal or restoration of existing roads to benefit both terrestrial and aquatic biota.

Wisdom, M.J., R.S. Holthausen, B.C. Wales, C.D. Hargis, V.A. Saab, D.C. Lee, W.J. Hann, T.D. Rich, M.M. Rowland, W.J. Murphy, and M.R. Eames. 2000. Source habitats for terrestrial vertebrates of focus in the interior Columbia basin: broad-scale trends and management implications. Volume 1 – Overview. Gen. Tech. Rep. PNW-GTR-485. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station.
http://www.fs.fed.us/pnw/pubs/gtr485/gtr485v1.pdf
Starting on page 112, this document reviews the impacts of roads on terrestrial vertebrates.

Forman, R.T.T., and L. Alexander. 1998. Roads and their major ecological effects. Annual Review of Ecology and Systematics 29: 207-231.
Abstract: A huge road network with vehicles ramifies across the land, representing a surprising frontier of ecology. Species-rich roadsides are conduits for few species. Roadkills are a premier mortality source, yet except for local spots, rates rarely limit population size. Road avoidance, especially due to traffic noise, has a greater ecological impact. The still-more-important barrier effect subdivides populations, with demographic and probably genetic consequences. Road networks crossing landscapes cause local hydrologic and erosion effects, whereas stream networks and distant valleys receive major peak-flow and sediment impacts. Chemical effects mainly occur near roads. Road networks interrupt horizontal ecological flows, alter landscape spatial pattern, and therefore inhibit important interior species. Thus, road density and network structure are informative landscape ecology assays. Australia has huge road-reserve networks of native vegetation, whereas the Dutch have tunnels and overpasses perforating road barriers to enhance ecological flows. Based on road-effect zones, an estimated 15-20% of the United States is ecologically impacted by roads.

Books:
National Research Council. 2005. Assessing and Managing the Ecological Impacts of Paved Roads. Washington D.C.: The National Academy Press.
From Preface: “This report attempts to consolidate understanding in a number of areas – how roads interact with different ecological structures and processes across scales of space and time; how the legal framework for evaluating ecological effects intersects with the scales of ecological features; and how ecological considerations can be integrated better into all phases of road development-from planning to use.
The compilation of current understanding of the effects of roads on ecological processes and structures is a major focus of this report. We found that most of the current knowledge is about aspects of the environment that change over short time periods and small areas and that ecological processes and structures that cover large areas over broad time scales have been largely overlooked.”

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, T.C. Winter. 2003. Road Ecology – Science and Solutions. Washington D.C.: Island Press.
The book explores the history of the five million mile road network in North America and the impacts of that road system on wildlife, aquatics and hydrology, vegetation and natural landscapes. Using an interdisciplinary approach, the book brings together concepts from wildlife biology, water chemistry and population ecology to develop a cohesive model from which to base sound transportation policy. Road Ecology provides in-depth exploration of wildlife mitigation structures and also includes some discussion of road removal. Perhaps more importantly, it defines a new field of science on ecological road research.

Havlick, D.G. 2002. No Place Distant – Roads and Motorized Recreation on America’s Public Lands. Washington, D.C.: Island Press.
This book is a comprehensive review of the cumulative ecological effects of more than half million miles roads and the millions of off-road vehicles on Federal lands. He starts with the history behind road building on public lands and how off-road vehicles gained popularity. The author then proposes solutions such as road removal using case studies from Redwood National Park and the Clearwater National Forest.

Sherwood, B., D. Cutler, and J. Burton. 2002. Wildlife and Roads – The Ecological Impact. London: Imperial College Press.
This book summarizes papers presented at a meeting of the Linnean Society of London in 1998. “Among the topics discussed there are papers on legal aspects, transportation interests, planners’ and contractors’ viewpoints, plant and animal ecology and innovative solutions to some of the problems that roads inevitably impose on the natural environment.”

Wildlands CPR Road and ORV Database
http://www.wildlandscpr.org/bibliographic-database-search
Wildlands CPR continues to maintain and update a bibliographic database of over 12,000 citations documenting the physical and ecological effects of roads and off-road vehicles. In the U.S. alone, there are 6 million kilometers of public roads and over 36 million registered off-road vehicles. This database was created to help people access relevant scientific literature on erosion, fragmentation, sedimentation, pollution, effects on wildlife, aquatic and hydrologic effects, and various other up-to-date information on the impacts of roads and off-road vehicles. The database contains citations for both scientific and "grey" literature including journal articles, conference proceedings, books, lawsuits, and agency reports most with accompanying abstracts.