Review
Impacts of roads and linear clearings on tropical forests

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Linear infrastructure such as roads, highways, power lines and gas lines are omnipresent features of human activity and are rapidly expanding in the tropics. Tropical species are especially vulnerable to such infrastructure because they include many ecological specialists that avoid even narrow (<30-m wide) clearings and forest edges, as well as other species that are susceptible to road kill, predation or hunting by humans near roads. In addition, roads have a major role in opening up forested tropical regions to destructive colonization and exploitation. Here, we synthesize existing research on the impacts of roads and other linear clearings on tropical rainforests, and assert that such impacts are often qualitatively and quantitatively different in tropical forests than in other ecosystems. We also highlight practical measures to reduce the negative impacts of roads and other linear infrastructure on tropical species.

Section snippets

Linear clearings in the tropics

Roads and other linear infrastructure such as power lines, gas lines, railroads and canals are among the most ubiquitous features of human activity, and are known to have important environmental impacts on natural habitats and ecosystems worldwide 1, 2. Such impacts appear to be particularly acute in tropical rainforests, for at least two reasons.

First, from a biological perspective, rainforests are characterized by a complex architecture and uniquely humid, dark, stable microclimate [3]. They

Impacts of roads and linear clearings

As summarized below, roads and other linear clearings can have an array of deleterious effects on tropical forests and their wildlife.

Reducing and mitigating the impacts of linear clearings

Various measures and design strategies can be used to curb the environmental impacts of roads and other linear infrastructure. These fall into two broad categories: local-scale efforts to reduce the impacts of new or existing linear clearings, and regional-scale efforts to limit their expansion into ecologically sensitive areas.

Vulnerability of tropical forests

As detailed above, many of the impacts of roads and linear clearings appear to differ qualitatively or quantitatively between tropical rainforests and other ecosystem types. This occurs for at least five reasons.

First, rainforests have a complex, multi-layered architecture with dense canopy cover. This creates a dark, humid, thermally stable and nearly windless microclimate in the forest understory, which contrasts with harsher, more variable conditions in linear clearings. As a result of these

Acknowledgements

We thank M. Adeney, E. Bennett, S. Blake, T. Brooks, R. Butler, M. Cochrane, M. Cohen, P. Davidar, R. Ewers, P. Fearnside, T. Lovejoy, D. Neidel, D. Nepstad, C. Peres, A. Pfaff, S. Pimm, T. Rudel, N. Sodhi, M. Steininger, J. Supriatna, J. Vincent and three anonymous referees for information, imagery and insightful comments; L. Gonzalez for help with graphics; and James Cook University, the Australian Government's Marine and Tropical Sciences Research Facility and the Smithsonian Institution for

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