conditions are not only affected by the construction of roads and road appurtenances (bridges and culverts) but also by the traffic on the roads and, at larger scales, by the increases in road density. The ecological effects of roads are much larger than the roads themselves, and the effects can extend far beyond ordinary planning domains. Few studies address the complex nature of the ecological effects of roads. For example, little is known about how roads impede access to foraging areas or key prey species, potentially resulting in cascading or other trophic effects. Studies assessing ecological effects are often based on small sampling periods and, therefore, do not adequately sample the range of variability in ecological systems. More research should be directed at identifying the appropriate scale at which roads affect ecological conditions.

Information on the resiliency of biodiversity components to road-related disturbances is needed to better understand the effects of roads on ecological systems. Research on the ecological effects of roads over long periods or at large spatial scales and research on the complex nature and impacts of roads within ecologically defined areas, such as watersheds, eco-regions, or species’ ranges, should be a priority. Research on the local scale should continue, however, because the context of many transportation decisions is at the local scale with direct application, and studies that address the context are likely to be the most frequently used and have the largest influence.

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