documented. However, there are few integrative or large-scale studies. Sometimes the appropriate spatial scale for ecological research is not known in advance, and in that case, some ecological effects of roads may go undetected if an inappropriate scale is chosen. Few studies have addressed the complex nature of the ecological effects of roads, and the studies that have done so were often based on small sampling periods and insufficient sampling of the range of variability in ecological systems.

Recommendation: Research on the ecological effects of roads should be multiscale and designed with reference to ecological conditions and appropriate levels of organization (such as genetics, species and populations, communities, and ecological systems).

Recommendation: Additional research is needed on the long-term and large-scale ecological effects of roads (such as watersheds, ecoregions, and species’ ranges). Research should focus on increasing the understanding of cross-scale interactions.

Recommendation: More opportunities should be created to integrate research on road ecology into long-term ecological studies by using long-term ecological research sites and considering the need for new ones.

Recommendation: Ecological assessments for transportation projects should be conducted at different time scales to address impacts on key ecological system processes and structures. A broader set of robust ecological indicators should be developed to evaluate long-term and broad-scale changes in ecological conditions.

CONCLUSION: The assessment of the cumulative impacts of road construction and use is seldom adequate. Although many laws, regulations, and policies require some consideration of ecological effects of transportation activities, such as road construction, the legal structure leaves substantial gaps in the requirements. Impacts on certain resources are typically authorized through permits. Permitting programs usually consider only direct impacts of road construction and use on a protected resource, even though indirect or cumulative effects can be substantial (for example, effects on food web components). The incremental effects of many impacts over time could be significant to such resources as wetlands or wildlife.

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement