Beyond on-site mitigation: An integrated, multi-scale approach to environmental mitigation and stewardship for transportation projects

Federal, state, and local governments construct thousands of kilometers of roads each year in the U.S.A., as well as undertaking widening, rerouting or repair projects. Under the National Environmental Policy Act (NEPA), environmental impacts from such construction must be offset by mitigation measures (e.g., stream or wetland restoration). Unfortunately, restoration projects often are opportunistic, do not consider a broad landscape context, and have a low benefit–cost ratio. In 2007, the Maryland State Highway Administration asked The Conservation Fund, the Maryland Department of Natural Resources, and the U.S. Fish and Wildlife Service to help identify and evaluate natural resource stewardship opportunities in four Maryland watersheds that could potentially be affected by construction of a highway bypass. Stewardship activities, including conservation, restoration, or management of natural resources, would go above and beyond required mitigation. After soliciting feedback from stakeholders and reviewing pertinent literature, we modeled and validated a conservation network of high-quality wildlife and plant habitat (core areas), large contiguous natural areas (hubs), and linkages to facilitate wildlife movement and gene flow (corridors). We then ranked elements of this network at multiple scales, and identified high priority areas for conservation and restoration. Finally, we developed and tested protocols for field assessment and benefit–cost optimization. We hope that this approach can be adapted and improved by highway agencies and other entities for environmental planning and protection, and have a report available upon request with full details.