Highways can impact and degrade natural systems and wildlife populations in a variety of ways including: alteration of streams and drainage systems; reduction of wildlife dispersal necessary for feeding, breeding, and colonization of new habitat; increase in noise and artificial light pollution; direct habitat loss and indirect loss due to future development that the roadway may encourage; reduction of water quality from runoff; and an increase of wildlife road-kill mortality. Roadways also create an edge-effect or vegetated area that may facilitate the dispersal and proliferation of exotic plants and animals.
Highways can also contribute to the fragmentation and isolation of regional habitat systems, resulting in chronic road-kill mortality for many wildlife species, including rare or state or federally listed species. They may also represent important predator or prey species, which are characteristic of native upland and wetland habitat types managed by state and federal agencies on lands adjacent to road rights-of-way. Noteworthy among these species are wide-ranging mammals such as the Florida black bear and the endangered Florida panther, which have been historically impacted by roads on a regional and statewide basis. Other species that may be adversely affected by roadways include but are not limited to: fox squirrels, eastern indigo snake, wading birds, turtles, invertebrates, and fish. FWC considers wildlife crossings an important design component, along with other avoidance, minimization and mitigation measures, when evaluating roads and highways for potential impacts to fish and wildlife resources.
The 1000 Friends of Florida has an extensive chapter in their “Wildlife habitat planning strategies, design features and BMPs for Florida communities and landowners” that discusses many important factors to be considered in transportation planning.
Defenders of Wildlife also provides access to Highways and Habitats Publications that provide guidance to designing transportation corridors effectively to minimize habitat fragmentation and facilitate safe, cost-effective measures for wildlife passage.