With an estimated 1.5 million deer killed annually on US roads , and potentially a greater biomass of smaller animals killed, wildlife crossings reconnect remaining land patches to facilitate healthy metapopulation function (Forman). The emerging science of Road Ecology in the U.S. has studied wildlife connectors, and claims that the combined use of fencing and wildlife connectors is the most effective structural method to guide safe passage for wildlife and reduce roadkill.
Although more relevant in less developed areas of California, wildlife crossings provide opportunities for animals to safely cross roadways that otherwise fragment habitats and isolate animal populations. In Southern California, studies show that drainage culverts are regularly used by wildlife (Sandra J. Ng). San Bernardino already has specially designed underpasses for bobcats, coyotes, and deer. An overpass is currently being planned for antelope (California Issues Solicitation for Wildlife Crossing Construction Services).
Once a road has been built, it severs an entire ecological system, disrupting hydrology and established habitats through a variety of effects, including pollution, facilitating invasive plant species movement, dividing and isolating animal populations, changing species composition, and traffic noise (Tanner, Forman). By no means do wildlife crossings mitigate the disturbance a highway has on an ecosystem but they are one step closer in realigning the potential of multifunctional freeways.
Forman, Richard T.T. Road Ecology: Science and Soultution. Washington D.C.: Island Press, 2003
Sandra J. Ng, Jim W. Dole, Raymond M. Sauvajot, Seth P.D. Riley, Thomas J. Valone. “Use of Highway Under Crossings by Wildlife in Southern California.” Study. 2001
“California Issues Solicitation for Wildlife Crossing Construction Services.” Targeted News Service, 28 March 2011
Tanner, Dawn Renee. “Road to the Future: Strategies for Wildlife Crossings and youth Empowerment to Improve Wildlife Habitat in Roaded Landscapes.” Dissertation. 2010