Conservation biogeography of the USMexico border: a transcontinental risk assessment of barriers to animal dispersal

The US–Mexico border bisects North America and is marked by intensive human land use and 1200 km of recently constructed barriers to human migration. These modifications may severely threaten the diverse wildlife of the region (Cohn, 2007; de la Parra & Córdova, 2007; Sayre & Knight, 2010). Anthropogenic impacts are expected to increase with future land use change and further expand fences and walls along the border (Flesch et al., 2010). The problem of anti-immigration barriers is particularly severe as US law exempts their construction from adherence to all environmental regulatory and review requirements (US Library of Congress (USLOC), 2005b). Under the REAL ID Act of 2005, the Secretary of the Department of Homeland Security (DHS) has authority to construct barriers across the entire border at any time without oversight of environmental regulatory law. To date, a binational, transcontinental analysis of the potential threats facing the border fauna, including those posed by dispersal barriers, is lacking. Section of Integrative Biology, University of Texas at Austin, 1 University Station C0900, Austin, TX 78712-0253, Ecology and Evolutionary Biology Department, Yale University, 165 Prospect Street, New Haven, CT 06520, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, MC 0116, La Jolla, CA 920930116, USA