Between 17 October and 29 December 2008, contractors working for the U.S. Department of Homeland Security (DHS) constructed approximately 19 km of contiguous barrier along the United States-Mexico border in the Malpai Borderlands region of southeastern Arizona. The construction was part of the U.S. Secure Fence Act of 2006, which mandated installation of fences, barriers, roads, and surveillance technology on five segments of the United States-Mexican border, totaling approximately 1120 km (or 35% of the entire border) by December 2008. To expedite implementation of the act, Congress authorized the secretary of Homeland Security to waive all or parts of 37 federal statutes pertaining to the conservation of cultural and environmental resources, including the National Environmental Policy Act, the Endangered Species Act (ESA), the Clean Air and Clean Water acts, and the Antiquities Act. Secretary Michael Chertoff exercised this authority on 1 April 2008. According to the Associated Press (28 January 2009), 962 km of barriers had been completed as of January 2009; DHS maps indicate that nearly all of the new construction is located between San Diego, California, and El Paso, Texas. The Malpai Borderlands region harbors significant cultural and ecological resources and has been the site of extraordinary conservation efforts in recent decades (Curtin 2002; Sayre 2006). Cultural sites and artifacts are ubiquitous, reflecting aboriginal human use from the Clovis period to the last days of the Apaches as well as historical Euro-American settlement. Judging from natural heritage data, there are more species of plants and animals in the borderlands than in any other place of comparable size in the United States (Brown & Kodric-Brown 1996): the Malpai planning area harbors an estimated 4000 species of plants, 104 species of mammals, 327 species of birds, 136 species of reptiles and amphibians, and the greatest known richness of bee species in the world. Thirteen species are listed as threatened or endangered under the ESA, and dozens more are protected under state laws. Since 1994 the Malpai Borderlands Group (MBG), a nonprofit organization founded by area landowners, has led a community-based, collaborative effort to protect the area from exurban development, restore fire and grasslands, and conserve livestock ranching as a viable livelihood. The MBG's achievements have been heralded and supported by philanthropists, foundations, journalists, scholars, government agencies, and environmental groups across the United States (Curtin 2002). Even as the barriers were being constructed, the MBG and the U.S. Fish and Wildlife Service signed a habitat conservation plan (HCP), granting MBG and participating landowners a permit to take individuals of 19 listed species incidental to otherwise legal ranching- and conservation-related management practices (including prescribed fires). From start to finish, the HCP took 5 years to complete; without the waiver from Congress, the new barrier would have required a comparable planning effort. The ecological value of the Malpai Borderlands is exceptionally high due to its location at the intersection of five continental biomes, but in other respects it has much in common with most of the rest of the United States-Mexico border: pronounced biogeographic variation, relatively intact natural communities of flora and fauna, and limited human development due to both natural conditions (weather, soils, rainfall, topography) and social circumstances (remoteness, low population densities, marginal economies). Indeed, it is precisely the relative lack of human impacts that has allowed the biological and cultural resources along the border to persist in situ, and it is for this reason that hardening the border may represent a threat of such great proportions. Previously, the international border had been delineated only by widely spaced monuments erected in the 1890s and a barbed-wire fence completed in the 1940s (Fig. 1). The topography is rugged and broken, defined by high mountains and drainage networks carved by floods through erodible valley soils. Few roads accessed the area, none of which were paved. The potential effects of border hardening on biodiversity are of grave concern to conservation biologists but are uncertain at this time. The Malpai Borderlands case suggests that infrastructure installed to build border barriers poses a greater ecological threat than the barriers themselves and that the top-down manner in which construction occurred undermines the social relationships on which effective conservation in the region has been built and ultimately depends. These social effects of border hardening must be assessed in addition to ecological effects. © 2009 Society for Conservation Biolog.
