Impact of the Proposed Barrier between Mexico and the United States

On the Impact of the Proposed Barrier between Mexico and the United States 22 June 2017

WHEREAS, The American Society of Mammalogists is a non-profit, professional, scientific, and educational society consisting of nearly 3,000 members from all 50 of the United States and 60 other countries worldwide. The American Society of Mammalogists was founded in 1919 and is the world’s oldest and largest organization devoted to the study of mammals. Where appropriate and based on our scientific expertise, The American Society of Mammalogists adopts positions on issues concerning the responsible management of mammals and their habitats; and,

WHEREAS, The American Society of Mammalogists has a long history of promoting scientific management and conservation of wild mammals worldwide; and,

WHEREAS, the conservation of mammals and their habitats is intrinsically intertwined with federal policy; and,

WHEREAS, the current administration is planning to extend an existing barrier along the US-Mexico border by approximately 1,200 km, which has the potential to severely disrupt movement of mammals, and these barriers could impact at least 56 mammal species, including 4 species of international conservation concern, 23 species with limited range sizes, and 29 species with marginal distributions along the US-Mexico border (Lasky et al. 2011; Quijada-Mascarañas et al., 2012); and,

WHEREAS, approximately 134 mammalian species occur within 50 km of the border and the geographic ranges of approximately 113 species will be directly intersected by the proposed barrier (Lasky et al. 2011); and,

WHEREAS, the effects of man-made barriers have been studied on some mammalian species along the US-Mexico border and many border regions elsewhere, and have documented conclusively that barriers negatively affect the viability of some species of mammals (Epps et al. 2005; Lasky et al. 2011; Quijada-Mascarañas et al., 2012); and,  

WHEREAS, affected mammals would account for approximately 39% and 40% of US and Mexican mammalian faunas, respectively (Lasky et al. 2011; Quijada-Mascarañas et al., 2012); and,

WHEREAS, in the case of the jaguar (Panthera onca), an endangered species in the US with a draft recovery plan and critical habitat designation underway, the completion of additional barrier sections could adversely affect critical movement (e.g., gene flow) of individuals in both directions and a complete barrier would most likely result in extirpation of the jaguar in the US (Ceballos et al., 2016); and, 

WHEREAS, other protected and highly mobile carnivores such as ocelot (Leopardus pardalis), jaguarundi (Puma yagouaroundi), and Mexican gray wolves (Canis lupus baileyi) occurring along the border likely would experience similar negative impacts from the construction of additional barriers (List 2007; Marris 2006); and,

WHEREAS, areas adjacent to barriers tend to have high levels of human disturbance, removal of vegetation, and to maintain expansion of the existing barriers, such as roads and lighting (Spangle, 2007), further expands negative impacts of barriers on mammalian populations; and,

WHEREAS, boundary infrastructure has been documented to differentially affect movement of wildlife as compared to humans (MacCullum et al. 2014); and,

WHEREAS, worldwide, barriers to wildlife movement exacerbate the current extinction threats posed by human-altered landscapes and high human density and activities (Trouwborst et al. 2016); and,

WHEREAS, an informational report by the US Fish and Wildlife Service lists 111 endangered species, 108 species of migratory birds, and lands that are central to species conservation, including fish hatcheries, wildlife refuges, and protected wetlands that may be impacted by the construction of a complete barrier (USFWS IPaC Trust Resources Report, 2016); and,

WHEREAS, many scientists, including numerous ASM members, have spent their careers studying species found on both sides of the US-Mexico border; and,

WHEREAS, agreements are already in place in the form of laws and treaties (e.g., Convention on Nature Protection and Wildlife Preservation in the Western Hemisphere, 56 Stat. 1354, TS 981; and Canada/Mexico/U.S. Trilateral Committee of Wildlife and Ecosystem Conservation and Management 1995) related to migratory, trans-border, and endangered species, and the proposed extension of the existing barrier appears to violate existing international wildlife and US-Mexico border treaties; and,

WHEREAS, development of boundary infrastructure on the US-Mexico border has a high probability of affecting biodiversity, especially given the presence of rare and endangered species (Malcolm and Ya-Wei 2015), Federal policies should take into account the best available science on construction of barriers (e.g., Secure Fence Act of 2006);

THEREFORE BE IT RESOLVED, that The American Society of Mammalogists, meeting at its 97th Annual Meeting at the University of Idaho, Moscow, Idaho, 20-24 June 2017, strongly opposes border developments that impede the ability of wildlife to move freely across international borders; and,

BE IT FURTHER RESOLVED, that The American Society of Mammalogists calls upon the Federal Government to ensure that all boundary infrastructure, both existing and proposed, include features and modifications to maintain landscape permeability for mammalian populations to permit demographic and genetic exchange necessary for well-distributed, viable populations and the long-term persistence of species and mammalian community structure. The actions of the Department of Homeland Security on the US-Mexico border must receive regular environmental review to identify, monitor, and mitigate significant threats to the persistence of mammalian populations under the National Environmental Policy Act and the US Endangered Species Act.


Ceballos, G., H. Zarza, C. Chavez, and J. Gonzalez-Maya. 2016. Ecology and conservation of jaguar in Mexico: state of knowledge and future challenges. Pp. 273-288 in: Tropical conservation: Perspectives on local and global priorities (A. A. Aguirre and R. Sukumar, eds.). Oxford, University Press, U.S.A.

Lasky, J.R., W. Jetz, and T.H. Keitt, 2011. Conservation biogeography of the US–Mexico border: a transcontinental risk assessment of barriers to animal dispersal. Diversity and Distributions 17:673–687. doi:10.1111/j.1472-4642.2011.00765.x.

List, R. 2007. The impacts of the border fence on wild mammals. Pp. 77–86 in A Barrier to our Shared Environment: The Border Wall between Mexico and the United States (A. Co´rdova and C.A. de la Parra, eds.). SEMARNAT, Instituto Nacional de Ecologı´a, El Colegio de la Frontera Norte, México D.F., México.

Malcom, J.W., and L. Ya-Wei.  2015.  Data contradict common perceptions about a controversial provision of the US Endangered Species Act. Proceedings of the National Academy of Sciences 112:15844-15849.

Marris, E . 2006. Wildlife caught in crossfire of US immigration battle. Nature 442:338–339.

McCallum J.W., Rowcliffe J.M., Cuthill I.C. 2014. Conservation on international boundaries: the impact of security barriers on selected terrestrial mammals in four protected areas in Arizona, USA. PLoS ONE 9:e93679. doi:10.1371/journal.pone.0093679.

Quijada-Mascarañas, A., C.V. Ripper III, D.L. James, L. López-Hoffman, C. Sharp, R. Gimblett, M.L. Scott, L. M. Norman, R. Madellín, J.B, Callegary, R. List,  C.A.A. Wallace, P. Holm, E. Glenn, J. Leenhouts, T. Wsque, M. Culvert, R. Webb, R.J. Steidl, M.L. Villarreal, P. Nagler, W. Lacknner, M. Strum, R. Castillo-Gamez, y G. Ceballos. 2012. Desarrollo de un programa de monitoreo a nivel del ecosistema en muro fronterizo México-Estados Unidos. Pp. 157-177 en El muro fronterizo entre México y Estados Unidos. Espacios, instrumentos y actores para un diálogo constructivo (A. Córdova y C. A. de la Parra, eds.). El Colegio de la Frontera Norte, Tijuana, B.C.

Spangle, S.L. 2007. Biological opinion 22410-2007-F-0416: pedestrian fence projects at Sasabe, Nogales, and Naco-Douglas, Arizona. United States Fish and Wildlife Service, Phoenix, Arizona.

Trouwborst, A., F. Fleurke, and J. Dubrulle. 2016. Border fences and their impacts on large carnivores, large herbivores and biodiversity: an international wildlife law perspective (October 4, 2016). Review of European, Comparative and International Environmental Law 25(3). Tilburg Law School Research Paper No. 19/2016. Available at SSRN:

U.S. Fish & Wildlife Service. Trump Wall. IPaC Trust Resources Report Generated May 03, 2016 02:10 PM MDT, IPaC v3.0.2,