Conservation and connectivity across the border wall

Border wall CaliforniaThe fence that runs along sections of the 3,200 km U.S.-Mexico border undoubtedly has a large impact on humans and issues of immigration.  Debate on whether it should be expanded consistently dominates news cycles.  However, its potential impact on wildlife is also significant.  Aside from political considerations, questions abound over how this type of barrier will impact habitat connectivity in the region.  Numerous species of conservation concern live along the borderlands, including key predators such as jaguars and ocelots.

A recent article in BioScience, supported by over 2500 scientist signatories, calls for action to address three key conservation issues with the border wall and how it impacts biodiversity.  First, it bypasses critical environmental laws such as the Endangered Species Act and the National Environmental Policy Act.  Second, it undermines the value of research and protected lands in the region, which constitute 18% of the borderlands.  Third, it highly disrupts landscape connectivity by providing a physical barrier to dispersal that fragments and isolates populations inhabiting both sides of the border.

Included with these issues is an analysis of species that live in the borderlands.   Results show that the border bisects the geographic ranges of over 1500 native terrestrial and freshwater animal and plant species.  This includes 62 species listed as Critically Endangered, Endangered, or Vulnerable by the International Union for Conservation of Nature (IUCN) Red List.

In addition, more than one-third of U.S. nonflying native terrestrial and freshwater animal species would be cut off by a continuous wall from the 50% or more of their range that is south of the border.  This can lead to isolated pockets of individuals, and divided species ranges that contain only a small percentage of the overall population. The asymmetry between populations on either side of the border can be problematic, as management actions may focus on core populations when peripheral populations are most in need of conservation action.

US-Mexico borderlands Defenders of Wildlife

In general, we don’t know enough about the influences of fences on wildlife and ecosystems.  Connectivity is guaranteed to be altered by continued border wall construction, although exactly how and for which species is uncertain.  Efforts to protect wildlife corridors that cross the borderlands are already underway, and would benefit from greater support.  The problems species in the region face from disrupted connectivity at the border wall will only be exacerbated as climate change forces individuals to shift ranges.  There is a great need for ecological consequences to be as important as political ones.


Peters R, Ripple WJ, Wolf C, Moskwik M, Carreón-Arroyo G, Ceballos G, Córdova A, Dirzo R, Ehrlich PR, Flesch AD, List R, Lovejoy TE,Noss RF, Pacheco J, Sarukhán JK, Soulé ME, Wilson EO, and Miller JRB. 2018. Nature divided, scientists united: US–Mexico border wall threatens biodiversity and binational conservation. BioScience 68(10):740-3.

Thornton DH, Wirsing AJ, Lopez‐Gonzalez C, Squires JR, Fisher S, Larsen KW, Peatt A, Scrafford MA, Moen RA, Scully AE, King TW, and Murray DL. 2018. Asymmetric cross‐border protection of peripheral transboundary species. Conservation Letters 11(3): e12430.

Jakes AF, Jones PF, Paige LC, Seidler RG, and Huijser MP. 2018. A fence runs through it: A call for greater attention to the influence of fences on wildlife and ecosystems. Biological Conservation 227:310-8.

Borderlands Restoration Network

2018-12-03T11:27:06-04:00 November 26th, 2018|

About the Author:

Heather Cayton
Heather Cayton is the Managing Director of and a Research Assistant at Michigan State University. She received her B.S. from the University of Virginia and her M.S. from Virginia Tech, and has spent the past ten years studying corridors and rare butterflies in North Carolina.