March 1, 2017
Bryan Bird

How splitting the land in two can have a significant impact on wildlife, landscapes, and the environment.

President Donald Trump made the border wall a central platform of his presidential campaign and within his first 7 days in office signed an executive order to build a wall along the remaining U.S.-Mexican border— all 1,254 miles of it. In addition to the effects on human communities, the wall will harm a diversity of wildlife and vast expanses of pristine wildlands and waterways, including critical wildlife movement corridors. Harm will be amplified by wall-related infrastructure and activities, including construction, improvement and maintenance of border patrol roads, camps and facilities, removal of vegetation, and traffic from patrols. Regrettably, all border wall construction can be accomplished under waivers allowed by the 2005 REAL ID Act. The act is sweeping, allowing the waiver of any federal, state, or local laws.

Border security infrastructure currently covers nearly 700 miles of the 1,954-mile United States (U.S.)-Mexico border and is lined with walls, fences and other barriers, according to the U.S. General Accounting Office. In areas closest to cities there are multiple, parallel fences and walls. In some places, there is no wall because the terrain already provides a natural barrier, such as the widest parts of the Rio Grande river or steep, rugged mountain ranges.

The impacts of this border wall on wildlife, landscapes, and the environment are substantial, including

  1. Mortality caused by construction activity, enforcement vehicles, stress and loss of habitat and access to resources.
  2. Blockage of the corridors that accommodate migrations and other movement—including northward shifts in range as species adapt to climate change.
  3. Obstruction of access to seasonally important resources.
  4. Displacement of species and disruption of wildlife ranges.
  5. Destruction, deterioration and fragmentation of habitat, including movement corridors and areas recently replanted or otherwise restored.
  6. Prevention of the gene flow necessary to keep populations healthy.
  7. Alteration of water flows and related hydrologic processes in streambeds and floodplains.

According to the United States Fish and Wildlife Service (USFWS) at least 89 endangered or threatened species, 108 species of migratory bird and four national wildlife refuges could potentially be affected by activities along the border region.

Impacted Species

The wall could end recovery of the jaguar species in the U.S. Southwest.

All jaguars identified in the U.S. during recent years are thought to have traveled north from Mexico. The wall would prevent the migration of jaguars within critical corridors between Mexico and the United States. Any wall along the border of Mexico would have to pass through jaguar critical habitat – 764,207 acres designated USFWS that contain features essential to the conservation of the jaguar and that may require special management and protection – in New Mexico and Arizona.


The endangered ocelot is another species that will be especially imperiled by border security infrastructure and an extraordinary effort to reconnect this cat’s historic habitats between the U.S. and México could be jeopardized.



Another iconic and endangered species, the Mexican gray wolf, would also suffer. The U.S. population count for 2016 is 113 and there are about three dozen south of the border. The wall would cut off these populations from each other, making recovery less likely because the isolated populations may suffer from inbreeding.


Other research has concluded that barriers disrupt movements and distribution of the low-flying, Cactus Ferruginous pygmy-owl and isolated populations of mammals such as bighorn sheep, black bears and pumas, in the Sky Islands of Arizona and New Mexico. Such isolation reduces exchange of genetic material and makes the animals more vulnerable to disease.

Impacted Landscapes

Wildlands that will be harmed include national parks, national wildlife refuges, national forests, Bureau of Land Management lands, wilderness areas, as well as state, private and Native American tribal lands. Wildlife corridors on these lands link habitat on both sides of the U.S.-Mexico border essential for species moving to find resources needed for survival.

The Sky Islands region in Southeast Arizona and Southwest New Mexico is one of the landscapes of most concern that will be impacted.

Here, forested mountaintop “islands” are separated by, and appear to float among, vast areas of grassland and desert. This unique and intricate topography and blend of tropical and temperate climates gives the landscape an impressive level of biodiversity. The Sky Islands  are among the most diverse ecosystems in the world, harboring more than half the bird species of North America, as well as black-footed ferretsbison, desert tortoise, at least 29 species of bats and several species of parrots. There are at least 41 endangered species in the Sky Islands region, including the jaguarocelot, Mexican gray wolf, thick-billed parrot and New Mexican ridge-nosed rattlesnake.

The lower Rio Grande Valley near Brownsville is another landscape that we are most concerned about as the impact to wildlife and wild lands would be substantial.

The Lower Rio Grande Valley National Wildlife Refuge complex is in this area and there are 11 unique biotic communities that have been identified. Habitat here supports 19 federally threatened and endangered species, and 57 state protected species. With over 776 plant species, 50 mammal species, 29 freshwater fish species, and 65 reptile and amphibian species this refuge complex is considered to be one of the most biologically diverse in the entire refuge system.

How will Defenders be involved?

Defenders of Wildlife’s long term strategy will employ science and reason to persuade those responsible for border security to avoid further wall or fence construction altogether or at very least avoid and mitigate any impacts on wildlife and the habitat we share with our international neighbors. This strategy will include gathering and synthesizing the most current scientific research on effects of border security infrastructure on wildlife. We will work with allies to convene an advisory committee of scientific experts to convince Homeland Security Department, Customs and Border Protection and Border Patrol to seek solutions that won’t drive wildlife to extinction.

Defenders of Wildlife is committed to protecting wildlife and habitat that could be affected by a border wall. We will join our diverse, NGO allies in the conservation, human rights, civil rights, religious and fiscal watchdog communities to demonstrate substantial opposition. Follow us on social media to stay up-to-date on the status of other developments important to wildlife conservation and our work.




Bryan Bird

Bryan Bird

Director Southwest Program
Bryan Bird directs Defenders' efforts to protect imperiled wildlife and their habitats across Arizona, New Mexico and Texas.

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