Building border walls is not a new concept but the impact they have tends to focus on the human element, of how the walls or fences will be used to keep people out, rather than the toll they take on the environment and wildlife. The first time I was introduced to how fences impact wildlife was many years ago while reading Cry of the Khalahari, which touches on Botswana’s veterinary fences that were erected to “stop the spread foot and mouth disease to cattle” and to meet strict EU regulations for the beef trade. The impact these fences had on wildlife was undeniable and brutal “many wild animals including giraffe, elephant, zebra and many species of antelope, became ensnared, cut off from migratory routes and from vital resources.” In short, many species perished as a direct or indirect result of the fences.

Botswana wasn’t the only country to erect fences for the purpose of protecting livestock, Australia put up a fence in the 1950’s to keep sheep safe from predators like dingos and wild dogs. The fence didn’t work out exactly as planned and it ended up also protecting kangaroos which turned out to be more of a problem for sheep due to the fact that they competed with them for pasture.

More recently the effects of the anti-refugee wall between Slovenia and Croatia was studied. The report showed how the barrier is hurting gray wolves, Eurasian lynx as well as possibly threatening brown bears. Suggestions to help alleviate the pressure at the fences includes: using new alternative forms of high-tech monitoring methods that would allow selected sections of a border to remain unfenced while still providing security; more carefully thought out fence alignment that would reduce it effects; and, design that minimizes the chance of wildlife entanglement and death similar to border fencing that has been “retrofitted between Kazakhstan and Uzbekistan to enable the saiga antelope to pass between the two nations.”

Habitat fragmentation caused by the fence interrupts gene flow and threatens the already small population of Eurasian Lynx – Image Wikipedia

While the report recognizes that many fences are permanent, it says the role of conservationists is critical and that our knowledge and understanding about border fences and their effect on wildlife needs to be improved. Interestingly it was found that in some cases the fences, “may unintentionally actually help conservation by preventing animals from roaming into countries with low degrees of law enforcement, by creating well-guarded spaces where human impact is minimal and by preventing the spread of wildlife diseases.”

Germany’s Cold War barriers of fences and walls that separated East and West later became an accidental nature preserve and is now part of a green belt that runs through central and eastern Europe. In China the Great Wall was found to have no major effect on wildlife as it was not one solid piece of construction but rather consisted of a series of different builds including mounds of pounded earth which later became degraded from use. However, in specific areas where the wall is truly solid a team of Chinese scientists, who conducted a study of plant species on both sides, confirmed that in these areas it was indeed a physical barrier to gene flow.

Arizona section of the U.S.-Mexico border wall – Via Northern Jaguar Project – Photo by Jay J. Johnson-Castro, Sr.

Connectivity and wildlife is a hot topic these days when it come to urban planning and building roads and freeways, but it is very unlikely that an extension of a wall at at the U.S.-Mexico border would take into account concerns for wildlife, habitat fragmentation, or gene flow for endangered species like the jaguar.  While humans can and will generally find ways around walls, wildlife from snakes and frogs to jaguars, pumas, bob cats and big horn sheep will not be able to move freely. They will be forced to adapt to smaller territories which will ultimately prove deadly to them especially when their access to food, mates and water, is cut off.

Mountain lion at border wall U.S. Border Patrol – Image Northern Jaguar Project

In 2006 the Secure Fence Act, which was responsible for the 1,000 kilometers of impenetrable barrier along the Mexico–U.S. border, had environmental laws waived for its construction. The impact of these walls on wildlife has been studied along with the effects it has had on the highly endangered ocelot. The solid metal and concrete fence further fragments ocelot habitat and kept the small population in Texas separate from the larger and more genetically diverse population in northern Mexico. Even though there were about 100 openings incorporated in the fence for wildlife they were much to small to allow larger animals like bobcats or coyotes through.

Ocelot

Wildlife biologist Mitch Sternberg told Nature that “bobcats don’t go out looking for holes in fences as they travel back and forth through brushy habitats. Overall, wildlife connectivity does not exist in these sectors anymore.” It was also noted that there were major shifts in territory due the construction for the 20 bobcats that had been collared and studied. Some simply abandoned their home range and others became trapped on one side of the wall and were eventually killed on highways while looking for new territory.

Bobcat at US-Mexico wall. Image via Triggerpit.com – Photo: ILCP photographer

In 2014 a report was released that stated the fence had little to no impact on human travel and most native species, however it had a great impact on pumas and coatis. While pumas had greater capability to roam farther in search of territory the fence meant there were less of them. With regards to coatis who are unable to move home ranges easily, researchers concluded that this could lead to a “possible collapse in their populations”. It also pointed to the fact that any impact the wall had on the behavior and populations of pumas and coatis could have serious implications for those species with whom they interact.

Coati – Image The Dodo – Jamie McCallum University of Bristol – U.S. Mexico Border

It is estimated that the border wall has the potential to impact 111 endangered species, 108 species of migratory bird, four wildlife refuges and fish hatcheries, and an unknown number of protected wetlands.

Puma – Image The Dodo – Jamie McCallum University of Bristol – U.S. Mexico Border

El Jefe, the male jaguar who caused a stir of excitement when captured on trail camera in  2016 along the Arizona side of the border, would undoubtedly be cut off from any females attempting to come from Mexico. Even though a possible new jaguar has been photographed in the U.S. it is not considered enough to help re-establish the species. Kierán Suckling, executive director of the Center for Biological Diversity told EcoWatch that “walls don’t stop people from crossing the border, but Trump’s plan would end any chance of recovery for endangered jaguars, ocelots and wolves in the border region.”

El Jefe, is believed to have crossed the U.S.-Mexico border before making his home in Arizona. (Conservation CATalyst/Center for Biological Diversity)

In December 2016 a conservation plan was released for the jaguar, a species that was systematically exterminated in its former historical habitat, by the USFWS in which they hoped to work more closely with Mexico. The plan, which is supposed to “make it easier for agencies and organizations in the U.S. and Mexico to align their efforts at restoring jaguar habitat along the border” includes keeping corridors intact so the cats can move back and forth freely. The proposed wall along the entire 2,000 mile border with Mexico would essentially be the end to the jaguars recovery in America. It would also be an ecological disaster—ripping populations and fragile ecosystems apart. Louise Misztal, biologist and executive director of conservation non-profit Sky Island Alliance in Arizona tells Motherboard that “wide-ranging mammals like mountain lions, bears, jaguars, ocelots, need to be moving between these different mountain ranges to get to food resources and water.”

Saving predators like jaguars go beyond a feel good story about bringing an endangered species back from the brink – they like other apex predators are invaluable in their ability to help regulate, naturally, other species and the ecosystem in which they reside. When apex predators disappear from the landscape trophic cascades, the top-down regulation of ecosystems by predators which is an essential aspect of ecosystem function and well-being, are disrupted.

Camera trap data from Arizona found that the wall did not prevent illegal immigrants from crossing into the United States, but wholly stopped wildlife movement. Toad looking through the metal bars of part of the existing border wall. Credit: Anonymous. Image –  Seeker by Dan Millis

A number of groups and organizations have released statements opposing the proposed wall including the National Wildlife Federation and Panthera. Jesse Lasky, an assistant professor of biology at Pennsylvania State University told Live Science that “If Trump’s wall is built, it could push endangered animals and native animals with small habitats over the edge…and If the populations on the border start disappearing, the functioning of these ecosystems could be reduced.” Bryan Bird, director of the Southwest Program for Defenders of Wildlife tells Seeker that “fences are only appropriate directly adjacent to urban areas and should not be used in wildlife corridors or other ecologically sensitive areas” and, alternative monitoring devices, which minimize the impact on wildlife, such as “virtual high-tech fencing options like unmanned aerial vehicles, motion-sensors, laser barriers and infrared cameras ” should be employed to provide security.

In addition to what the wall means for wildlife, the construction of it will have a further impact on human health and the planet as it has the potential to release about “2 million tons of carbon dioxide into the atmosphere.”

”The U.S.-Mexico border is the largest human construction that has been made to divide two countries since the great wall of china.” US-Mexico wall arial – Image via Triggerpit.com – Photo: ILCP photographer

It is widely accepted that it is a negative prognosis for wildlife and ecosystems when man-made barriers are introduced, unfortunately even with this knowledge border walls and fences are on the rise. Wildlife at the current U.S.-Mexico border wall has been documented acting confused and stressed due to their daily routines being disrupted and, without further environmental impact studies, or incorporating designs in fences that allow animals to move through, researchers will not know the extent of damage or long-term implications. Along with undoing decades of conservation efforts and work any new fences will increase the number of species at risk by further isolating them on either side, pushing wildlife like the jaguar and ocelot even more precariously close to extinction while degrading our ecosystems in the process.