• Mexican conservationists are alarmed over Trump’s wall, with the loss of connectivity threatening already stressed bison, pronghorn, bighorn sheep, bears and other animals.
  • About one-third of the border, roughly 700 miles, already has fencing; President Trump has been pushing a controversial plan to fence the remainder.
  • A wall running the entire nearly 2,000-mile frontier from the Pacific Ocean to the Gulf of Mexico, conservationists warn, would be catastrophic for borderland ecosystems and many wildlife species, undoing years of environmental cooperation between the two countries to protect animals that must move freely or die.
  • The wall is currently a key bargaining chip, and a sticking point, in ongoing immigration legislation negotiations taking place this week in Congress. Also expected this week: a federal court ruling on whether the administration can legally waive environmental laws to expedite border wall construction.
Bison in the Janos Valley of Chihuahua, Mexico, where protected grasslands in the U.S. and Mexico create a bi-national wildlife corridor. The continuity of this habitat is threatened by President Trump’s border hardening plans. Photo by Rurik Hernán List Sánchez.
Bison in the Janos Valley of Chihuahua, Mexico, where protected grasslands in the U.S. and Mexico create a bi-national wildlife corridor. The continuity of this habitat is threatened by President Trump’s border hardening plans. Photo by Rurik List.

Rurik List began studying wildlife south of the U.S.-Mexico border in 1994, doing research in the expansive grasslands of the Janos Valley in the Mexican state of Chihuahua. Back then, the international boundary was pretty porous there, marked only by barbed wire fencing. Most animals could easily pass over, under, or if they were bison, bust right through it, in their quest for food, water, mates, or suitable habitat as they moved between Chihuahua and New Mexico.

In late 2008, things changed.

Flying over the Janos Valley a few months later, List, a Mexican ecologist now at Universidad Autónoma Metropolitana-Lerma, saw that the U.S. government had erected stout, neck-high  crisscrossed steel struts called Normandy barrier across about half of the six-mile (10-kilometer) wide valley, bisecting the grasslands.

From that point forward, Mexico’s only bison herd (Bison bison), numbering around 100 animals, could no longer just muscle their way into the country in search of greener pastures wherever they liked. They’d have to walk the long way around the new barrier, or just stay put. So would pronghorn (Antilocapra Americana). And bighorn sheep (Ovis canadensis). List believes both species rely on the bison holes, allowing their small U.S. populations to intermix with even smaller Mexican ones — herds with a tenuous foothold after near annihilation by hunters.

Still, most of the valley’s smaller wildlife — foxes, rodents, lizards, birds, and more — weren’t impeded by the new Normandy barrier. However, on the same flight List found a far greater obstruction dividing north from south at another of his border zone study sites near the town of Agua Prieta, where fencing twelve or more feet high (3.5 meters) now ran the line. “That type of barrier, it cannot be crossed by most animals and also some birds,” List told Mongabay.

Now looms a far bigger threat: President Trump’s promised “big, beautiful wall” aimed at stopping undocumented human migration and drug trafficking along the entire U.S.-Mexico border. That much-debated structure is currently a key bargaining chip, and sticking point, in immigration negotiations taking place this week between Republicans and Democrats in the U.S. Congress. By many accounts, the negotiations are wide open, but the pressure is on to reach an agreement by March 5. That’s when Trump is terminating the Deferred Action for Childhood Arrivals program (DACA), which has been protecting unauthorized immigrants brought to the U.S. as children from deportation. But the president has said he is willing to reinstate the program if he receives $25 billion for his wall in exchange, to be spent over ten years.

As recently as February 5 Trump tweeted: “Any deal on DACA that does not include STRONG border security and the desperately needed WALL is a total waste of time. March 5th is rapidly approaching and the Dems seem not to care about DACA. Make a deal!”

List and other Mexican scientists and conservationists are very concerned about whether or not the U.S. will decide to build its mega-wall. Small picture: a nearly impermeable border wall in the Janos Valley will stop most wildlife in their tracks and gravely threaten Mexican populations of bison, pronghorn, and bighorn sheep. Big picture: a wall running the entire nearly 2,000-mile frontier from the Pacific Ocean to the Gulf of Mexico, List and other conservationists warn, would be catastrophic for borderland ecosystems and many wildlife species, undoing years of environmental cooperation between the two countries to protect animals that must move freely or die.

If Trump’s wall is built, “this barrier will rewrite the biological history of North America. A history that for millennia allowed animals to travel along the grasslands and forests from Mexico to Canada,” List wrote in an issue of Jornada Ecologica. “The future of the bison and many other species that the two countries share is at stake at the border.”

Mexican Biologist Jesus Pacheco stands near a section of Normandy barrier running alongside old barbed wire fencing near the Antelope Wells border crossing between New Mexico, U.S., and Chichuahua, Mexico. Photo by Rurik List.

Wall-to-wall problems with Trump’s wall

Notably, Trump didn’t originate this north-south wildlife connectivity conundrum, though his plan promises to greatly magnify it. About one-third of the border already has one of three kinds of fencing [pdf]. There are 300 miles of low vehicle barriers (such as the already mentioned Normandy barriers), which are relatively permeable for most species. The remaining 405 miles consists of formidable walls, typically 15 feet or more high (4.5 meters), called pedestrian fencing. In some places these walls are doubled or even tripled, destroying connectivity.

The George W. Bush administration waived numerous environmental laws to erect most of this infrastructure in the mid-2000s, to conservationists’ deep and abiding dismay. Activists have since vocally opposed wall building on environmental, humanitarian, budgetary and practical grounds, and analysts have questioned whether a full wall, as Trump envisions it, could ever be built; some Bush-era attempts to seize private land for wall construction are still tied up in court. There are even signs Trump may be willing to settle for something less than the coast-to-coast structure he’s been hawking.

Nevertheless, the Trump administration has largely remained adamant, and pushed ahead with total disregard for environmental considerations. It commissioned eight 30-foot tall wall prototypes near San Diego that would certainly block most Earth-bound wildlife. The administration also has already waived dozens of environmental laws in several places in order to proceed. It has declared its intent to waive U.S. Endangered Species Act protections for jaguar to build walls across habitat specially designated for the species. And the administration announced plans to start its wall-building by erecting fence right through the heart of the Santa Ana National Wildlife Refuge in Texas, provoking a large protest.

Asked whether U.S. Customs and Border Protection (CBP), the agency in charge of border infrastructure, would conduct any environmental review for its wall projects, Carlos Diaz, the agency’s southwest branch chief, told Mongabay that it would follow procedures similar to what it did during the Bush era. In an email, Diaz conveyed the following statement from CBP officials:

“CBP is committed to responsible environmental stewardship in the implementation of its border security infrastructure projects. CBP will utilize existing data where present as well as conduct natural and cultural resources surveys of project areas where no data currently exists. In addition, CBP will prepare environmental planning documents that evaluate the environmental impacts from the execution of the project…. Environmental planning of border security infrastructure projects will analyze whether the construction footprint will have indirect or direct effects on threatened or endangered species or their habitats. In addition, CBP incorporates design elements that take into consideration water ways such as rivers or ephemeral washes”.

Diaz pointed to two examples of places where the agency installed features in a total of 71 miles of border fencing to allow wildlife to pass. However, many conservationists don’t think much of how CBP handles environmental reviews when it is not bound by environmental laws. Dan Millis, borderlands program coordinator with the Sierra Club’s Grand Canyon chapter in Tucson, Arizona, wrote in an email:

“Under the waiver, CBP’s environmental planning documents are window dressing, to put it nicely. They hire a contractor to write non-descript paragraphs about species of concern in a project area, but many key species are often omitted. The alternatives considered are sorely lacking, meaning that CBP only provides two alternatives: the proposed action or no action. This makes it very clear that they are only trying to check off the boxes but are not complying with protection laws or consulting with impacted communities in a meaningful way.”

The Sierra Club has petitioned the CBP over its “woefully inadequate planning documents” for years, Millis said. This fall the group filed suit against the U.S. Department of Homeland Security over its granting of legal waivers in building wall segments and prototypes in California.

Trump border wall prototypes being built in October, 2017, near the Otay Mesa Port of Entry in San Diego, California. Photo by Mani Albrecht/U.S. Customs and Border Protection via Flickr.

Borderland wildlife at risk

Studying wildlife in the borderlands isn’t easy. Ecologists face personal safety concerns from smugglers and vandalism of their gear, while some researchers say that on the U.S. side of the border CBP officers discourage their presence and the placement of camera traps. Consequently scientists weren’t able to gather much baseline data on animal populations before border walls first went up, so it’s hard to know how the walls have changed things. Even so, there is a virtual consensus among scientists that existing walls are terrible for connectivity.

“It is particularly challenging to monitor exactly how bad it is right now for animals, but our understanding of how wildlife needs to move from one place to another, migrate, disperse, adapt to changes in the landscape, it all points towards the need to keep spaces open. And so the current border wall is definitely a piece of infrastructure that fragments the landscape,” said Juan Carlos Bravo, Mexico program director for the U.S.-based Wildlands Network, an NGO.

Last March, Bravo authored a report [pdf] identifying numerous areas along the Sonoran and Chihuahuan border with the U.S. where improving habitat connectivity is key for flagship species like bison, pronghorn and jaguar (Panthera onca), all of which are listed as in danger of extinction in Mexico. Recent jaguar sightings in southern Arizona caused a stir among scientists and the public. The species, once common throughout the U.S. southwest, was hunted to oblivion there by the 1960s. The big cats had made their way north from Mexico through remaining gaps in border fencing, sparking hopes that the species might one day recover in the United States.

“We know that there’s been three jaguars recently in the U.S. We have no way of knowing if right now there should have been six or seven or ten,” but were prevented from entering the country by border barriers, Bravo said.

A camera trap image of a jaguar in Arizona, where three of the big cats have been documented in recent years. They are thought to have made their way into the U.S from Mexico. Photo courtesy of U.S. Fish and Wildlife Service.
A camera trap image of a jaguar in Arizona, where three of the big cats have been documented in recent years. They are thought to have come into the U.S. from Mexico. Photo courtesy of U.S. Fish and Wildlife Service.

The animal species most likely to be negatively affected by a hardened border are those that have tiny populations in one country that must stay in contact with larger populations in the other in order to remain viable and genetically resilient. Examples include jaguar in the U.S. and ocelot (Leopardus pardalis), bison, pronghorn, and bighorn sheep in Mexico.

Bravo also pointed to black bears (Ursus americanus) in and around Sonora’s Ajos Bavispe reserve, about 25 miles (40 kilometers) south of the border. Mexico lists the species as in danger of extinction, and a small group of bears there regularly crosses into Arizona, where the species is much more abundant. “These bears face the potential of ending up genetically isolated and more susceptible to drastic changes in the landscape.” Bravo said. Such landscape alterations are likely on the way as climate change escalates.

In addition to being a barrier to migration, border walls create other problems for wildlife. Animals tend to walk along the roads that usually parallel the walls, where they can become roadkill or easy targets for poachers, List pointed out. Human activity and floodlights can disturb their foraging. Walls also impact the ecosystem itself, altering water flows during rainstorms, causing severe erosion, and affecting critical riparian habitats. As climate change continues to intensify storm events, that will likely become a bigger problem.

It’s not just large, furry creatures that will be affected by Trump’s wall. No less than 841 vertebrate species, many of them birds, reptiles, and amphibians, and about 180 of them already in danger of extinction, would be negatively affected by a border wall spanning the entire frontier, according to unpublished research led by scientists at the National Autonomous University of Mexico — and that doesn’t include fish, invertebrates, or plants. A factsheet produced by Mexico’s National Institute of Ecology and Climate Change cites similar figures: 800 species would be affected, 111 of them already in danger of extinction.

Fencing also compounds problems for wildlife already threatened by poaching and habitat fragmentation due to mining, roads, and other human activities, conservationists say. Add global warming to that mix, and all bets are off. As temperatures have risen, borderland species have already begun moving northward to find livable habitat, but Mexican species could find their escape routes blocked by Trump’s wall.

“This is the moment when we would need to have an open border, not the time to close it,” List said.

Kit foxes in the Janos Valley of Chihuahua, Mexico. The species is considered threatened in Mexico, and would likely be harmed if the U.S. hardens the border. Photo by Rurik List courtesy of CONABIO.

Trump wall fatigue in Mexico

Mexican conservationists and scientists have aired their concerns about the proposed wall in papers, book chapters, reports, and presentations. But whereas their U.S. counterparts have formed coalitions, filed lawsuits, staged protests, and petitioned their government against the mega-infrastructure project, there seems to be little organized opposition in Mexico.

“I believe that people feel discouraged and left out of the equation,” Bravo said, adding that Mexicans are grappling with other serious environmental and human rights issues, while an upcoming June presidential election is capturing the media’s attention.

Gerardo Carreón-Arroyo, the Hermosillo, Sonora-based conservation director of the Mexican NGO Naturalia, said no one organization has assumed leadership on the issue and dedicated staff, time, and money to coordinating an organized response among Mexican groups and institutions opposed to the wall. Instead, groups like Naturalia are trying to form alliances with U.S. groups, he said, adding “together we can have more voice, more power and constancy in the fight to keep biological corridors open.”

Border wall divides Sonoyta, Sonora, Mexico from Organ Pipe Cactus National Monument in Arizona, U.S. Photo by Rurik Hernán List Sánchez.
Border wall divides Sonoyta, Sonora, Mexico from Organ Pipe Cactus National Monument in Arizona, U.S. Photo by Rurik List.

As for Mexico, while officials have expressed opposition to the mega-barrier that could disrupt the country’s northern ecosystems and water supplies, it’s not clear how much diplomatic muscle the country is flexing to try to block it. In September, Diaz shared the following statement from CBP officials: “At this point CBP has not received input from the Mexican government on new border infrastructure.” Asked for an update at press time, CBP officials responded indirectly, stating “CBP has always regarded environmental stewardship as one of its top concerns and regularly solicits input from stakeholders on potential solutions to minimize impacts to resources.”

Spokespeople from Mexico’s National Commission of Natural Protected Areas and National Institute of Ecology and Climate Change either declined requests for interviews, did not respond to emailed questions, or did not follow through on promises to arrange interviews or respond to questions. One institute employee said that staff had been told not to speak to the press on the topic, even though the institute and its parent agency, the Ministry of Environment and Natural Resources, have a history of supporting borderlands conservation and have published materials critical of the U.S.’s border wall efforts. Employees of Mexico’s Secretariat of Foreign Affairs did not respond to emailed questions and a request for an interview.

The Mexican government’s acquiescence has disappointed conservationists. “The president, Peña Nieto, is saying we won’t pay for the wall. That’s the extent of the wall argument, officially. And for me that’s very poor,” List said. “The issue should not be who will pay for it. The issue should be this shouldn’t be built.”

A bighorn sheep in Sonora, Mexico. Individuals cross the border between the U.S. and Mexico, where they are subject to poaching. Photo by Iván Montes de Oca Cacheux courtesy of CONABIO.

Something there is that doesn’t love a wall

Rancho Los Fresnos is a 4,000-hectare (9,884 acre) wildlife reserve abutting the U.S.-Mexico border in Sonora. The conserved area includes a portion of the Sky Islands archipelago — rolling grasslands, woodlands, with an extensive number of desert springs, making it an important source of water for the region. The reserve harbors more than 280 migratory bird species, 68 reptile and amphibian species, and 87 mammal species. Puma (Puma concolor), lynx (Lynx rufus), and beaver (Castor canadensis), which Mexico lists as in danger of extinction, all call the reserve home. Los Fresnos also shelters several amphibian species that are dwindling north of the border, according to Carreón-Arroyo of Naturalia, which acquired the property in 2006.

Today, a permeable Normandy barrier marks the six-mile (nearly 10-kilometer) international border at Los Fresnos, and Carreón’s chief desire is to keep it that way. He dreads the extension of the 18-foot-tall impermeable border walls stretching out into the wild from the nearby towns of Nogales, Agua Prieta, and Naco.

These walls not only block wildlife, said Carreón, but also disrupt water flow. Border walls were blamed for devastating floods in Lukeville, Arizona, and Sonoyta and Nogales, Sonora, in 2008. “Right now this [nearby] barrier is still permeable, and it’s still friendly for wildlife and the conservation of the area,” he added, “But … the wall is surrounding this important little region of the San Pedro River Basin.”

A hardened border closing off Los Fresnos would irreparably harm the area’s wild and human residents, likely damaging a water source vital to nearby cities and agricultural interests, Carreón-Arroyo said. He argued that the existing barrier is sufficient for blocking vehicles, and that the U.S. government has already invested heavily in surveillance technology and personnel, making a more formidable wall unnecessary in the area.

“The problems and risks that this wall building could bring won’t only affect those of us who live [here]” he said, “but the whole society via the environmental services that this big region, the Sky Islands, provides to both sides of the border.”

Then there are the aesthetics. Responding to the sight of a wall interrupting natural landscapes, Carreón-Arroyo declared: “It’s a shock. It’s an emotional, environmental shock, and a form of repression.”

Border wall near Naco, Arizona, not far from the Rancho Los Fresnos wildlife reserve in Sonora, Mexico. Photo by Gerardo Carreón-Arroyo.
Border wall near Naco, Arizona, not far from the Rancho Los Fresnos wildlife reserve in Sonora, Mexico. Photo by Gerardo Carreón-Arroyo.

If Trump succeeds in building his great wall, a particularly objectionable outcome for List would be the waste: of resources, of work, of money, and the squandering of the long history of cooperation on conservation between two friendly nations. The U.S. and Mexico have worked deliberately to establish interconnected protected areas on both sides of the border, to maintain cross-border landscape corridors, and to reintroduce species like the Mexican wolf (Canis lupus baileyi), which had been hunted to the brink of extinction, among other joint conservation activities.

All this requires a porous border to succeed.

“A lot of money, effort, information has been [invested], over decades, to maintain this biodiversity,” List said. “And from one day to the other bulldozers have stopped the continuity of these ecosystems [by setting] up walls and other types of fences.”

Two potentially game-changing events are currently on the agenda. There’s that immigration debate and decision in the U.S. Congress, with a looming DACA deadline of March 5. Also, last Friday there was a hearing at the U.S. District Court in San Diego for three consolidated lawsuits, including the one by the Sierra Club, that question the Department of Homeland Security’s waiving of laws to expedite border wall construction. The federal judge who will hear the case? It’s none other than Gonzalo Curiel, whom Trump attacked in 2016, saying his Mexican heritage made him unfit to impartially handle a class-action lawsuit against Trump University. A ruling is expected later this week.

For now, the fate of the wall, of wildlife connectivity and borderland ecosystems, rests in the hands of the U.S. Congress — and Judge Curiel.

Ferruginous pygmy owls (Glaucidium brasilianum), a low-flying species whose dispersal is stymied by high border fencing. Photo by greglasley via iNaturalist (CC BY-NC 4.0).

Banner image: Bison in the Janos Valley of Chihuahua, Mexico. A population of about 100 bison lives in Mexico, where they are listed as a species in danger of extinction. The herd’s trips from the U.S. to Mexico have been curtailed by a hardening of the border in the Janos Valley. Photo by Rurik List courtesy of CONABIO.

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