The House of Representatives yesterday approved a spending bill that includes $1.6 billion to start building the “contiguous and impassable wall” along the U.S. border with Mexico that President Donald Trump made a centerpiece promise of his campaign for the White House. The wall funding is expected to encounter stiff resistance from Democrats in the Senate, who have vowed to block the project. But the House’s move is worrying some researchers who are closely following the funding battle: conservation biologists who are concerned a wall could further complicate efforts to save species that routinely move between the two nations.
“[As conservation researchers,] we see beyond borders. The way we see conservation does not stop at a political border just because our interests stop there," says Sergio Avila, a conservation scientist at the Arizona-Sonora Desert Museum in Tucson.
One of those species is the jaguar (Panthera onca), a species sometimes described as a “reluctant warrior” for its powerful jaws but shyness around humans. The jaguar once ranged as far north as the Grand Canyon in Arizona and as far south as Argentina. These days, however, jaguars occupy 60% of that historic range, and are mostly absent from the United States, where the cat is classified as endangered under the U.S. Endangered Species Act (ESA). Efforts to restore U.S. populations had been mired in a multidecade struggle to develop a workable strategy. But last year that effort reached a landmark of sorts: the release of a 508-page draft recovery plan developed by a multinational team of experts. It lays out a 50-year roadmap for rebuilding jaguar populations that could cost some $600 million to fully implement.
Even under the most optimistic scenarios, the plan faces formidable obstacles. It is still at least a year away from being finalized, and it is not a legally binding document—so it will be up to Congress and the Secretary of the Interior to request and provide the needed funding.
Now, Trump’s proposed wall is presenting another challenge to the jaguar’s future. Biologists say the barrier could block paths the cats have historically used to move across the border, and could be key to allowing it to recolonize in the United States.
Jaguar enthusiasts note that, ironically, the battle over the wall comes just as U.S. researchers have had one of their best years for jaguar sightings in a long time. Three different animals were spotted in the United States in 2016, including one cat never seen before. It was photographed in the Dos Cabezas Mountains, 96 kilometers north of the U.S.–Mexico border. That’s the farthest north of Mexico a jaguar has been seen in decades, the Arizona Republic reported. “That’s a pretty big deal,” says Howard Quigley, executive director of the jaguar program at Panthera, a group based in New York City with researchers spread across the continent, who co-led the science team that helped write the jaguar recovery plan.
There is still no clear plan for what Trump’s wall might look like, or exactly where along the border it would be built. More than 1050 kilometers of fencing already exist along the 3201-kilometer frontier between the two nations, according to the Department of Homeland Security (DHS). And earlier this year, designers submitted more than 200 possible configurations for filling the gaps, including plans for solid concrete barriers dozens of meters high as well as more permeable structures, in response to a DHS request. (Trump has suggested it could be a clear barrier adorned with solar panels, which would produce electricity that could be sold to help pay for the wall’s construction.)
Normally, such a massive federal construction project would have to go through environmental reviews that can take years. The U.S. Fish and Wildlife Service, for example, would have to weigh in on how the wall might affect any species listed under the ESA, such as the jaguar. But earlier this year, Interior Secretary Ryan Zinke suggested the White House might invoke a provision of a 2005 immigration law that could allow federal officials to sidestep those reviews. Such moves would likely draw lawsuits from environmental groups and others.
Recovering the “reluctant warrior”
All of the jaguars seen in the United States—about one every 3 years—are believed to have originated from a population located about 210 kilometers south of the border. That’s why one major focus of the draft recovery plan is maintaining “connectivity” between the two nations, by protecting cross-border corridors that connect Arizona, New Mexico, and the Mexican states of Sonora and Chihuahua. In particular, biologists want to enable Mexican jaguars to use some of the 309,263 hectares of land in the Southwestern United States that biologists have identified as “critical habitat.”
Maintaining such an expansive range is especially crucial for the jaguar, biologists say, because unlike other large carnivores that occur over large landscapes, jaguars do not have genetically distinct subpopulations. That means “whether you take the DNA of a jaguar from northern Argentina or from northern Mexico, they are essentially genetically the same,” Quigley says. The best way to maintain a diverse, healthy population is to allow cats from various regions to intermingle, enabling genes to flow throughout the population.
Biologists warn that when species lose large swaths of habitat and get cut off from other populations, they face the devastating health effects associated with inbreeding. Compared to their South American relatives, jaguars living in Mexico have the lowest genetic diversity of the species, Quigley and colleagues concluded in a 2016 study appearing in PLOS ONE.
“Eventually, they're so unhealthy that they can't survive and they're their own worst enemy,” says Melanie Culver, a conservation geneticist at the University of Arizona in Tucson who worked on the recovery plan.
Fences and walls complicate that intermingling, notes the recovery plan, which received “well over 200 emailed comments and a handful of written letters” during a public comment period, according to the Arizona Daily Star. And biologists fear a border wall—if ever funded by Congress and built—could entirely block the cat from the northern United States end of its historic range.
But any wall is unlikely to prevent humans from moving across the border, say wall critics. To underline that point, some cite a quote from Janet Napolitano, a former governor of Arizona and Secretary of Homeland Security under President Barack Obama: “Show me a 50-foot wall and I'll show you a 51-foot ladder,” Napolitano said in 2005.
“Humans will always be able to get across—they'll find a way,” Culver says. “But the wildlife eventually will lose their ability. They can't go out and buy a ladder.”
The Congressional battle over funding the wall is likely to continue for months, or even years.
Rachael Lallensack is an intern with Nature in Washington, D.C. She reported and wrote this story while an intern at Science.