The biggest single threat to reestablishing a US jaguar population is Trump’s border wall, wildlife advocates say. In recent years, two, or possibly three lonely males have been documented in the desert mountains southeast of Tucson, Arizona. The multi-billion dollar border wall envisioned by President Trump would cut them off from the females in a population of 125 to 150 jaguars, some 80 miles south in the northern Sonora region of Mexico.

“A viable jaguar population could be reestablished in the US, but not if the wall is built,” said Howard Quigley, a jaguar expert at Panthera, the global wild cat conservation nonprofit.

Jaguars (Panthera onca), the largest cat in the Western Hemisphere, are commonly thought to be beasts of the jungle. A century ago, they were found in the deserts and mountains from southern California to Louisiana, and as far north as the Grand Canyon. The US government paid bounties for every jaguar killed in the belief this would protect livestock. By the 1960s, they were gone from the US. However in the last 20 years, some seven males have been documented in the Arizona borderlands, according the US Fish and Wildlife Service (FWS).

It’s not only jaguars: Predator control and hunting also extirpated mountain lions from the southwest and midwest. But these animals have since bounced back, and are repopulating regions as far north as the Dakotas and Kansas, Quigley told Motherboard.

The key to the mountain lion bounceback—and whether we could again see a viable jaguar population in the US—is the rugged, yet incredibly diverse, Sky Island region in southeastern Arizona and its connection to the wild northeastern Sonoran region of Mexico. Near Tucson, it’s one of the most biologically diverse areas in North America, where the temperate and tropical zones meet and two major deserts convene.

Camera traps in the Santa Rita Mountains, 60 miles north of US-Mexican border, have taken pictures of two male jaguars in the last couple of years, said Randy Serraglio, the Southwest conservation advocate at the Center for Biological Diversity. “There’s lots of good habitat they could re-colonize as long as there’s no wall,” Serraglio told Motherboard.

About one-third of the 3,200 kilometer border between the US and Mexico is already blocked by some kind of barrier, from barbed-wire fences and tall metal walls to big vehicle-stopping steel Xs. The more remote, rugged stretches remains unfenced for now, although Trump has long promised to complete the border wall and recently tweeted that he may use military funding to do it.

It’s not just jaguars that would be affected. In a letter published Monday in the journal Frontiers of Ecology and the Environment, two University of Texas at Austin biologists warn that Trump’s border wall would threaten endangered Texas plants and animals and hurt the region's growing ecotourism industry.

"Even small segments of a new wall on federal lands will devastate habitats and local recreation and ecotourism," said biologist Tim Keitt.

Jaguars are are considered near-threatened by the International Union for Conservation of Nature (IUCN), and habitat degradation is a major risk they face. Federal and state wildlife officials don’t appear to relish the opportunity to have jaguars in the US. “We’ve had to sue US Fish and Wildlife Service (FWS) to list jaguars as an endangered species. They’ve done nothing for jaguars except when forced to by court order,” Serraglio said.

Jaguars were listed as endangered in the US in 1997. Additional lawsuits were needed to force FWS to designate 1,200 square miles of southern Arizona and New Mexico as critical jaguar habitat, and to prepare a recovery plan as mandated under the Endangered Species Act.

The Jaguar Draft Recovery Plan was completed more than three years ago, said Quigley, who was one of the authors. The document, some 500 pages long, is still in review. “There’s not a lot of political support to move this forward,” said Quigley.

The final Jaguar Recovery Plan should be available by September 30, 2018, said Marit Alanen of the FWS Arizona Ecological Services Field Office. The recovery plan is an organizing tool for coordinating efforts to protect jaguars, but does not include any resources, Alanen wrote in an email. There is no specific reference to Trump’s border wall in the plan, but it does recommend human developments such as mines, dams, border infrastructure, urban development should be avoided, minimized, or mitigated.

The plan’s main recommendation was to help Mexico preserve its northern population of jaguars and to ensure safe corridors for these wild cats to freely move north. There is no hope of keeping jaguars in the US without a healthy Mexican population, Quigley said.

A jaguar in the Pantanal region of Brazil. Image: Panthera

Conservation groups and wildlife lovers have raised over $2 million to create the 55,000 acre Northern Jaguar Reserve in Sonora. Despite those efforts, building Trump’s “great, beautiful wall” would end any hope of jaguars remaining in the US, said Serraglio.

If the US isn’t willing to protect jaguars, other countries are trying. In a recent meeting, 14 of 19 nations with jaguars agreed that the big cats need help. They are developing a jaguar corridor plan from northern Argentina to Mexico.

“In the 1900s, there were 100,000 tigers [worldwide]. Now just 3,900 are left,” Quigley said. “Jaguars need help if they’re not to go the way of the tiger.”