Here's What the Border Wall Means for Endangered Species—and the Hikers Who Love Them

Mexican gray wolves and other rare wildlife depend on a porous border for their long-term survival. Your dreams of seeing them may too.

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In the photographs trail cameras send back, the jaguars spotted in Arizona are often caught in profile, passing through on their way to somewhere else. Seven of the large felines (likely all roaming males) have been spotted so far, mostly in remote reaches of the state’s mountains. Invariably, they quickly disappear, leaving wildlife managers with only a guess about where they’ve gone: back to Mexico, where a conservation program run by the government and a coalition of NGOs has helped restore the species.

The United States forms the northernmost reach of jaguar territory, but they’ve been largely absent from the country for 50 years after being targeted by the same predator-killing campaign that led to the eradication of wolves and grizzlies across many western states.

The U.S. Fish and Wildlife Service currently has no plans to reintroduce jaguars, so natural migration is the species’ only hope of returning to the United States. And to do that, it needs something that’s politically explosive today: an open border.

Defenders of Wildlife says that if President Donald Trump moves forward with his promise to build a “beautiful wall” along the U.S.-Mexico border, he could singlehandedly end recovery for jaguars in the American Southwest.

“If we seal off the places where they’re currently moving from Mexico north to the U.S., it dooms any kind of natural repatriation of that animal to the United States—its original home,” says Bryan Bird, southwest program director for Defenders of Wildlife. The animals would have to be deliberately moved back to the country, a virtual impossibility in today’s political climate.

Jaguars are one of at least 89 endangered or threatened species, among them bighorn sheep, Mexican gray wolves, and Sonoran pronghorn, that make their home in the borderlands. They traverse what is now, for roughly 700 miles, an invisible boundary that crosses rugged mountains and runs through the Rio Grande.

Study after study has confirmed what might seem an obvious truth: Walling off that porous border would only put more pressure on those vulnerable species. “Barriers dissect, filter, eliminate or complicate movement and can influence small mammals and large mammals alike,” wrote researchers from the University of Bristol and the Zoological Society of London in one paper.

Isolating already limited populations worsens inbreeding and decreases their survival rate. Take, for example, the 113 Mexican gray wolves currently living in Arizona and New Mexico. Biologists have been sounding the alarm over the species’ dangerous level of inbreeding: they’re all roughly as related as siblings. While a mere 35 live in northern Mexico, those animals are on better genetic footing than their neighbors across the border, making exchange between the two populations critical to the subspecies’ survival.

“Both of these populations, even in a better-case scenario than they have, would not be viable on their own because they’re too small,” says Michael Robinson, with the Center for Biological Diversity.

In March, the Arizona Game and Fish Department trapped a young wolf that had traveled across the border, the second to do so this year. The first wandered through Arizona, New Mexico, and Texas before it “found the U.S. not to its liking and returned quickly to Mexico,” Jim deVos, assistant director of the department’s wildlife management division, told game commissioners during an April meeting. “So undoubtedly, it will happen again, particularly as their population grows.”

Exactly how a barrier at the border will affect the predators’ travel is hard to guess until a design is released, deVos says. But thinks that a compromise solution—a fence that still allows movement for animals—is possible.

“When a firm proposal comes out for a border fence, then all of the agencies involved—Homeland Security, Border Patrol, and the wildlife and natural resource agencies—need to sit down and develop a strategy that enhances border protection but maintains some crucial wildlife crossings, and we believe that that’s a feasible proposition,” he says.

“I think the important thing is that this view of the wall that would stretch from the Gulf of Mexico to the Pacific Ocean without break—I think isn’t truly reflective of reality.”

DeVos isn’t the only one who thinks a coast-to-coast fence is unlikely. Secretary of the Interior Ryan Zinke has conceded that the region’s complicated geography will force the federal government to make compromises. He points to the Rio Grande: The U.S. government is unlikely to wall off the river and cede it to Mexico, and unable to build a wall on the Mexican bank. (He’s also declared he’ll waive jaguars’ protections under the Endangered Species Act to construct a wall through its critical habitat). John Kelly, secretary of homeland security, has expressed similar doubts.

While conservation advocates might see hope in this shift, there are lots of ways to erode a habitat. Increased border patrols and the new roads they’d require and even drone fly-bys could all make the region less welcoming for wildlife and humans along the 623 miles of federally-managed borderlands. Those lands include backpacking hotspots like Big Bend National Park and Organ Pipe Cactus National Monument.

“It would slowly erode the wildness of this part of the country,” Bird says. “You’d be spoiling one of America’s national treasures, and there’s probably no real security risk.”

These spaces house diverse ecosystems and astonishing biodiversity precisely because of their rugged and foreboding geography, which also makes them fatal to hundreds of would-be migrants each year.

“We’re talking about a destruction of a region of sublime wild beauty, severing it as if we were just cutting it apart with an ax,” Robinson says.

The border wall’s final form is still in flux, however. Former Arizona governor and Secretary of Homeland Security Janet Napolitano called for a border plan that relied on technology: ground-based sensors, radar and drones. DeVos, with Arizona Game and Fish, says he sees “every opportunity” for a fence that makes use of virtual barriers, including the underground sensors and camera towers already in use.

The Lower Rio Grande Valley National Wildlife Refuge, a complex that occupies the easternmost 275 miles of the Rio Grande and the beach where it empties into the Gulf of Mexico, is a typical example of the habitat that a border wall would affect. The refuge is believed to house 19 federally threatened and endangered species, 57 state-protected species, 776 plant species, 50 mammal species, 29 varieties freshwater fish species, and 65 reptile and amphibian species. It’s widely considered one of the most biologically diverse in the entire refuge system.

The Lower Rio Grande was closed to the public until 2000, when just less than half of it was made available for a hunting and bird watching. Its amenities are still “rudimentary,” says refuge manager Bryan Winton: there aren’t bathrooms or improved trails. Hikers use an existing system of rough roads.

“There’s a lot of opportunity to get out and away from the sounds and sights of development in a fast-growing area,” says Winton. But that space is also often crowded by border patrol agents searching for the drug smugglers and human traffickers who occasionally cross into the United States here.

Winton says he’s hopeful a border fence would reduce illegal activity. But it would also bring more agents and more vehicles, meaning more disturbances for the sea birds and critically endangered Kemp’s Ridley sea turtles that nest on the refuge’s beaches and hummocks. “It’s a tradeoff that we’ve learned to live with here on the border,” he says.

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