It’s a sunny morning along a stretch of border about 200 miles southeast of Phoenix. A grove of cottonwood trees with bright yellow leaves a few yards away marks the San Pedro River. It flows north from Mexico into Arizona.
Myles Trapagen, borderlands program coordinator with the group Wildlands Network, says Fray Marcos de Niza led the first Spanish exploration through here in the 1500s.
“Well this is ground zero for human and natural history in North America,” he said.
The bones of Colombian mammoths killed by hunters long before that have been found just miles away.
“Every species on the planet has had to have migrated at some point, and here we can really see the effects of this border wall at blocking this migration,” he said.
Species including everything from javelina and deer, to black bears, mountain lions — and even jaguars — rely on this stretch to access food, water and habitat in the U.S. and Mexico.
The border here used to be marked by a thin row of barbed wire. Today, the steel bollards of the 30-foot wall built under the first Trump administration cast thick black shadows across the dirt road.
Trump’s administration spent billions in defense money and other federal funding to erect the wall over more than 450 miles of borderland — including some 230 miles in Arizona.
Now, as conservationists expect more to come during a second Trump presidency, a new study looks at how animals have fared so far.
This is just the latest human-made border infrastructure in Arizona. Squat metal vehicle barriers began showing up in wilderness areas under former President George W. Bush in 2007, along with stretches of an 18-foot steel bollard wall.
But, Traphagen says, the Trump administration's 30-foot wall was different.
“After that went up, in landscapes that nobody anticipated that would happen, such as Organ Pipe National Monument, Cabeza Prieta, here at the San Pedro region, the San Bernardino Valley, it really hit home,” he said.
Traphagen and others have spent the last four years trying to figure out how, or if, animals have adapted.
Eamon Harrity, wildlife program manager with Sky Island Alliance, is crouched over a trail camera that’s set up right along the road next to the wall. It’s one of about 35 the group’s been monitoring since 2020 as part of the wildlife study with Traphagen.
"We’re at what is called a small wildlife passage, these were installed after construction, on federal conservation lands, so lands that are designated for wildlife or conservation,” he said.
It’s a hole the size of a sheet of printer paper at the bottom of the steel bollards. Trump administration contractors cut about a dozen of these into this 70-mile wall section after pressure from wildlife management agencies. They’re almost invisible to the untrained eye, but Harrity’s cameras even caught a female mountain lion and her kittens shimmying and squeezing through one of the tiny gaps to cross into Arizona.
“We’ve found that these openings are more beneficial than we first expected, with species like coyotes and javelina, racoon, [and] bobcats,” he said.
It doesn’t work for all species, though. Other footage has caught a bear pacing up and down the wall here for hours trying to get through. In another, a javelina gets so badly stuck trying to get through a section of bollards without the gap that it eventually dies of exposure.
All told, Harrity says their data shows less than 1 in 10 animals they film coming across the wall are actually able to cross it — compared to about 65% at vehicle barriers.
“We now have several years of data, many thousands of videos supporting what we’ve been saying, that the border walls are really effective at blocking wildlife, whereas the vehicle barrier, it’s not a perfect thing for wildlife … but generally speaking, wildlife are able to move through it — it brings weight to the argument we’re presenting to decision makers," he said.
He says hopes the data they have of successful crossings helps make the case for more openings.
“Even if the next administration isn’t in favor of building more wall, the wall is unlikely to come down for a very long time,” he said. “I think that if we can make that a more standard practice there may be opportunities to make the wall a slightly less of a blockade against wildlife.”
Trump has focused on tariffs and deportations so far, but conservationists like Sierra Club Borderlands Coordinator Erick Meza are already bracing to see more wall under his new administration.
“We’re pretty much expecting that Trump on his first day will declare the border a national emergency so that he can pull funding from other areas,” Meza said.
Meza’s group was part of a lawsuit that eventually allowed some flood gates built into the current wall to stay open year-round to help large animals cross more easily. It's one of several Trump-era wall suits that spilled into Biden’s presidency. Armed with the new data, the Sierra Club and other groups are now reaching out to federal agencies to ask for modification ahead of new construction.
“Working directly with whoever administers that specific type of land,” he said. “Whether it’s the Forest Service, or Fish and Wildlife.”
But, Meza admits, things are still uncertain. Customs and Border Protection recently announced plans to close several large gaps, including along a stretch of rugged, mountainous terrain in the Coronado National Monument, between the San Pedro River and the beginning of the Arizona trail. That stretch is set to begin in Arizona next year. And no one’s sure yet how negotiations will work under Trump.
Traphagen says this border wall era isn’t like the one back in 2017.
“It was generally a no-compromise approach .... they said, ‘don’t even agree to vehicle barrier," he said. "Times have changed, now we’ve seen the impact of 30-foot border walls, and now we have data that shows us that no, they’re an entirely different beast,” he said.
Now he says, they’re just trying to focus on fighting to preserve what’s been left unwalled.
“We’re trying to do our best to work within the system and the hand that we’ve been dealt so that we can do what’s best for wildlife,” he said. “And the places that are left are some of the best remaining places we have along the borderlands.”
Customs and Border Protection did not respond to questions about negotiations or plans for more wildlife crossings.
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