RODEO, N.M. – When ranchers and environmentalists were fighting one another over the future of western rangeland a generation ago, a group of families here along the U.S.-Mexico border joined to seek a middle path.

They founded the Malpai Borderlands Group, working with big-money foundations to put conservation easements on tens of thousands of acres. The agreements protected critical desert habitats from development and industry while providing tax breaks to allow traditional ranching to continue. The model was hailed as a breakthrough.

William McDonald, a fifth-generation Arizona cattleman who led the effort, received a MacArthur “Genius Grant” in 1998, citing “his leading efforts to create ecologically responsible cooperation among government regulatory agencies, conservationists, scientists, and commercial ranchers in the West.”

Today, a few miles from the site where bulldozers and excavators are building President Donald Trump’s border wall, McDonald, 67, said he feels defeated and filled with regret. Decades of political wrangling and consensus-building – his life’s work – are being flattened.

“I feel like I’ve let down the generations to come, because we’re going to have that ugly scar out here,” McDonald said. “It just makes me sick.”

Though Trump often has depicted border residents as the biggest beneficiaries of his signature project, the arrival of construction crews and heavy equipment to this region has brought bitterness and resignation to some residents. The wall – which then-candidate Trump promised en route to defeating Hillary Clinton in 2016 – is turning longtime friends against one another and is dramatically altering one of the wildest and most storied areas of the American West.

The Malpai founders insist they support strong border security, pointing out their many years of cooperation with the U.S. Border Patrol to report illegal activity and grant access to their properties.

What they oppose is the decision to put the massive steel barrier here, where they claim it is unnecessary, wasteful and destructive. Border Patrol officials said the new fencing will safeguard the country for decades to come, but many of the ranching families who live here – and who have spent their lives trying to strike a balance between wildlife and cattle, tradition and regulation – claim they have been pushed aside.

The 20-mile stretch of border east of Douglas, Ariz., where crews are working, was once among the busiest places for illegal crossings. But it has been quiet for years, with just a few arrests each month, the families said. Their claims are supported by U.S. Customs and Border Protection reports that show the area is not a priority for the Border Patrol; it was not among the top 15 locations where the agency said it urgently needed new barriers.

The Trump administration is building here anyway. The president is now running for reelection on a promise to complete more than 500 miles of new border fence by early next year. While progress has been extremely slow in Texas, where nearly all of the land is in private hands, this area along the New Mexico-Arizona border has seen the pace of construction accelerate.

The Malpai region has few property owners, relatively flat terrain and easy access to large tracts of land under federal control. Though it might not be a top security priority, it is one place the Trump administration can build quickly.

Roy Villareal, chief of the Border Patrol’s Tucson sector, acknowledged that the Malpai region has been quiet from a law enforcement perspective in recent years, but he said it would be a mistake to assume it will remain that way.

“What I do not want to have happen is a resurgence, and once again have us become the epicenter of the Southwest border,” Villareal said in an interview. “When we look at the placement of wall, we take into consideration our past, our current needs, and start looking at the future. … The border is dynamic, and can change in a heartbeat.”

McDonald and other founding members of the Malpai group are skeptical of the Border Patrol’s security arguments. They see political expediency instead.

The group had worked closely with federal agencies for more than two decades to align interests and minimize conflict, overcoming decades of mistrust toward the government. That relationship ended up lulling the group into a false sense of trust, McDonald said.

Border Patrol officials had assured the Malpai families that their span of border was not a priority for the barriers, McDonald said. By the time the agency informed the group of the construction plans, it was too late to challenge the government.

“I should have spoken up earlier,” McDonald said during an interview in the living room of his home a mile from the border. “Maybe if we had fought them politically, we could have made a difference.”

The late Sen. John McCain, R-Ariz., had been a friend, McDonald said, and was a guest twice at his home. McDonald turned toward the window, where the winter sun was slipping below the canyon walls, his boots shifting on the plank floor. “If McCain were still here, he’d have stopped that wall,” he said.

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Malpai co-founder Warner Glenn was hunting in the Peloncillo Mountains near the border in 1996 when he followed his baying hounds to a rocky outcropping above a ravine. Glenn was expecting a mountain lion, but the animal was much larger, with black spots.

He took out his camera, and became the first person to photograph a wild, living jaguar on U.S. soil.

The photo was a watershed moment in western conservation, and for Glenn and others, it was an affirmation that the Malpai project was working to protect a special place. “The jaguar was a sign that we were doing the right thing,” he said.

The mountain range, which straddles the Arizona-New Mexico line, is among the few that connect to the much-larger western Sierra Madre mountains of Mexico. For the elusive jaguar and other North American megafauna, the range is a crucial biological corridor, allowing animals to migrate north through remote areas with few people or roads.

Glenn’s jaguar photo, and sightings and remote-camera footage of big cats since then, have thrilled conservationists who argue that the American West can be brought back from decades of overgrazing, mining and habitat loss.

But the same features that make the Peloncillo range attractive to roaming jaguars also appeal to drug smugglers. Within a few years of Glenn’s sighting, Mexican traffickers were sending marijuana couriers with backpacks through the mountains nightly.

After delivering their loads at highway drop-off points north of the border, the smugglers often would hike back along the same mountain trails. Some would raid homes and ranches along the way before slipping back into Mexico. Thefts, vandalism and break-ins became routine.

If Glenn’s encounter with the jaguar was an electrifying moment for the Malpai conservation effort, the low point came in 2010, when Rob Krentz, one of the group’s members, was killed on his family’s ranch by a suspected trafficker near Apache, Ariz.

Krentz’s slaying shattered the notion that the violence of Mexico’s drug war would remain south of the border. Krentz had been warning authorities that the migrants coming through the area were no longer primarily seasonal laborers looking for work, noting that more sinister elements were moving in.

After Krentz, 58, was found slumped in his four-wheeler with gunshot wounds, Glenn and a neighboring rancher tracked a single set of footprints southbound toward Mexico through a wash. They stopped where the footprints crossed the border. Krentz’s attacker was never found.

His son, Frank Krentz, still raises cattle on the family homestead where his father was killed. He is one of the Malpai ranchers who support Trump’s plan to build the wall here.

Now 37, Krentz said he grew up riding horses and running all over the mountains, describing his childhood as a time of total freedom. That world was lost with his father’s killing, he said, and it is something that he said his children will never experience.

Krentz acknowledged that there have been tensions among the Malpai families about the border wall, but he said other members are respectful of his views. He said he agrees with the critics who claim the barrier will not stop determined border-crossers from getting through, but he said it will be worthwhile if it brings a degree of security and peace of mind.

“The Malpai are trying to keep open spaces, but open spaces are a view-scape,” Krentz said. “Why should citizens be scared because one tool wasn’t used?”

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The Krentz killing was a catalyst for conservatives pushing tougher border security. Within weeks, Arizona legislators approved the “show me your papers” law, Senate Bill 1070, giving police the ability to demand proof of residency during traffic stops and other routine encounters. It was one of the most restrictive state immigration laws in the country.

The slaying also changed the relationship between the Malpai ranchers and Border Patrol. Supervisors became far more attentive to their concerns, deploying more agents and increasing patrols, McDonald and other ranchers said. It was a new period of close cooperation.

The government also added more “vehicle barriers,” which were fashioned from old railroad tracks. The barriers allowed wildlife to travel freely, but they made it nearly impossible for smugglers to drive across the border.

“The vehicle barriers cut drive-throughs by 80 percent,” Glenn said.

But the biggest change came when several western states began decriminalizing marijuana. The market for lower-quality Mexican-grown cannabis shrank, and Malpai families saw fewer backpackers trekking through the Peloncillos.

The cartels were switching to harder drugs – methamphetamine, cocaine and opioids – typically bringing those loads through official vehicle entry points in hidden compartments.

By the time Trump launched his presidential campaign with the promise to build a border wall in 2015, many of the threats that drove his argument were beginning to fade, at least in the Malpai region.

McDonald thought the group’s close cooperation with Border Patrol would spare the region from having a section of wall. The group was confident that the government would look at the falling arrest and seizure numbers for that stretch of border and see no need for a 30-foot-barrier with floodlights across the desert.

“But everything from D.C. just comes in a one size fits all,” McDonald said.

Rich Winkler, the current director of the Malpai group, whose family’s ranch backs up against the Peloncillo range, said he, too, is a proponent of strong national security. And he does not question the need for tall fences along other parts of the border.

“I’m sure it’s appropriate in urban areas,” Winkler said. “But what is its effectiveness out here?”

Winkler wonders how any trafficker motivated and daring enough to hike for days through the mountains with little food or water would let the barrier be much of an obstacle given that it can be scaled with ladders and ropes or cut with household tools.

Glenn said his family reluctantly agreed to sell groundwater to the wall contractors, worried that if it refused, the government would use its eminent domain powers to drill a well and take the water.

The water that contractors are using to make concrete comes from the same aquifer that feeds artesian springs and seeps onto the San Bernardino National Wildlife Refuge, which was created in 1982 to protect the region’s largest natural wetland. In recent weeks, remote video cameras on the refuge have captured puma, bobcat, wild turkey and other species streaming through the last remaining gaps in the barrier before construction crews finish the job.

At the southern end of the Glenn family’s ranch nearby, there is now a construction site spreading through the ocotillo and mesquite, humming with heavy equipment. Tractor trailers with Texas license plates rumble along the dusty Geronimo Trail road loaded with new steel panels.

Kelly Kimbro, Glenn’s daughter and a hunting guide like her father, said the structure will cut off wildlife, threatening decades of conservation efforts. And in a place of open vistas, where there are few visible signs of human impact, the project has inflicted a kind of psychological injury bigger than the structure itself.

“There are places that should have a wall,” Kimbro said. “And there are places that should never have one. It breaks my heart to see it.”