Environmentalists are sounding the alarm about the destruction of an ancient cottonwood grove along the Arizona-Mexico border, as construction crews work on the Trump administration’s latest border wall project.

The grove is located in Lochiel, Arizona, a tiny town some 25 miles east of Nogales. One protester was arrested there on Monday, as construction crews moved in on the trees.

Video from that morning shows a man talking to a construction worker in a bright vest and a Border Patrol agent. The thick, gray trunk of a cottonwood tree is toppled over behind them, and the pronged metal bucket of a earth moving machine is nearby.

Erick Meza, borderlands program coordinator with the Sierra Club, says four trees sit right along the border in Lochiel and each are over 100 years old. He says all but one have been downed by construction workers — all without protection measures outlined in a letter from Border Patrol.

“And even after they were told about this letter, they didn’t want to listen,” Meza said. “They start using some of the heavy machinery they have and just taking down the trees.”

In the June 18 letter, shared in a press release from the Sierra Club, the agency says the four trees are within a 60-foot strip of federal land along the border known as the Roosevelt Reservation and will be removed for the border wall. The agency says environmental monitors will assess the trees beforehand be present during the removal process.

“If construction activities will result in the disturbance or harm of a migratory bird, then coordination with the appropriate federal agencies will occur,” the letter reads. “The contractor will also establish a buffer zone around active nests until nestlings have fledged and abandoned the nest.”

Meza says neither measure was taken this week. He says his organization also sent video of nesting activity they documented in the trees recently to Border Patrol, but never received a response.

“We’re just kind of really upset and frustrated that they didn’t keep up their word,” he said.

The Santa Cruz County Sheriff’s Office says deputies responded to a call from Border Patrol and arrested one protester Monday on a third-degree trespassing charge, after he refused to leave the construction site. He was released Monday and faces court later this week.

Late last year, the Trump administration awarded roughly $1.4 billion to construction firm Fisher Sand and Gravel Co., which built 19 miles of new and secondary border wall in Arizona, along with 136 miles of detection technology.

The contract is part of a multibillion-dollar project announced by the administration last year to build a so-called Smart Wall system in Arizona and Texas — a secondary barrier announced that would include lights, surveillance and a physical structure. Construction is slated for large swaths of public land in Arizona, including some that already has the 30-foot steel bollard wall built under the first Trump administration.

Neither CBP nor Fisher Sand and Gravel Co. responded to questions about the cottonwood removal or the June 18 letter.

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