Organ Pipe Cactus National Monument is a sprawling park in Arizona’s Sonoran Desert, home to a unique array of plants—including the cactus that gives the monument its name—and animals. The site also boasts a human history stretching back 16,000 years; ancient cultures used to travel through the region to obtain salt, obsidian and seashells from Mexico. But the Trump administration’s construction of a barrier wall along the southern boundary between Arizona and Mexico is putting the National Monument’s archaeological heritage at great risk, according to a National Park Service report obtained by the Washington Post.

As Juliet Eilperin and Nick Miroff report for the Post, the document identifies five sites that are threatened by the border wall construction, which began last month within Organ Pipe Cactus National Monument and seeks to replace existing vehicle barriers and pedestrian fencing with a continuous, 30-foot-tall steel bollard fence. NPS archaeologists also note that previous research has “identified and recorded 17 archaeological sites which likely will be wholly or partially destroyed by forthcoming border fence construction.”

President Donald Trump has repeatedly vowed to build 500 miles of the wall by the November 2020 election; at present, according to Zolan Kanno-Youngs of the New York Times, his administration has constructed 66 miles of fencing, primarily in areas where dilapidated borders already existed. Last month, the Washington Post’s Nick Miroff and Josh Dawsey reported that the President had “directed aides to fast-track billions of dollars’ worth of construction contracts, aggressively seize private land and disregard environmental rules” in order to get the project done.

Criticism of the border wall has often focused on its potential environmental impacts. Construction of the barrier, however, does not have to meet the requirements of federal environmental laws—including the Endangered Species Act, National Environmental Policy Act, the Clean Air Act, and the Clean Water Act—because the Department of Homeland Security waived the regulations in the name of “border security.” As is true of other areas where the wall is being built, activists are concerned about the ecosystems of Organ Pipe Cactus National Monument, which is an internationally recognized biosphere reserve.

“The lights that will be installed on top of the wall, blasted into the wilderness, the ground water being sucked up—it’s more than just a border wall,” Laiken Jordahl, a borderlands campaigner at the Center for Biological Diversity, tells Kanno-Youngs of the Times. “All of these activities will just increase the desertification of the region.”

And as the new report highlights, the National Monument’s archaeological heritage is also at risk of destruction. Stone tools, rock shelters and engravings have all been found there, and archaeologists are worried that the construction will damage unexcavated artifacts. Among the areas of concern are the Quitobaquito Springs, which are associated with a prehistoric trade route known as the Old Salt Trail.

Multiple indigenous groups have historic connections to the lands within Organ Pipe Cactus National Monument, including the Tohono O’odham and the Hia C’ed O’odham, according to the report. “We’ve historically lived in this area from time immemorial,” Tohono O’odham Nation Chairman Ned Norris Jr. tells Eilperin and Miroff. “We feel very strongly that this particular wall will desecrate this area forever. I would compare it to building a wall over your parents’ graveyards. It would have the same effect.”

For its part, the U.S. Customs and Border Protection says it has looked at “most” of the 22 archaeological sites identified in the NPS report, and that only five lie within the Roosevelt Reservation, the area where the wall is due to be erected, according to Eilperin and Miroff. Of those five sites, only one has “lithic scatter,” or the remains of cultural artifacts, and construction has not yet been planned for that location, CBP officials say.

But experts remain concerned about the CBP’s plans to complete its Organ Pipe Cactus National Monument barriers by January 2020. In its report, the NPS writes that it considers the entirety of Roosevelt Reservation to be “an area of great concern, whose cultural and natural resources are imperiled.” And Kevin Dahl, Arizona senior program manager for the National Parks Conservation Association, tells Eilperin and Miroff that under typical circumstances, the department would take steps to protect historic properties under its purview, even conducting excavations if necessary.