Portions of a national monument held sacred by some indigenous Americans were destroyed this week to make space for President Donald Trump’s signature US-Mexico border wall.

The Organ Pipe Cactus National Monument is a designated national monument and a UNESCO biosphere reserve on Arizona’s southern border, about 25 miles west of Tuscon. Home to the organ pipe cactus, the reserve also contains burial sites belonging to the Tohono O’odham Nation, as well as sites revered by other indigenous groups.

This week, as the Intercept’s Ryan Devereaux first reported, crews commissioned by Customs and Border Protection (CPB) began blasting through the park’s Monument Hill to make way for a section of the border wall, allegedly without consultation from the O’odham Nation.

“There has been no consultation with the nation,” Rep. Raúl Grijalva (D-AZ) told CBS News. “This administration is basically trampling on the tribe’s history — and to put it poignantly, its ancestry.”

The construction was authorized in May by the Department of Defense, which oversees civil defense-related building contracts, when it awarded $891 million to contractors for wall construction at Organ Pipe and the nearby Cabeza Prieta National Wildlife Refuge.

CBP officials describe the work as “controlled blasting” needed to erect a 30-foot steel wall across 43 miles of desert. Monument Hill, also called Monument Mountain, stands within this stretch of desert, and is part of the Roosevelt Reservation, a sixty foot-wide swathe of public land across the southern border. Blasting is expected to take place intermittently for the next month, according to the Associated Press.

The construction only marks a small part of the work being done across the US-Mexico border, the cost of which has so far totaled about $18.4 billion. Part of that total is a $3.5 billion sum the White House plans to pull from military counter-drug spending, up from $2.5 billion last year, and $3.7 billion that will be rerouted from funds earmarked for military construction funding.

The O’odham and environmentalists have been unsuccessful in their efforts to stop construction

The portion being cleared inside the Organ Pipe park is directly adjacent to O’odham burial sites, according to Grijalva. Indeed, crews working in the area last year found ancient human bones, suggesting that their work has already touched upon indigenous burial sites. According to a memo obtained by the Washington Post, those bones could be just the beginning: The National Park Service found that up to 22 archaeological sites could be damaged by the construction process.

O’odham leaders have had difficulty fighting the construction given the land no longer officially belongs to the tribe. However, O’dham Nation chairman Ned Norris, Jr., has argued that the area should fall under the auspices of the Native American Graves Protection and Repatriation Act, which is meant to protect indigenous burial sites and return important cultural items to affiliated tribal entities.

“The Nation categorically opposes the barrier construction projects, because they directly harm and threaten both the lands currently reserved for the Nation and its ancestral lands that extend along the international boundary in Arizona,” Norris wrote in part. to the CBP last November.

When O’odham representatives and Grijalva visited the site in January, Norris vowed to continue fighting the construction.

“Regardless that it isn’t within our reservation boundaries anymore, but it’s clear, we have inhabited this area since time immemorial,” Norris said, according to the Arizona Republic. ”They’re our ancestors. They’re our remnants of who we are as a people, throughout this whole area. And it’s our obligation, it’s our duty to do what is necessary to protect that.”

The work has raised concerns among environmental activists as well — a group of whom sued to try to stop construction. That suit did not suspend progress.

The monument was designated a biosphere reserve in 1976 in order to preserve its unique desert ecosystem. Environmental advocates have expressed concerns over the impact the wall will have on migrating animals and rare cactuses. Two endangered species, the Sonoyta mud turtle and Quitobaquito pupfish, make their homes in a desert oasis within the park — activists fear the construction could do irreparable damage to their already fragile populations.

CBP officials dismissed these fears, and have said an “environmental monitor” will present during the clearing work.

And although biosphere reserves and Native American sites do have special protections, the Trump administration can bypass environmental and tribal sovereignty concerns by invoking to the REAL ID Act of 2005, which allows the federal government to ignore certain laws in the interest of national security. The Trump administration has used that waiver at least 16 times, according to Grijalva.

The Trump administration has long ignored social and environmental concerns about the US-Mexico border wall

Social and environmental costs have been pointed out to the Trump administration throughout the process of realizing the president’s signature 2016 campaign promise, and those concerns seem to have little effect on the project’s progress.

Vox’s Eliza Barclay and Sarah Frostenson have reported on the significant ecological impact of border wall construction, beginning with the existing 654 miles of walls and fencing that were already on the US-Mexico border when Trump took office. As they wrote:

The existing barrier has cut off, isolated, and reduced populations of some of the rarest and most amazing animals in North America, like the jaguar. They’ve led to the creation of miles of roads through pristine wilderness areas. They’ve even exacerbated flooding, becoming dams when rivers have overflowed.

Proposed construction in Texas would cut through a federal wildlife refuge, a state park, the National Butterfly Center, and more Native American grave sites, they reported. Such damage is not merely environmental, they add, but also potentially political, threatening conservation-based partnerships with Mexico that strengthened the overall relationship between the two nations, according to one conservationist they spoke to.

But immigration — not conservation or reparations — has been this president’s signature issue since before he was elected. It is an issue his base is passionate about, and one he can claim he has been successful in implementing promised policy changes, from reducing the number of legal and undocumented immigrants entering the US to getting sections of the wall built. With November’s election right around the corner, pushback on one portion of his border work — especially from indigenous Americans and environmentalists, not exactly his base, isn’t likely to give the Trump administration much pause.