Cut down a saguaro cactus in Arizona and you can face years in prison. But over the past several weeks, work crews have been destroying dozens of the protected cactuses, which can live for 200 years, to build a new wall on the southwestern border.

The remains of chopped-up saguaros are now visible along a swath of the Sonoran Desert in southern Arizona, part of what Native American leaders warn is a range of environmental and archaeological threats posed by the Trump-administration’s scramble to build the wall.

Work along the border, according to tribal leaders of the Tohono O’odham Nation who live on both sides of the border, is blasting ancient burial sites and siphoning an aquifer that feeds a desert oasis where humans have slaked their thirst for 16,000 years.

The outcry by tribal citizens reflects the latest phase in the quarrelling over the border wall, after federal courts allowed the Trump-administration to speed construction by waiving dozens of laws, including measures protecting endangered species and Native American burial sites. Federal officials have cited Donald Trump’s national emergency declaration in 2019, aimed at curbing unauthorised immigration, as justification for the waivers.

Dynamite blasts are now echoing throughout lands assigned the highest degree of permanent protection by Congress as workers lay the foundation for the wall. To mix concrete, crews are drawing water from a spring near where ancient bone fragments were unearthed last year.

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The work is occurring at sites inside the Organ Pipe Cactus National Monument, which president Franklin D Roosevelt established by proclamation in 1937. The area has been designated by UNESCO, the United Nations cultural organisation, as an internationally protected biosphere reserve.

“To state it clearly, we are enduring crimes against humanity,” said Verlon M José, governor of the Tohono O’odham in northern Mexico and a former vice chairman of the tribal nation on the US side of the border.

“Tell me where your grandparents are buried and let me dynamite their graves,” said Mr José, emphasising how visceral an issue the blasting has become among O’odham-speaking peoples. “This wall is already putting a scar across our heart.”

The Border Patrol, which is overseeing the wall construction within the national monument, is hitting back at such assessments. John Mennell, a Border Patrol spokesman, disputed the claims by O’odham leaders and said that “no biological, cultural or historical sites were identified within the project area.”

In a statement, Mr Mennell added that the agency has “a history of voluntary compliance where it is necessary to minimize impacts” and that workers were destroying only cactuses “determined not to be in a healthy enough state to be relocated.”

At a congressional hearing about these activities Wednesday, Rep. Ruben Gallego, Democrat for Arizona, compared the blasting at sites held to be sacred by Native Americans to the war crime of destroying sacred cultural sites during international conflicts.

He also accused federal authorities of “gaslighting” by contending that the construction work was aimed at preserving lands near the border. The government has suggested that building a wall would prevent migrants from trampling over the desert in vehicles and on foot.

The White House and Department of Homeland Security did not send representatives to the hearing. On the same day as the hearing, the Border Patrol and Army Corps of Engineers invited reporters to view a controlled detonation during border wall construction.

After grievances by O’odham citizens intensified in recent months, Representative Raúl M Grijalva, a Democrat representing southern Arizona, homed in on the use of explosives at an area of the monument that many O’odham consider a sacred indigenous site.

Citing O’odham leaders, Mr Grijalva said in a video posted on Twitter that the site, known as Monument Hill, “is the resting place primarily for Apache warriors that had been involved in battle with the O’odham, and then the O’odham people in a respectful way laid them to rest on Monument Hill.”

Objections to the border wall are now multiplying from the some 28,000 enrolled members of Tohono O’odham (pronounced To-HO-no AW-tham). Many live in the tribal nation’s reservation in Arizona, which is near Organ Pipe, while about 2,000 others live in an adjacent area of northern Mexico.

Before the US conquest of Arizona in the 1840s, the O’odham homeland encompassed Organ Pipe as well as much of southern Arizona. The border sliced through these lands first as a result of the Mexican-American War and then the Gadsden Purchase in 1854.

The United States-Mexico border wall as seen in Organ Pipe National Park south of Ajo Arizona on February 13 2020 (Sandy Huffaker AFP)

Now the stretch of border where work crews are blasting rock and building the wall is creating a gash through the middle of this revered stretch of desert. On a recent day in February, it was possible to see the uprooted remains of an organ pipe cactus, the protected and rare species that resembles a pipe organ.

The Border Patrol said workers had relocated hundreds of cactuses within the park, but tribal leaders and environmental activists have documented multiple examples of uprooted cactuses left to decay under the desert sun.

Serving as testament to the rise and fall of nations in the borderlands, some of the cactuses destroyed by work crews for Nebraska construction giant Kiewit were alive before the international border even existed in this part of the Sonoran Desert.

The national monument sits at the heart of an ancient indigenous territory known during colonial times as the Papaguería, according to the Organ Pipe monument’s administrative history, with petroglyphs and rock art scattered throughout the site.

In addition to providing the name of the tribal nation, the word “O’odham” roughly means both “saguaro” and “person,” reflecting how O’odham peoples relied on the cactuses as a fruit, cooked over mesquite or fermented into ceremonial wine.

“All of the desecration to build this wall constitutes a very personal attack on us,” said Amber Ortega, an O’odham student who lives near the monument. “Why have laws when there is no accountability for these abuses?”

To advance the border wall project, the Trump administration has used a little-known section of the Real ID Act that allows the Department of Homeland Security to waive compliance with federal law to expedite construction of barriers along the border.

Among the laws being waived is the Endangered Species Act. Laiken Jordahl, a former National Park Service employee who surveyed the wildlife of Organ Pipe, said the at-risk animals in the park include the lesser long-nosed bat and the Sonoran pronghorn, one of the most critically endangered wildlife species in the United States.

“This project will change the evolutionary history of this landscape, impacting species migrations, seed dispersal, the flow of water,” said Mr Jordahl, who now works for the Center for Biological Diversity, an organisation focused on saving imperiled species. “It’s painfully obvious that we’re destroying what this place was established to protect,” he said.

The push to build the wall stands in contrast to previous infrastructure projects on the border.

During construction of a section of border wall in 2008, the Bush administration trucked in water for construction use instead of extracting water from the aquifer feeding the Quitobaquito spring.

Cacti in the Arizona landscape (Robert Murray/Unsplash)

Authorities were hoping to preserve the Quitobaquito oasis, where O’odham people had lived for generations. Among them was a family that had remained at the site for two decades after the monument was created, until the National Park Service forced them to leave, according to Jared Orsi, a historian at Colorado State University.

Last year, bone fragments found near the spring were determined to be from the Classic Hohokam Period, which lasted from AD 300 to 1,500. The National Park Service said it planned to repatriate the fragments to the Tohono O’odham Nation.

Now workers at the site are pumping water from the aquifer beneath Quitobaquito to mix cement and to water down dirt roads around construction sites. That could endanger not just the spring’s existence but species in its waters such as the Quitobaquito pupfish and Sonoyta mud turtle, according to the National Park Service.

Mr Mennell, the Border Patrol spokesman, said park officials were monitoring the spring to “identify any significant changes in water levels.” He said no groundwater would be used within 5 miles of Quitobaquito.

“People would be unhinged if this were happening someplace else,” said Vana Lewis, a Tohono O’odham teacher. “This fits into a pattern of trampling over our rights on land that was taken from us and was ours since time immemorial.”

Around the work sites that are strewn with felled cactuses, the occasional tourist shows up to snap pictures of the wall going up. Signs provide warnings about nearby blasting. Border Patrol agents still search for migrants crossing into the wilderness.

On a recent day, Border Patrol agents and employees from the National Park Service picked up a Venezuelan, Coromoto Ureña, who had crossed with her 4-year-old granddaughter, María José, at a remote spot near Quitobaquito.

“Our only choice was to come this way,” said Ureña, a resident of San Cristóbal Venezuela, clasping the hand of her granddaughter while they were being detained. Ureña said they were hoping to reunite in the United States with her son, who lives in Denver.

O’odham leaders have been grasping for ways of stymieing the project. Ned Norris Jr., chairman of the Tohono O’odham Nation, requested this month that the Defense Department halt diversion of an estimated $3.8 billion in military funds the administration hopes to use to pay for the wall.

As the blasting goes on, anger is building around the country from some members of Congress and their constituents. Tammy Gitter, a yoga instructor from Los Angeles, drove to Organ Pipe to witness what she regarded as a disastrous event.

“I didn’t go to New York for 9/11 or New Orleans for Hurricane Katrina, so I felt I had to come here,” said Ms Gitter

“This tragedy is being carried out in our name,” said Ms Gitter, tears starting to swell in her eyes as she gazed at Quitobaquito’s waters. “The whole thing just enrages me.”