President Trump rolled back federal protections for two national monuments in Utah Thursday, reversing the stance of former presidents who previously opted to keep them sacred from extractive industries like drilling and mining.

Trump called for a roughly 85 percent cut to the sprawling 1.35 million-acre Bears Ears National Monument and a 50 percent cut to the Grand Staircase-Escalante National Monument, saying former presidents took advantage of a more than century-old law to “lock up hundreds of millions of acres of land and water under strict government control.”

The monuments had been designated as national monuments by former President Barack Obama and former President Bill Clinton respectively, under the Antiquities Act, which allows presidents to unilaterally designate monuments without congressional approval.

Trump’s decision to remove federal protections on parts of the lands paves the way for commercial activities like drilling, logging, and mining to take place. The move was quickly chastised by Native American tribes, activists, and even policymakers, many of whom warned of potential lawsuits.

“This is a sad day for indigenous people and for America. However, we are resilient and refuse to allow President Trump’s unlawful decision to discourage us,” said Jonathan Nez, vice president of Navajo Nation. “We will continue to fight in honor of our ancestral warriors who fought for our way of life, for our culture, and for our land, too.”

Trump’s plan to remove national monument status from hundreds of thousands of square miles of land is the first time national monuments have been shrunk so significantly. Former Interior Secretary Sally Jewell told VICE News it could mean all monuments could be threatened after a president’s four-year term expires.

“If the challenges to President Trump’s actions fail, what this means is this vital piece of legislation that has enabled us to protect places that we take, as part of the United States, as permanently protected, may not be permanently protected at all,” Jewell said.

While the president has the authority to designate national monuments, Congress can designate national parks, and the Secretary of the Interior can designate a wildlife refuge, according to Jewell.

“[T]here are multiple designations but only the national monument is the purview exclusively of the president,” said Jewell. “And it was designed to be able to take fast action when Congress wasn’t acting to protect treasures among our landscape — cultural, historic and natural that otherwise would be vulnerable to destruction in some way.”

There are four other national monuments that could possibly be next. In August, Trump’s secretary of the interior, Ryan Zinke, wrote a report obtained by the Washington Post that recommended revising the boundaries or modifying 10 national monuments. These are the ones besides Bear Ears and Grand Staircase-Escalante that were recommended to be shrunk:

Gold Butte, Nevada

The Gold Butte National Monument in Clarke County, Nevada spans over 296,000 acres of red sandstone and canyon, and was designated by former President Obama in 2016. Zinke’s memo recommended Gold Butte to be shrunk in order protect “historic water rights.”

Cascade-Siskiyou, Oregon and California

The 113,000- acre Cascade-Siskiyou landscape was designated as a national monument in 2000 by former President George W. Bush. Zinke’s memo recommends the boundaries should be revised to allow for “sustained-yield timber production.” It does not specify by how much.

Rose Atoll, Pacific Ocean

The Rose Atoll, a combination of underwater and land in American Samoa, was designated by former President Bush in 2009. Zinke’s memo, like for the Pacific Remote Islands, says the boundaries should be changed to allow for commercial fishing.

Pacific Remote Islands, Pacific Ocean

The Pacific Remote Islands, a cluster of U.S. territories in the center of the ocean, filled with ecosystems and coral reefs, was made a national monument in 2009, and then later expanded under Obama in 2015. The islands have largely been immune to degradation because fishing lanes avoid them, but Zinke’s memo says the boundary should be changed to allow commercial fishing.