President Donald Trump signed an executive order today (April 26)—the 27th in his nearly 100 days of presidency—directing Interior Secretary Ryan Zinke to review the Antiquities Act and prior national monument designations (starting from January 1, 1996) that are at least 100,000 acres in size.

“I’m doing it because it’s the right thing to do,” Trump said today at the signing.

Zinke was clear during today’s signing that the order would not strip any monument of a designation and would not remove their environmental or conservation regulation. Congress enacted the Antiquities Act in 1906 under President Teddy Roosevelt to protect historic ruins or monuments from human influence or damage. This act gave the president the power to declare lands as historic landmarks or objects of historic or scientific interest.

Zinke expressed disapproval, in a press briefing yesterday (April 25), of the way national monument designation worked prior to this order. The president had the power, without public input, to designate monuments. The point of this executive order, Zinke said, is to “give states and local communities a meaningful voice in the process.”

Zinke went on:

“[I]n some cases, the designation of the monuments may have resulted in loss of jobs, reduced wages and reduced public access. And in the case of sign public land use, we feel that the public, the people that the monuments affect, should be considered. And that’s why the President is asking for a review of the monuments designated in the last 20 years to see what changes, if any, improvements can be made, and give states and local communities a meaningful voice in the process.”

The United States currently has about 157 national monuments, according to the National Park Service. Former President Barack Obama established 29 throughout his two terms and enlarged four already existing monuments. The most controversial designation was one of his last, the Bears Ears National Monument.

The monument is 1.35 million acres large and sits in southeastern Utah, a region of the United States that Zinke said would get extra attention in his review and where, he says, legislators believe that the Antiquities Act is abused.

Bears Ears is where the Clovis people hunted mammoths, ground sloths and other now-extinct megafauna. It is land the ancient Native Pueblo people roamed to build their signature cliff dwellings. Rock walls of the Bears Ears National Monument are covered in pictographs and petroglyphs telling stories that date back 5,000 years. In addition, it is a site considered sacred to Native and tribal people.

So while many tribal governments and Native tribes supported protecting Bears Ears, industry interests did not. The historic land is rich in oil, natural gas and uranium—all of which is off-limits under its national designation. Now, environmentalists are opposing the president’s order that might change how this site (and others) is protected.

“Donald Trump’s latest executive order furthers his vision for our public lands: a polluted wasteland crammed with oil rigs and strip mines as far as the eye can see, “ said Lukas Ross, energy campaigner with Friends of the Earth in an emailed statement.

Trump explicitly mentioned Bears Ears during his announcement today, saying he has heard it’s “beautiful” but the Antiquities Act “does not give the federal government unlimited power to lock up millions of acres of land and water, and it’s time we ended this abusive practice.”

Zinke must provide an interim report to Trump within 45 days and a final report within 120 days.