President Donald Trump signed two presidential proclamations today that will substantially shrink two national monuments in Utah.

Documents indicate the proclamations will shrink the Grand Staircase-Escalante and Bears Ears national monuments by nearly 50 percent and more than 85 percent, respectively. It’s the first time a president has reduced the size of a national monument in more than 50 years.

Mr. Trump announced the decision from Utah, where he told a crowd that the national park monuments had “locked up hundreds of millions of acres of land and water under strict government control,” including “harmful restrictions” on hunting, grazing and economic development.

How did we get here?

In late April, Interior Secretary Ryan Zinke launched a review of 27 national monuments created in the last two decades, a response to a pair of executive orders from Trump requesting an assessment.

Trump called the creation of Bears Ears national monument by his predecessor President Barack Obama in 2016 a “massive federal land grab” that “should have never happened.”

In August, Zinke submitted a report to the president with recommendations, including cutting the acreage of Bears Ears and Grand Staircase-Escalante.

The Department of the Interior has not made public exactly how the monuments will be reduced. But according to the leaked documents, the rollback would:

Shrink the Grand Staircase-Escalante from 1.9 million acres to 997,490 acres

Reduce Bears Ears from 1.35 million acres to 201,397 acres

The Associated Press reported in October that Trump called Sen. Orrin Hatch, R-Utah, to say he would be shrinking the monuments.

“I’m approving the Bears Ears and Grand Staircase recommendation for you, Orrin,” Trump told Hatch.

What power do presidents have over national monuments?

The Antiquities Act, which was signed into law in 1906 by President Theodore Roosevelt, gives the president authority to designate federal land as a national monument “to protect landmarks, structures, and objects of historic or scientific interest.”

The law also makes it a crime to remove or destroy artifacts or damage archaeological sites on the federally protected land.

In the last two decades, 51 national monuments have been declared by Presidents Bill Clinton, George W. Bush and Barack Obama.

The newest such national monument is Bears Ears in southeastern Utah. President Obama established the more than 1.35 million acre monument on Dec. 28, 2016. Native American tribes say the land hosts some of the oldest and most sacred archaeological sites in Utah, and often perform ceremonies there. Bears Ears is also home to red rock canyons and dinosaur fossils.

The Grand Staircase-Escalante national monument, created in 1996 by President Clinton, is the largest national monument in the United States. It spans nearly 1.9 million acres, with canyons, natural bridges and monoliths. Geologists and archaeologists come to Grand Staircase-Escalante for excavations, many of which have revealed geological information dating back to dinosaur era.

Trump said Monday in Utah that his predecessors had “violated the spirit” of the act, and that previous administrations had ignored standards about how much land should be restricted.

Why is this so controversial?

Ranchers and landowners in the West, along with Republican lawmakers, oppose what they see as federal overreach on public land, with unnecessary restrictions on extracting natural resources from the land.

Native American groups have spoken out against protection reductions for land they view as sacred. Some tribes, along with conservationists, have also decried the reduction as illegal. The five tribes who make up the Bears Ears Inter-Tribal Coalition are planning to file a joint suit over Trump’s decision when it is announced, for “violating the Constitution’s separation of powers.”

“I don’t think it is controversial, actually — I think it’s sensible,” Trump said during his speech Monday.

PBS NewsHour will update this story as it develops