They shrink. They grow. The tricky politics of national monuments.

The Explainer

For more than a century, presidents have created national monuments to protect areas of historic, scientific, or cultural significance. But in December 2017, to expand fishing and mining rights, Republican President Donald Trump cut the size of Bears Ears National Monument and two other national monuments: Grand Staircase-Escalante in southern Utah and Northeast Canyons and Seamounts Marine off Cape Cod.

The move raised a key question: If a president can designate a national monument, can a different president take it away?

Public land protections “must not become ... a pendulum that swings back and forth depending on who’s in public office,” said President Joe Biden in a speech this fall after restoring the original boundaries for the three monuments, originally established by Democratic Presidents Bill Clinton and Barack Obama.

But the designation of national monuments in the United States is more than partisan tug of war. Underneath the administrative back and forth lie questions about executive power, stewardship, and trust.

How are national monuments created?

Unlike a national park, which is created through an act of Congress, national monuments can be created by the president alone through the Antiquities Act of 1906.

When the act was first established, people were concerned about the “looting and destruction of archaeological sites that was occurring,” says Frank Pierce-McManamon, founding director of the Center for Digital Antiquity at Arizona State University. Presidential power meant faster protection.

The act’s passage was bolstered by a shift in national thinking about the value of nature as more than a resource for extraction.

As the nation developed and urbanized, “the open spaces began to have a perceived greater value ... not just in board feet of timber ... but an aesthetic value that spoke to the need for open spaces,” says Sara Dant, author of “Losing Eden: An Environmental History of the American West.”

When did national monument designations become controversial?

Since the early 20th century, more than 100 national monuments have been created by both Republican and Democratic presidents. But “there have been questions surrounding the act, particularly the size of national monuments ... pretty much from the beginning,” says Dr. Pierce-McManamon.

National monuments are created on land owned and managed by the federal government. A national monument designation changes what is allowed on the land. Often, activities such as drilling, mining, and grazing are prohibited, but existing land rights are grandfathered in.

The use of the Antiquities Act so far in the 21st century has reignited old debates about how public land should be used: whether for natural resource extraction or for the preservation of diverse ecosystems, carbon-sequestering soils, and areas sacred to Native American tribes like Bears Ears.

The public lands debate is about not just land use but whether the president and the federal government at large are the appropriate caretakers.

“The lands are overseen by bureaucrats thousands of miles away in Washington, and the very people whose lives are most affected ... are denied any say in the process,” wrote members of Utah’s congressional delegation in an opinion piece after Mr. Biden reinstated the monuments’ original boundaries.

While some Americans trust that “the federal government has a positive stewardship role to play,” others “are more wary and less confident of a federal government that will do good for all the citizens,” says Dr. Dant.

What’s next?

Lawsuits arguing that Mr. Trump’s reversal was an unconstitutional expansion of executive power are still pending, and resolution will require either a court ruling or an update to the Antiquities Act by Congress.

The current ambiguity poses practical challenges, says Dr. Pierce-McManamon. When boundaries change every four years, it becomes difficult to manage the land effectively over the long haul.

Long-term resolution concerning how public lands should be used and who has the power to decide requires moving away from a zero-sum mentality, says Dr. Dant. “Finding that balance between the national and the local ... and caring then about these places that we all share, I think that’s really key.”