The Trump administration is pursuing a major rollback of federal land protections — prompting a furious response. Here's everything you need to know:

What's at stake?
The fate of millions of acres of federal land. Last month, President Trump slashed the size of two national monuments in Utah by 2 million acres — reversing, he said, a "massive federal land grab" by former Presidents Clinton and Obama. The red rock canyon country of Bears Ears will shrink by 85 percent; Grand Staircase–Escalante, meanwhile, will be halved. These reductions came after a major lobbying campaign by the uranium industry. In addition to the Utah monuments, Interior Secretary Ryan Zinke has recommended that Trump shrink or modify another eight national monuments created since 1996 — stretching from the Atlantic Ocean to California's fir forests. These decisions have sparked a fierce battle between those who believe local residents and the free market should decide whether federal lands in a given state are developed and conservationists who believe the nation's remaining wilderness areas belong to the American public. "The Trump administration is walking into a legal, political, and moral minefield," says Kate Kelly, public lands director for the Center for American Progress.

How are monuments created?
Unlike national parks, which can only be designated by Congress, national monuments are established with the stroke of a presidential pen. Under the century-old Antiquities Act, presidents have the authority to preserve landmarks and "other objects of historic or scientific interest" that are already under federal control, so long as they limit them to the "smallest area compatible with proper care and management." Originally designed to protect against the looting of ancient artifacts, the act has since been used by 16 presidents, both Republican and Democratic. But conservatives say Clinton and Obama abused the act far beyond its intended purpose — creating "mega-monuments" that have locked up huge swaths of the West from traditional land uses, such as hunting and grazing. Obama protected 553 million acres during his presidency. His 29th monument, Bears Ears, was established shortly before he left office — causing an uproar in San Juan County.

Why is that?
Many Utahans saw Obama's move as a "betrayal." San Juan is one of the poorest counties in Utah, a state where more than 60 percent of the land is controlled by Washington. Residents already have to deal with a long list of federal restrictions, and many felt the Obama administration was depriving them of their livelihoods and much-needed revenue by closing off another 1.35 million acres — an area the size of Delaware — of oil, gas, and uranium-rich land. "The Antiquities Act is supposed to protect specific objects," says San Juan County Commissioner Phil Lyman, "not millions of acres."

What do conservationists say?
They argue that tourism and outdoor recreation bring more money into a community than traditional uses of the land. A study of 17 national monuments by independent nonprofit Headwaters Economics found that every local economy expanded in every single case after the monument was established. Unlike mining and fossil fuel drilling, Trump's critics add, tourism preserves America's natural heritage for future generations. Native American activists contend that his Bears Ears decision alone threatens some 100,000 sites of archaeological importance, including gravesites and ancient cliff dwellings, while uranium mining also threatens drinking water. "It's a historical trauma our people have been through over and over," Helaman Thor Hale, a local Native American, told The New York Times.

Will they fight the decision?
A number of advocacy groups have already filed legal challenges, and if Trump targets monuments outside of Utah, the fight will expand and intensify. Rural parts of Utah, Nevada, and Idaho are currently a hotbed of "resistance" to federal control. That resistance exploded in 2014, when Nevada-based cattle rancher Cliven Bundy led an armed standoff with law enforcement over unpaid federal grazing fees, and continued two years later when his son seized the headquarters of the Malheur National Wildlife Refuge in Oregon. But Trump's rollback faces a much chillier reception in the West's blue states. California's attorney general has already vowed to launch a legal challenge if Trump touches the state's national monuments — arguing the president doesn't have the authority to do so.

What does the law say?
That has yet to be decided by the courts. Some legal experts say the wording of the Antiquities Act makes it a "one-way ratchet" — only directly authorizing presidents to create monuments, not reduce or abolish them. But in practice previous presidents have shrunk national monuments 18 times — including during World War I, when Woodrow Wilson halved the size of Mount Olympus National Monument to provide timber for Navy ships. In 1963, President John F. Kennedy slightly downsized Bandelier National Monument in New Mexico. No one legally challenged those decisions, however. Trump's attempted rollback will force courts to settle the dispute over the Antiquities Act's wording, says law professor James Rasband. "A new chapter in the meaning of the act may be about to be written," he says.

From Devils Tower to Mount Rushmore
In 1906, Theodore Roosevelt declared the first national monument: Devils Tower, a 1,267-foot piece of igneous rock jutting out of Wyo­ming's prairie. Today, more than 151 national monuments dot the ­country — ranging from Hawaii's Papahanaumo­kua­kea, which sprawls for hundreds of thousands of square miles under the Pacific Ocean, to Aztec Ruins in New Mex­ico. Some, like the Grand Canyon, have gone on to become national parks. Like Obama, Pres­i­dent Jimmy Carter incensed many by aggressively utilizing the Antiquities Act. The 39th president created 17 monuments covering 56 million acres of wilderness in ­Alaska — earning himself the honor of being burned in effigy by Alaskans, who relied on the local oil industry for jobs. Even as the Trump administration dramatically reduces some existing monuments, it has proposed three new national monuments to add to the list, including a 130,000-acre region in Montana adjacent to the Blackfeet Indian Reservation and Glacier National Park. Interior Secretary Ryan Zinke says that the administration sees development of federal lands as a means to establish "energy dominance," but that not all such lands are appropriate for that use.