US President Donald Trump has slashed the size of two Utah conservation areas, the first such large-scale reversal in more than 100 years.
Mr Trump made the announcement following a review by the Interior Department after he ordered the agency in April to identify which of 27 monuments designated by past presidents should be rescinded or resized to give states and local governments more control of the land.
"Some people think that the natural resources of Utah should be controlled by a small handful of very distant bureaucrats located in Washington.
"And guess what? They're wrong," Mr Trump said alongside Utah's Republican governor, Gary Herbert, the Utah congressional delegation and local county commissioners.
Unlike national parks that can only be created by an act of Congress, national monuments can be designated unilaterally by presidents under the century-old Antiquities Act, a law meant to protect sacred sites, artifacts and historical objects.
"The families and communities of Utah know and love this land the best, and you know the best how to take care of your land," Mr Trump said.
Your timeless bond with the outdoors should not be replaced with the whims of regulators thousands and thousands of miles away
Mr Trump signed two proclamations after his speech in Salt Lake City.
One would reduce the 1.3 million acre Bears Ears National Monument, created in 2016 by then president Barack Obama in southeastern Utah, by more than 80% split into two areas.
The other would cut the states 1.9m acre Grand Staircase-Escalante National Monument, designated by former president Bill Clinton in 1996, nearly in half.
The landscape of canyons, ridges and rock formations would be split into three zones.
The move could open the door to energy exploration and other commercial use.
While a handful of monuments have been resized in the past, none has been cut back to such an extent, putting the president's proclamation in uncharted legal territory.
Previous presidents, including Woodrow Wilson and William Howard Taft, reduced some monuments but were never challenged in court.
"Here, and in other affected states, we have seen harmful and unnecessary restrictions on hunting, ranching and responsible economic development," Mr Trump said.
"We have seen grazing restrictions prevent ranching families from passing their businesses and beloved heritage on to the children."
Grazing and hunting were already permitted in both the Bears Ears and Grand Staircase monuments
The results of the Interior Department's broader review of US national monuments will be published today and is expected to outline changes to a number of other sites.
Mr Trump's opponents say the areas are home to more than 100,000 archaeological sites, including rock art that is at least 5,000 years old and the remains of 21 previously unknown dinosaur species.
The move raises questions about the durability of other conservation areas designated under the 1906 Antiquities Act.
"This law requires that only the smallest necessary area be set aside for special protection as national monuments," Mr Trump said.
"Unfortunately, previous administrations have ignored the standard and used the law to lock up hundreds of millions of acres of land and water under strict government control."
Mr Trump said these two areas were a different order of magnitude.
"I understood how big it is - I'm a real estate developer. When they start talking about millions of acres, I say, 'say it again? That's a lot,'" Mr Trump remarked.
Environmental lobby group Friends of the Earth accused Mr Trump and his allies of plundering resources.
"Donald Trump is overseeing the largest elimination of protected areas in US history.
"Dismantling these monuments is Trump's latest gift to the corporate interests who backed his campaign. This action is unprecedented and will end up in court," the group said in a statement.
Ten environmental protection groups, including the Sierra Club and The Wilderness Society, have filed a lawsuit against the Trump administration.
The lawsuit denounced the "unlawful proclamation" which it said "flouted 111 years of conservation history" and would leave natural "treasures exposed to immediate and ongoing harm."
"This is a sad day for indigenous people and for America," Navajo Nation Vice President Jonathan Nez said in a statement, adding the Native American tribe would also file a lawsuit against the Trump administration along with four other tribes.
