Major American companies and conservationists are blasting President Donald Trump's decision to drastically reduce the reach of federally protected land at two national monuments in Utah.

Trump formally decided to reduce Bears Ears by about 85 percent and Grand-Staircase Escalante by nearly half in a trip to Salt Lake City on Monday. Collectively, the monuments house more than 100,000 Native American cultural sites and 20,000 archaeological sites. The decision – viewed as a win for Republican lawmakers, fossil fuel companies and rural Westerners and a loss for environmentalists, recreation groups and Native American nations – met with a mixture of criticism and praise online.

Patagonia, an outdoor clothing company, shared its stance in a clear message: "The President Stole Your Land." The company changed its website's landing page black to host its response, informing its consumers that the president reduced the protected lands in what it called "an illegal move." Patagonia CEO Rose Marcario said in a separate statement that the company would sue the Trump administration, according to AdAge.

"This is the largest elimination of protected land in American history," the company's website message continued. The page offers a button that allows users to "learn more" about the decision and to "take action now."

We just lost millions of acres of protected land. But we remain united as a community. Join us in solidarity by changing your profile pic to this photo. #UnitedOutside pic.twitter.com/czvyIgPgi6 — REI (@REI) December 4, 2017

If you’d like to support the creation of the Bears Ears Visit with Respect Center, you can take part of the kickstarter here: https://t.co/AvE7aqWzMy #MonumentsForAll pic.twitter.com/MMPNmlXqRm — The North Face (@thenorthface) December 4, 2017

Outdoor gear companies REI and The North Face joined in the protest. Each took to Twitter to urge consumers to stand against the president's announcement.

Trump on Monday proudly displayed his signed proclamation to applause from politicians and supporters gathered at the Utah State Capitol. The president's order to reduce the land comes in response to what Trump previously condemned as a "massive federal land grab" by the government. The president has claimed his predecessors overreached their authority to designate federally protected land under the Antiquities Act.

President Donald Trump holds up a signed proclamation to shrink the size of Bears Ears and Grand Staircase Escalante national monuments. (AP Photo/Rick Bowmer)

On Trump's order, U.S. Secretary of the Interior Ryan Zinke earlier this year conducted a four-month review to deliver recommendations on the status of 27 national monuments declared by former presidents Barack Obama and Bill Clinton.

Sen. Orrin Hatch, R–Utah, was among the politicians backing the changes to the monument, and celebrated Trump's visit on Twitter. Hatch said in a video posted to Twitter that he had spoken to people "most affected by the [Bears Ears] monument," who he said agreed that "there's a better way to balance priorities than just unilaterally locking up 1.5 million acres of land."

Still, the response against the presidential proclamation was loud and swift. Representatives from Native American tribes "vowed to unite and take the fight to court to preserve protections for lands they consider sacred," according to The Associated Press.

"It's just another slap in the face for a lot of us, a lot of our Native American brothers and sisters," said Navajo Nation Vice President Jonathan Nez, according to AP.