Colorado’s Sen. Michael Bennet wants to know if  the U.S. Forest Service is asleep at the switch as the Trump administration aims to trim Bears Ears National Monument.

Bennet and Sen. Debbie Stabenow, a Democrat from Michigan, sent a letter Thursday to Agriculture Secretary Sonny Perdue, who oversees the Forest Service, asking pointed questions about how much of a fight the agency put up to defend its part of the southeast monument.

You can read the letter here.

The 1.35-million acre monument was designated by President Obama in December. In April President Trump asked for a review 27 national monuments of more than 100,000 acres each that were designated by previous presidents since Jan. 1, 1996. The review includes a pending decision on the Canyons of the Ancients near Cortez.

“Coloradans respect and value our public lands, because we understand that our public lands system is unique among all the countries in the world,” Bennet and fellow Colorado Sen. Cory Gardner said in a letter to Zinke last month. “Canyons is a significant piece of that uniqueness given the history that is preserved there.

Gov. John Hickenlooper got a personal assurance from Interior Secretary Ryan Zinke that the Canyons of the Ancients would be spared.

Monday Zinke said the size of Bears Ears, however, could be reduced, but he didn’t say by how much or where. Conservationists had worried about the elimination of the monument, which includes sacred American Indian historical sites.

“The area around Bears Ears has the highest density of archaeological sites. I don’t think there’s any dispute about that,” Zinke said, according to USA Today. “But if you look at the Bears Ears as a whole, there is a lot more drop-dead gorgeous land than there is historic landmarks and historic structures.”

The conservation-versus-commerce fight in Utah has been a national flashpoint in the public lands debate for years, but with a supportive Trump administration, the scales are tipped toward drilling and development.

Bennet points out in his letter than Bears Ears includes almost 300,000 acres of forested highlands in the Manti La-Sal National Forest.

He specifically presses the question of legal authority.

‘While the Antiquities Act authorizes the president to designate national monuments, there does not appear to be any authority within the act to reduce the size of the monuments,” Bennet’s letter states, signaling a fight he’s eager to have with the Trump administration.

Bennet is the ranking Democrat on the subcommittee on Conservation, Forestry and Natural Resources. Stabenow holds the same position in the Senate Committee on Agriculture, Nutrition and Forestry.

Scott Braden, the wilderness and public lands advocate for Conservation Colorado, the state’s largest environmental organization, called Zinke’s proposal a “slap in the face to all of us who care about and cherish our country’s national parks and monuments.”

He said Zinke is shortchanging cultural sites and public opinion to “attempt to appease Utah’s hard-right congressional delegation, a few county commissioners and Trump’s base.”

Braden said it is all too familiar a pattern for the federal government to go back on its word to native people.

“Coloradans should rid themselves of any harbored hopes that the President Trump or his loyal subordinates like Secretary Zinke will somehow be moderate on public lands issues,’ he said. “Their assault on public lands is real, and none of Colorado’s public lands are safe from it. Indeed, in Colorado, Trump has already attacked our Canyons of the Ancients National Monument, initiated a review of the collaborative greater sage grouse plan, and attempted to fast track a coal mine expansion into a roadless area. Colorado’s elected leaders must stand up to this malevolent administration.”