Dolores River in Colorado is center of the latest public lands dispute

A 400,000-acre area along the Dolores River in southwestern Colorado is the newest battleground in the debate over public lands .

Why it matters: How the land is designated determines how the public can access and use it, whether for recreation or commercial purposes such as mining and livestock grazing.

State of play: A coalition of conservation and environmental groups wants President Biden to designate the river watershed that spans two counties as a national monument to increase land protections and limit development, the Colorado Sun reports.

• The advocates say the designation under the Antiquities Act is needed to preserve Indigenous cultural sites, geologic formations, paleontology sites, biodiversity and outdoor recreation opportunities.
• To bolster their point, supporters cite various polling that shows widespread support for conserving the land along the river that flows into the Colorado River and suggest it could open new economic opportunities, such as tourism.

What they're saying: "I think we have an opportunity to diversify our economy … and come up with a proposal that takes all of these uses into account so that everyone in these rural communities can prosper," Natalie Binder, a campground owner in Naturita, said at a recent community meeting.

The other side: Opponents consider the move a federal land grab and don't want the attention a national monument would bring to the region.

• In recent public forums, nearby residents expressed concerns about becoming like Moab, Utah, an outdoor recreation hot spot, and the potential limits on mining, development and other commercial uses. Montrose and Mesa counties formally oppose the monument proposal.
• "I think it absolutely, positively could be a threat," Sean Pond, a leading opponent, recently told the Sun . "If you look at the history of monument designations over time, more and more restrictions are put in place as more people start coming."

The latest: Mesa County commissioners put forward an alternative proposal this week that calls for a national conservation area to increase protections on just 30,000 acres along the river.

• The smaller area would limit additional federal protections on land important to mining, logging and grazing, they said.
• One organization behind the national monument proposal called Mesa County's pitch "grossly inadequate," the Sun reports.

Between the lines: Colorado's two U.S. senators, John Hickenlooper and Michael Bennet, are standing in the middle of the debate.

• The two Democrats introduced legislation to designate 68,000 acres of public lands as a conservation area, but stopped short of pushing for a national monument designation.

The bottom line: What happens with the legislation and the potential national monument designation will depend significantly on who wins the White House and Congress in the November election.

Editor's note: This story has been corrected to reflect that the proposed national monument would span two counties (not five).