The federal government plans to offer nearly 156,000 acres of public land in Colorado in an upcoming lease sale, including habitat for the nation’s largest elk herd.

The June 16 lease sale by the Bureau of Land Management includes migration corridors for elk, pronghorn and mule deer migration corridors, with about two-thirds of the acreage in northwestern Colorado just south of Dinosaur National Monument, according to Capital & Main.

Conservation organization Rocky Mountain Wild called it the “largest oil and gas sale ever proposed in Colorado that we know of.”

Local tourism officials in Moffat County, where elk hunting is a major source of revenue, have spoken out against the sale. Dinosaur National Monument is one over 40 certified areas in the U.S. with an International Dark Skies designation, which they say could be threatened by lights and truck traffic from the oil and gas industry.

“Things like that could put that status in jeopardy,” said Tom Kleinschnitz, Moffat County’s director of tourism, told Capital & Main. “In the long run, I think it’s important to keep these areas as pristine as possible.”