SALT LAKE CITY – The U.S. Fish & Wildlife Service is on a collision course with another federal agency by proposing to list more than 100 square miles in northeastern Utah and northwestern Colorado as critical habitat for a pair of desert wildflowers, threatening oil production in an energy-rich area.

The U.S. Bureau of Land Management has authorized the same public lands for development of oil shale, a greasy rock that contains fossilized algae. Petroleum companies are trying to extract this primitive form of oil.

The two plants, Graham’s beardtongue and the White River beardtongue, thrive on oil-shale outcrops, which are rich in calcium carbonate, a plant nutrient.

A listing of critical habitat would require BLM to consult government biologists before issuing permits for oil-shale works, said Bekee Hotze, a branch chief in Utah for the Fish & Wildlife Service.

“There are definitely conflicts with plants and oil-shale development,” Hotze said Tuesday.

“We’re working with people to find out ways we can do both,” he said.

The Fish & Wildlife Service announced its proposed listing Monday in the Federal Register. Officials said the plants already are suffering from conventional oil and gas development, livestock grazing, invasive weeds and climate change.

For Graham’s beardtongue, the agency wants to designate a section of land 80 miles long and six miles wide as critical habitat for an estimated 6,200 plants – right through the heart of oil-shale country.

That band extends from an edge of Duchesne County in Utah to a sliver of Rio Blanco County in Colorado. At 106 square miles in size, it encompasses five designated habitat zones.

Overlapping that area are 23 square miles of zones the agency wants designated for White River beardtongue. Much of that land borders Utah and Colorado. The Fish & Wildlife Service believes the three zones hold about 11,400 plants.