A nonprofit conservation group is launching what it says is one of the largest lawsuits ever brought under the Endangered Species Act.

The Center for Biological Diversity intends to sue the Trump administration for failing to tackle a backlog of hundreds of species waiting for a decision on federal protection. They include wolverines, whitebark pine and western bumble bees — all endemic to the Mountain West.

“If we just leave them in the bureaucratic purgatory, we’re not accomplishing anything. We’re just allowing them to decline further making recovery more expensive, less likely, and more difficult,” said Noah Greenwald, endangered species coordinator for the Center for Biological Diversity.

The U.S. Fish and Wildlife Service has an ongoing work plan to address a backlog of more than 250 species over the next few years. But Greenwald argues the Trump administration has kept the agency from tackling the backlog.

FWS, for example, is still mulling whether to list the wolverine as a threatened species. It last took action on the animal in 2016, when it reopened a public comment period on a proposed rule to list the species. That came after a federal court in Montana overturned the agency’s decision to withdraw its 2014 proposal to list the snow-dependent wolverine.

“So far the Trump administration has only protected 21 species under the Endangered Species Act, which is the lowest level for any administration at this point,” he said. “We feel like we have no assurances that these species are going to get the life-saving protections they need.”

FWS is required by law to make recommendations on federal protections within one year, or else give good reason for the delay.

In a statement, the agency argued that it has already made decisions on a number of species listed in the work plan, though it could not give a specific number.

“[The Center for Biological Diversity’s] notice of intent grossly mischaracterizes the volume of our outstanding Endangered Species Act actions,” a spokesperson said. “A lawsuit will only serve to divert more of our limited resources towards litigation and away from the important work of conserving our nation’s wild life.”

In a letter to the agency, the Center of Biological Diversity said the agency has 60 days to either release its findings on species awaiting a listing determination or create a legally binding timeline to do so. If that doesn’t happen, the environmental organization will file suit.

This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Boise State Public Radio in Idaho, KUER in Salt Lake City, KUNR in Nevada, the O’Connor Center For the Rocky Mountain West in Montana, and KRCC and KUNC in Colorado.