Two environmental groups said Tuesday they will sue the federal government for trading away thousands of acres of habitat critical to wolves and lynx in northeastern Minnesota so that a copper-nickel mine might be built on the site.

It is the first of what could be multiple legal actions designed to stop a highly controversial open pit mine proposed by PolyMet Mining Corp. for a site near Hoyt Lakes on Minnesota’s Iron Range.

The Center for Biological Diversity and Earthworks issued the legally required notice that it will file a federal lawsuit in 60 days against the U.S. Forest Service and the U.S. Fish and Wildlife Service under the Endangered Species Act. On Monday, the Forest Service agreed to a land swap giving PolyMet 6,650 acres required for access to minerals it owns beneath the surface for its proposed mine. In exchange, PolyMet gave the Forest Service 6,690 acres of what are now privately held parcels scattered across northeast Minnesota.

“The Forest Service is trying to wash its hands of this terrible project through a land exchange with PolyMet, but the impacts on wolves and lynx are just too severe to allow this to proceed,” said Marc Fink, an attorney with the center.

The federal agencies did not immediately respond to a request for comment.

“We believe the [opinion] issued by the Fish and Wildlife Service fully addresses the potential impacts,” said Bruce Richardson, vice president of communications for PolyMet.

Wolves and lynx both are listed as threatened under the Endangered Species Act, which requires federal agencies to ensure protection of critical habitat. Last year the Wildlife Service found that the PolyMet land exchange would not result in significant harm to either species.

But the environmental groups say the project would destroy 4,000 acres of forest and wetlands used by both predators. Despite this admission, the environmental groups said, the agency arbitrarily determined that this large-scale, permanent habitat destruction would somehow not “adversely modify” the critical habitat.

Minnesota has about 2,300 wolves — the largest population in the Lower 48 states — and about 200 lynx.