Two environmental groups are planning to sue over a trade that gives PolyMet the northeastern Minnesota land it needs for a possible copper-nickel mine.

On Monday, the U.S. Forest Service announced it agreed to trade about 6,650 acres of land it owns and manages on the southern edge of the Superior National Forest to PolyMet. In exchange, the Forest Service would get about 6,690 acres of land in the same area that PolyMet currently controls – that land would become part of the Superior National Forest.

PolyMet needs the land for the copper-nickel mine it hopes to operate near Hoyt Lakes. The open pit mine (meaning the top layer of earth would be removed) would tap into the Duluth Complex, which PolyMet calls one of the largest known undeveloped deposits of copper, nickel and other precious metals.

Groups concerned about the mine's affect on the environment immediately decried the land swap decision, which came after 22,000-plus public comments against it, as well as opposition from nearby Lake Superior Chippewa bands.

A lawsuit is coming

The Center for Biological Diversity, as well as the group Earthworks, announced they plan to file a lawsuit to stop the land swap. Specifically, the lawsuit says the mine would destroy the habitat of two threatened species – the gray wolf and the Canada lynx. If federal agencies allow that to happen (by swapping the land so a mine can be built), they're in violation of the Endangered Species Act, the groups argue.

The lawsuit itself hasn't been filed, but submitted a notice of intent – kind of like a 60-day heads-up a lawsuit is coming.

"The U.S. Forest Service just gave a foreign mining company part of our national forests to build a mine in one of the worst possible places for one — the headwaters of Lake Superior," Earthworks member Lori Andersen said in the announcement, adding the proposal would "destroy critical habitat" for the lynx and wolves.

The Canada lynx is a rare wildcat in Minnesota, the DNR says, and because of low population numbers has been protected in the state since 1984. It was classified threatened from the U.S. Fish and Wildlife Service in 2000.

Gray wolf numbers have gone up in recent decades after state and federal protections were put in place, the DNR says. There's an ongoing argument about whether they should be removed from the federally threatened species list because of that.

The mine still has multiple permits and approvals to get before it actually happens, plus potentially more legal hurdles such as lawsuits. So we're likely months and months away from knowing if it will become a reality.