A new federal lawsuit contends that PolyMet Mining’s proposed open-pit copper and nickel mine in northern Minnesota threatens essential habitat for gray wolves and other wildlife. (Dreamstime/The Minnesota Star Tribune)

A new federal lawsuit over PolyMet Mining's proposed open-pit copper and nickel mine in northern Minnesota claims the project threatens essential habitat for gray wolves, Canada lynx and northern long-eared bats, and violates the federal Endangered Species Act.

The suit was filed Tuesday in federal court in Minneapolis by the Center for Biological Diversity, Save Lake Superior Association, Save Our Sky Blue Waters, Friends of the Cloquet Valley State Forest and Duluth for Clean Water.

Named as defendants were Interior Secretary Deb Haaland, and the U.S. Fish and Wildlife Service, the Forest Service and the Army Corps of Engineers.

The groups challenge the agencies' reliance on what they describe as a highly flawed wildlife assessment. The plaintiffs say the study — the Fish and Wildlife Service's Feb. 5, 2016, Biological Opinion for the NorthMet Mine Project and Land Exchange — and the decisions based on it violate the Endangered Species Act.

The Fish and Wildlife Service's "determination that the NorthMet Mine Project is not likely to jeopardize the Canada lynx, gray wolf, or northern long-eared bat, and is not likely to adversely modify the designated critical habitat for the Canada lynx or gray wolf, is unsupported, lacks any rational basis, is in disregard of the best available science, is contrary to the evidence, and is arbitrary and capricious," the lawsuit says.

The plaintiffs want, among other measures, to void the 2018 land exchange between the Forest Service and PolyMet, and halt mine development until the matter is resolved.

The Center for Biological Diversity said it challenged the Fish and Wildlife opinion when it was first issued, but the judge said the request was premature and dismissed it because not all the mine permits had been issued.

"I've challenged biological opinions for other mining projects, and they're much more extensive in their analysis," said Marc Fink, the center's Public Lands legal director.

The lawsuit is the latest challenge to the now-stalled $1 billion copper and nickel mine that PolyMet wants to build near Babbitt and Hoyt Lakes. PolyMet is majority owned by Swiss mining giant Glencore and based in St. Paul.

PolyMet spokesman Bruce Richardson said the company is reviewing the complaint, intends to participate and is "confident" in a positive outcome. He noted that a federal judge dismissed four other challenges to the land exchange in 2019.

Over much public opposition, the Forest Service conveyed 6,650 acres, or about 10 square miles, of federal land to PolyMet that the company needed for the mine. In exchange, the agency received 6,690 acres of nonfederal land in tracts around Superior National Forest.