The Biden administration has withdrawn some 225,000 acres of national forest land in northern Minnesota from mineral leasing, protecting a swath of the watershed that adjoins the Boundary Waters Canoe Area Wilderness.

The decision follows a 16-month review on whether the minerals lying under Superior National Forest should be open to extraction. The Department of Interior concluded the land should be protected for 20 years, the maximum possible without congressional approval.

In a study released in 2022, the U.S. Forest Service concluded that hard-rock mining on the land risked contaminating the Boundary Waters, even with mitigation measures in place.

Superior National Forest is part of the Rainy River watershed, which flows into the Boundary Waters. It is also part of land ceded in an 1854 treaty by Ojibwe tribes in Minnesota, and members of these bands retained rights to hunt, fish and gather on these lands.

"Protecting a place like Boundary Waters is key to supporting the health of the watershed and its surrounding wildlife, upholding our Tribal trust and treaty responsibilities, and boosting the local recreation economy," Interior Secretary Deb Haaland said in a statement Thursday.

It's the second big move in federal land protection this week. On Wednesday, the Biden administration said it would not allow roads or logging on some 9 million acres of temperate rainforest in Alaska's nearly 17 million-acre Tongass National Forest.

There are no active mineral leases on the Minnesota land that was withdrawn from mining, but the long-planned Twin Metals mine was slated for the area, near Ely. Twin Metals, a subsidiary of Chilean mining giant Antofagasta, lost its mineral leases when the Biden administration canceled them at the beginning of 2022. The company sued the federal government later in the year to have them restored. The suit is pending in federal court.

Kathy Graul, a spokeswoman for Twin Metals, wrote in an email that the company was "deeply disappointed and stunned" by the new moratorium.

"This region sits on top of one of the world's largest deposits of critical minerals that are vital in meeting our nation's goals to transition to a clean energy future, to create American jobs, to strengthen our national security and to bolster domestic supply chains," Graul wrote. "We believe our project plays a critical role in addressing all of these priorities, and we remain committed to enforcing Twin Metals' rights."

Another company, Encampment Minerals, was also conducting exploratory drilling on the land that's part of the moratorium. A representative for the company declined to comment.

Conservation groups have long argued that mining for copper, nickel and other metals could spoil the natural beauty and health of the Boundary Waters, more than 1 million acres of the country's most-visited federal wilderness. While Minnesota has a long history of iron mining, hard-rock mining for other metals would be new to the state and brings the risk of environmental damage from acid mine drainage.

"This is the most important land conservation victory for the Boundary Waters in 45 years," said Becky Rom, national chair of the Campaign to Save the Boundary Waters. She noted that 45 years ago, Congress banned mining within the wilderness itself.

"You don't let the most polluting industry in America operate next to a pristine wilderness that contains an abundant supply of the cleanest water in the country. This is common sense," Chris Knopf, executive director of Friends of the Boundary Waters Wilderness, said in a statement.

Others have hoped a new wave of mines, spurred in part by increasing demand for metals for electric vehicle batteries, could bring jobs to northeastern Minnesota.

"This action begs the question: Why doesn't the government have confidence in its own agencies' ability to review proposed specific projects?" asked David Chura, chair of the business group Jobs for Minnesotans.

In a statement, Republican U.S. Rep. Pete Stauber, whose district covers the area where mining is now stopped, called the decision "an attack on our way of life."

"I can assure you that this Administration, from the President to the Forest Service, to the Interior Department, will answer for the pain they elected to cause my constituents today," Stauber said.

The decision could be reversed by a future presidential administration. Democratic U.S. Rep. Betty McCollum previously introduced a bill to permanently protect a slightly larger area in Superior National Forest from hard-rock mining. McCollum said in a statement Thursday that she would reintroduce the bill. However, it would face an uphill path in the now GOP-controlled House of Representatives.

McCollum, whose district covers St. Paul and other parts of the east metro, wrote that she would "continue working to protect this national treasure in perpetuity."

Two other major mining projects in northeastern Minnesota, the PolyMet mine near Hoyt Lakes and a Talon Metals mine in Tamarack, are not affected by the federal moratorium. PolyMet is being held up by multiple legal challenges, and Talon has not yet submitted its mining plan and started environmental review.