The Biden administration announced sweeping protections for Alaska’s Tongass National Forest on Thursday, including an end to large-scale old-growth logging and a proposal to bar road development on more than 9 million acres.

The changes mark a major shift for a region that has relied on felling massive trees for more than a century, reversing one of former president Donald Trump’s biggest public land decisions and halting a significant source of future carbon emissions. The Tongass, part of one of the world’s last relatively intact temperate rainforests, is the only national forest where old-growth logging still takes place on an industrial scale.

The 16.7 million-acre forest — which once boasted major pulp mills but is now targeted for its fine-grain, centuries-old trees that are coveted for pricey musical instruments, expansive outdoor decks and elegant shingles — has been a political flash point for two decades. While Democrats have sought to scale back logging in the forest over time, the administration’s moves go further than any previous president’s efforts.

Agriculture Secretary Tom Vilsack said the proposal would provide $25 million for community development and would allow Alaska Natives and small-scale operators to continue to harvest some old-growth trees. But Vilsack — who proposed a much more gradual transition away from old-growth logging when he was secretary under President Barack Obama — said it’s time to focus on other economic activities, such as fishing, recreation and tourism.

“This approach will help us chart the path to long-term economic opportunities that are sustainable and reflect southeast Alaska’s rich cultural heritage and magnificent natural resources,” he said.

Although timber operations felled large swaths of its largest trees between the 1960s and the 1980s, about 5 million acres of prime old-growth habitat remain, according to the Forest Service.

There were plans for three major old-growth harvests of more than 15,750 acres on Forest Service land, on Prince of Wales Island and Revillagigedo Island, as well as one that encompasses Mitkof, Kupreanof, Kuiu, Wrangell, Zarembo and Etolin islands and the U.S. mainland. Since the environmental analyses were not complete and final decisions had not been made, administration officials said, these sales would not take place.

The agency will offer limited sales of old growth for community and cultural uses, such as totem poles, canoes and weaving, which would probably allow the region’s smaller mills to keep operating.

Scientists have identified logging in Tongass as a future driver of planetary warming, because its ancient trees — many of which are at least three centuries old — absorb at least 8 percent of the carbon stored in the entire Lower 48 states’ forests combined.

“This is the most important thing that can happen in terms of preserving forests,” Beverly Law, a professor emeritus of global change biology at Oregon State University, said in a phone interview.

She noted that the carbon stored in old-growth trees can stay out of the atmosphere for about 1,000 years if they remain uncut, while research has found that about 65 percent of the carbon held by trees that are felled is released in the ensuing decades. “It’s becoming obvious to people who aren’t aware that our forests are the most effective way of taking up carbon and storing carbon for much longer than anywhere else.”

Alaska’s statewide elected leaders, including Gov. Mike Dunleavy, Sens. Lisa Murkowski and Dan Sullivan, and Rep. Don Young, all Republicans, have consistently opposed restrictions on logging and other forms of industrial development within the forest. In October, Trump exempted the state from the Roadless Area Conservation Rule, which President Bill Clinton enacted in 2001.

Dunleavy said in a statement that the Forest Service had already concluded that exempting the state from the roadless rule “was fully justified.”

“Narrow election results and political donations from environmental groups do not justify this federal agency’s policy flip-flop,” he said. “Our state’s southeast communities need fundamental access, like roads, and the economic and resource development opportunities roads provide. Every Alaskan deserves the chance to work. We have the resources. We just need the opportunity.”

Some local officials have also pressed to build more roads to extract other resources, such as gold and rare-earth metals.

Tim O’Connor, mayor of the town of Craig on Prince of Wales Island, said in an email that curbing development would undercut the local tax base.

“If we don’t have access to the road systems due to the roadless rule, it affects our ability to hunt food and resources for subsistence,” he said. “Also we will not be able to develop mines, hydro projects and minerals needed by our country for strategic needs.”

But a broad coalition of Alaska Native leaders, environmentalists, commercial fishing operators, anglers and tourism companies have argued that protecting southeast Alaska’s rugged terrain represents the best way forward. Much of the Tongass is accessible only by boat, small plane or on foot. Towering stands of Sitka spruce, western hemlock, red cedar and Alaska yellow cedar blanket much of the archipelago, and safeguard waterways teeming with five species of wild salmon.

Millie Schoonover, 74, is a member of both the Craig Tribal and the Craig City councils and said in an interview that she has seen the area transformed over the course of her lifetime. “Logging was a good thing, but it’s way out of balance,” she said.

To manage the forest properly, she said, policymakers need to safeguard the salmon, deer and other game people have caught and hunted for centuries. “We don’t overharvest everything.”

Joel Jackson, president of the Organized Village of Kake, has spent two decades fighting to preserve the forest’s roadless areas. He said in a phone interview that he welcomes the cancellation of three major timber sales and the new grants.

“It’s a start,” he said, adding that the federal government had spent tens of millions of dollars a year subsidizing logging.

Austin Williams, Alaska director of law and policy for Trout Unlimited, said in an email that the Forest Service had decided to “align itself with the economic realities of the region, where fishing, guiding and tourism have been the mainstays for decades.”

“We need healthy rivers and forests, abundant fish and wildlife, beautiful scenery, and management that recognizes the cultural values of the forest, not more costly and damaging clear-cut logging of old-growth forest,” he said.

It is peak tourist season in southeast Alaska right now, and while large cruise-ship traffic has dipped because of the pandemic, smaller-scale tourism is booming. Alaska Seaplane Adventures General Manager Dan Kirkwood, who leads trips to watch brown bears hunting salmon and co-chairs a tourism business working group, said in an interview that the area remains a draw because it’s so undeveloped.

“When they say, ‘How do we create economic development in rural communities,’ this is what it looks like,” he said, adding that the new grants show the Forest Service is shifting from an agency focused on logging to one with a broader agenda.

“This is them saying, ‘We recognize we need to serve the diverse economies in southeast Alaska, and we’re recalibrating,’ ” Kirkwood said.

The Alaska Forest Association, however, questioned why the transition would be so abrupt. In a statement, it thanked Forest Service officials in Alaska for working to sustain old-growth timber sales while paving the way to harvest younger trees. “What a monumental loss for the USFS, the Tongass, and AK that this work will be set aside.”