All forests are important, but some play larger roles than others. And for a few reasons, the Tongass National Forest in Southeast Alaska — known as the "crown jewel" of U.S. national forests — casts an especially long shadow.

Here's a closer look at the Tongass, why it's so important and why you might be hearing more about it in the near future:

It's big.

The Tongass National Forest is ancient and enormous, spanning nearly 17 million acres (69,000 square kilometers) of Southeast Alaska. For context, that's roughly the same total area occupied by the entire state of West Virginia. The Tongass is also big enough to hold two Belgiums, three New Jerseys or 17 Rhode Islands, and it's more than 20 times the size of Yosemite National Park. Established by President Theodore Roosevelt in 1907, the Tongass is the largest of 154 national forests across the country.

It's no ordinary forest.

The Mendenhall Glacier is a river of ice that stretches for 13 miles (21 km) through the Tongass National Forest. Dee Browning/Shutterstock

Size matters for any forest, since a big, unbroken woodland can generally support more wildlife and provide more ecosystem services to people, both near and far. But while the sheer scale of the Tongass is impressive, that's only part of its appeal.

The Tongass includes the largest temperate rainforest left in North America, and holds nearly a third of all the old-growth temperate rainforest left on Earth. Together with British Columbia's Great Bear Rainforest, just across the Canadian border to the south, it forms the largest intact temperate rainforest on Earth, according to Audubon Alaska.

Along with its vast woods, the Tongass features up to 17,000 miles (27,000 km) of pristine creeks, rivers and lakes, including important salmon-spawning streams. It also has wetlands, alpine tundra, mountains, fjords and 128 glaciers, and there are 19 designated wilderness areas located within its borders, more than any other national forest.

It's teeming with life.

A black bear and bald eagle share a tree at Anan Creek Wildlife Observatory in the Tongass National Forest. U.S. Forest Service Alaska Region [CC BY 2.0]/Flickr

This type of ecosystem is not only rare, but also highly valuable to wildlife. "Old-growth temperate rainforests hold more biomass (living stuff) per acre than any other type of ecosystem on the planet, including tropical jungles," explains the Southeast Alaska Conservation Council. The Tongass hosts deep forests of old-growth cedar, spruce and hemlock trees, some of which are more than 1,000 years old, as well as blueberries, skunk cabbages, ferns, mosses and many other plants in its understory.

It's home to a wide range of native animals, too, including all five species of Pacific salmon, steelhead trout, brown bears, black bears, gray wolves, Sitka black-tailed deer, mountain goats, flying squirrels, river otters, humpback whales, orcas, bald eagles, northern goshawks and marbled murrelets, to name a few.

People live there, too.

The city of Ketchikan, located within the Tongass National Forest, depends heavily on tourism and commercial fishing. MollieGPhoto/Shutterstock

The Tongass, and Southeast Alaska overall, has been continuously inhabited by Alaska Native people for thousands of years, including the Tlingit, Haida and Tsimshian. The forest itself is named after the Tongass group of Tlingit people, who lived in the southernmost areas of Southeast Alaska, near what's now the city of Ketchikan.

About 70,000 people live in the Tongass today, according to the Alaska Wilderness League. Nearly half of those are in the state capital of Juneau, which is located within the Tongass, but this population is spread among 32 different communities.

It sequesters a lot of carbon.

The Tongass may hold nearly a tenth of all carbon sequestered in U.S. national forests. Lee Prince/Shutterstock

Thanks to its wealth of biomass, especially all those old-growth trees, the Tongass also benefits humans and wildlife around the world by absorbing and sequestering large amounts of carbon dioxide from the atmosphere. It retains more atmospheric carbon than any other forest in the U.S., as Jessica Applegate and Paul Koberstein reported last year in Sierra Magazine, adding that "few forests on the planet play a greater role than the Tongass in helping to mitigate climate change."

The Tongass alone holds about 8% of all carbon stored in national forests across the country, the Southeast Alaska Conservation Council notes, and is recognized as a "globally significant carbon-storage reserve."

It's currently at a crossroads.

A rainbow reflects in the water at Kootznoowoo Wilderness, part of the Tongass National Forest. Don MacDougall [public domain]/Forest Service/Flickr

Despite its enormity, this forest used to be even bigger. As the Southeast Alaska Conservation Council puts it, the Tongass is "the still-thumping heart of a rainforest that once stretched uninterrupted from Northern California through Oregon, Washington, British Columbia and Alaska." And while it may still be huge and healthy, conservationists worry about the toll industrial logging has taken on the Tongass over the years — and the toll it could still take in years to come.

Past logging has already altered the Tongass, especially old-growth forest stands with the biggest trees. Only about 9% of the Tongass' productive old-growth forest has been cut so far, according to Audubon Alaska, but "perhaps half of the big-tree old growth has been cut." These are also the most important areas for wildlife and for ecological integrity.

This old growth has been more protected in recent years, thanks to a 2001 regulation known as the Roadless Rule, which bans new roads on more than 58 million acres of national forests that are already road-free, according to the Sierra Club, including about 22 million acres in Alaska. Now, however, the Trump administration has proposed exempting the Tongass from this rule, declaring its preference for a plan that would "remove all 9.2 million acres of inventoried roadless acres and would convert 165,000 old-growth acres and 20,000 young-growth acres previously identified as unsuitable timber lands to suitable timber lands."

Although some state and federal officials see economic opportunity in nixing protections for the Tongass, the idea worries conservationists and tribal governments in Alaska, NPR reports. Enacting this proposal could not only unravel ecosystems and worsen climate change, they argue, but it would also needlessly risk the region's tourism industry. The timber industry now accounts for less than 1% of the jobs in Southeast Alaska, the Sierra Club reports, while some 10,000 people in the region work in tourism. Those businesses generate about $2 billion per year for the local economy and draw about 1.2 million annual visitors — people who "don't come for vistas of logged forests," the group adds.

Sunlight filters through Tongass National Forest in Alaska. (Photo: CSNafzger/Shutterstock)

Plus, as many critics of the idea point out, the logging that does occur in the Tongass has not been a great investment for U.S. taxpayers. Federal subsidies for Tongass timber harvests total about $20 million per year, according to the Southeast Alaska Conservation Council, which translates to roughly $130,000 per timber job. Since 1982, taxpayers have lost about $1 billion from Tongass timber sales, according to the National Audubon Society.

If the Tongass is exempted from the roadless rule, the environmental effects could be "horrifying" and "far worse than you can imagine," science writer Matt Simon reports in Wired, explaining how new roads and logging could trigger domino effects that tear apart the forest's ancient ecological relationships. Yet at the same time, given the scope of habitat loss around the world, we're lucky we still have a place like this to save. As Audubon Alaska puts it, "the Tongass National Forest provides us with the greatest opportunity in the nation, if not the world, for protecting temperate rainforest at the ecosystem scale."

The U.S. Forest Service will hold a series of public meetings about its Tongass proposal, with locations to be posted on the Alaska Roadless Rule project website. Members of the public can also submit online comments about the proposal, until Dec. 17 at midnight Alaska time. A final decision is expected by June 2020, according to the Forest Service.