6 Parks That Will Benefit Most from a New Rule on Old-Growth Forests

Few life moments are as humbling as standing next to an old-growth tree. If you’ve been fortunate to walk amid a forest of these giants, perhaps you’ve pondered all they’ve witnessed or reflected on your own smallness in their presence. Many of us have benefitted from old-growth forests — or from what remains of them after centuries of unrestrained logging.

NPCA’s Conservation Science team recently analyzed a data set of satellite imaging from the University of California, Berkeley to determine the amount of remaining mature and old-growth forests in the contiguous United States. Our major finding: The greatest concentration of these forests (35% of the total) is found on federal publicly owned lands — including 92 million acres managed by the U.S. Forest Service.

Roughly a quarter of this area (27 million acres) is within 30 miles of a national park. The same study found more than 3 million acres (3% of the total) of old-growth forests within national parks — and their health depends on the health of forests just outside of park boundaries.

Old-growth forests play a critical and often overlooked role in maintaining the health and vitality of our national parks — they sequester huge amounts of carbon, support wildlife, improve water quality and help protect larger ecosystems.

Earlier this year, the Forest Service announced a historic plan to better conserve and cultivate old-growth forests. This monumental proposal takes the first step in protecting old-growth forests by keeping the oldest trees standing rather than cutting them down.

The health of old-growth forests inside our national parks is connected to the health of forests just outside of park boundaries.

At the same time, we can’t just protect the oldest trees. We need to protect the large trees in the process of maturing into old growth, especially as our forests recover from historical logging practices. NPCA urges stronger protections — specifically, to allow trees characterized as “mature” to age into old-growth status.

Seventy-six national parks border national forests. Here are the top five parks identified by NPCA that have the most mature and old-growth forests in their broader landscapes. These parks — plus a bonus park! — stand to benefit the most if the U.S. Forest Service’s rule is approved.

1. Yellowstone National Park: Healthy wildlife

Forests cover about 80% of Yellowstone — the world’s first national park, which is located across sections of Wyoming, Montana and Idaho. Douglas fir is abundant, particularly in the northern region of the park. Some trees are estimated to be several hundred years old.

NPCA identified about 250,000 acres of old-growth forests within park boundaries, about 11% of the park, and another 753,210 within 30 miles of its border.

For the park’s iconic wildlife, healthy forests mean healthy food. Yellowstone’s diverse and abundant forests provide critical habitat and food sources for wildlife, ranging from the great horned owl and hundreds of other bird species to the endangered Canada lynx and Greater Yellowstone Ecosystem grizzly bear. Whitebark pine seeds, for example, are a critical food source for many grizzly bears, due to their high calorie content, and influence their health and reproduction.

But many whitebark pines have died across the Yellowstone region as a warming climate leads to attacks by insects and disease. The trees are “keystone species,” meaning that if they were to disappear, the ecosystem would suffer, devastating Yellowstone’s grizzly bears and harming other wildlife that depend on it as a food source.

2. Crater Lake National Park: Wildfire resilience and resistance

Most of Crater Lake’s forests are considered old growth and have been historically protected from commercial timber harvesting, grazing and road development. Conifers dominate this Oregon park, with multiple varieties of firs, pines, cedars, spruces and hemlock. Natural disturbances — such as wildfire, insects and pathogens — have created a forest mosaic, allowing park visitors to see trees of different ages and sizes. NPCA identified 35,927 acres of mature and old-growth forest in the park, about 20% of the park, and 592,328 acres within 30 miles of its border.

In many fire-adapted forest ecosystems, old-growth trees have survived decades of fire because their thicker bark and other features make them naturally resistant. Old-growth trees often have expansive root systems that help to hold moisture in the soil, and trees’ foliage helps keep forests shaded and temperatures cooler on the ground. As climate change intensifies wildfires across the West, many old-growth trees are more likely to survive and help forests regenerate and remain healthy after a fire.

3. Great Smoky Mountains National Park: Clean water

This park, which straddles North Carolina and Tennessee, is the most biodiverse park in the National Park System. The park’s eight different forest systems cover 95% of the park, with a quarter of that area considered old-growth forest. About 100 species of native trees have been found here, more than in any other national park in North America!

NPCA calculated nearly 200,000 acres of mature and old-growth forest within park boundaries, about 38% of the park, and 513,895 within 30 miles of its border. Albright Grove, on the park’s Tennessee side, is one of the most recognized enclaves of old-growth hardwoods and hemlocks and is accessible by a 3-mile hike.

Old-growth trees help ensure clean water flows through our parks and supplies nearby communities with safe water to drink. The park averages more than 80 inches of rain each year, feeding over 2,100 miles of mountain streams, waterfalls and rivers. Besides enhancing recreational opportunities, this dense annual rainfall supports healthy forests. The root systems of old-growth trees filter water and stabilize river channels to keep clear, cold water flowing. Old-growth forests also slow runoff from storms and hold water in the soil, helping to reduce the impacts of flooding.

4. Yosemite National Park: Climate protection

NPCA calculated about 150,000 acres of mature and old-growth forest in this vast wilderness of California, about 20% of the park, and another 508,703 acres within 30 miles of its borders. A popular spot for visitors to see these giants is Mariposa Grove, located in the southern portion of Yosemite, with more than 500 mature giant sequoias. Giant sequoias aren’t just the largest living trees on the planet, they’re also some of the oldest. Yosemite’s Grizzly Giant is estimated to be around 3,000 years old.

For all this park’s magnificence, Yosemite faces a number of threats from climate change. It ranks fourth among the nation’s most polluted parks, according to NPCA’s 2024 Polluted Parks Report, and is at risk for drought, wildfire and invasive species.

Among the best actions to help curb the effects of climate change is to keep old trees standing. Forests on public lands play a crucial role in removing carbon from the atmosphere and mitigating the impacts of climate change. Old-growth trees sequester an outsized amount of carbon, storing up to 80% of all of the carbon held in forests despite being a small fraction of the total tree population.

5. Mount Rainier National Park: Love for nature’s giants

Whether you are berry picking, bird watching or enjoying a leisurely hike, old-growth forests provide awe-inspiring opportunities to get outdoors.

As one of the first national parks, established in 1899, Mount Rainier is a beloved destination for getting lost in thought amidst its towering trees. It’s no wonder 2.5 million visitors each year come to these ancient forests, filled with Douglas fir, western red cedar and western hemlock.

NPCA identified roughly 74,722 of mature and old-growth forests within the park’s boundaries, about 32% of the park, with an additional 431,143 acres within 30 miles of Mount Rainier’s boundary. Because of these forests, you might see a northern spotted owl or marbled murrelet, two species that rely on old growth for habitat.

The dense canopy and lush understory lead to unparalleled foraging and birding. These ancient trees also make the woods’ earthy scent possible, creating an immersive experience to escape society’s hustle and bustle.

6. Olympic National Park: A category in itself

Olympic National Park may not have lots of neighboring acres of old-growth trees, but it does top NPCA’s list of parks for the most mature and old-growth forest within its boundary. Olympic has 480,977 acres — about 52% of the park and roughly double the amount of acreage of the next park in the same ranking, Yellowstone.

Olympic’s Sitka spruce, western hemlock, Douglas fir and western red cedar spread from mountains to coast. Here you’ll find the world’s largest Sitka Spruce, known as Quinault Big Sitka — measuring 191 feet tall and nearly 59 feet around. Deep in the park’s Hoh Rainforest is an area called the quietest place on earth, surrounded by dense, ancient trees that block out all other sounds.

Where else can you find old-growth forests?

Here is how other national parks stack up. While each park is as distinctive as its forests, it’s safe to say protecting these living giants will ensure they continue to inspire wonder, support healthy ecosystems and combat climate change for generations to come.

• No. 6: Rocky Mountain National Park, with 62,735 acres of mature and old-growth forest within the park and 428,921 acres within 30 miles of its boundary.
• No. 7: North Cascades National Park, with 90,972 acres of mature and old-growth forest within the park and 412,916 acres within 30 miles of its boundary.
• No. 8: Grand Teton National Park, with 22,520 acres of mature and old-growth forest within the park and 402,769 acres within 30 miles of its boundary.
• No. 9: Glacier National Park, with 143,279 acres of mature and old-growth forest within the park and 76,917 acres within 30 miles of its boundary.
• No. 10: Redwood National Park, with 46,899 acres of mature and old-growth forest within the park and 350,339 within 30 miles of its boundary.