As a certified forest therapy guide who helps people experience how healing immersion in nature can be, I often invite my forest bathing participants to share an experience with an old tree. Some recall being awed after standing next to or craning their necks to look at the top of one of California’s towering coastal Redwoods. Others remember the impossibility of wrapping their arms around an almost 300-year-old hemlock tree in Pennsylvania’s Allegheny National Forest. Still others recall the dappled light shining down on them through skyscraper-like tree canopies.
The definition of “old growth” varies depending on the organization and context. The Bureau of Land Management and the U.S. Forest Service define old growth for pinyon and juniper woodlands as 150 years and older, for example. Experts agree that, regardless of the tree species, old-growth forests have developed over long periods, often centuries, without significant disturbance by human activity. They’ve been shaped by natural ecological processes like floods, fires, strong winds and the death of old trees.
But old-growth forests contain more than just long-lived trees. They are natural mosaics that include young- and middle-aged timber that create multilayered canopies, fallen “nurse” logs that host the next generation of seedlings, organically rich soil and a diverse shade-tolerant plant understory. You’ll also find dead-standing trees called “snags,” that provide animals with shelter and lookout points and fallen trunks that create “canopy gaps” that help establish new trees and plants, maintain habitat diversity and drive crucial long-term regenerative processes that create resilient forests. (Mature forests are so-called when they begin displaying many of these same attributes, according to the U.S. Forest Service: “The mature stage … generally begins when a forest stand moves beyond self-thinning, starts to diversify in height and structure, and/or the understory begins to reinitiate.”)
Benefits of Old-Growth Forests
Old-growth forests are examples of the power of diversity to create resilient ecosystems. Here are some ways they benefit human and ecological well-being:
- Old-growth trees more efficiently curb carbon and pollution. Older trees’ superior ability to capture and store carbon and mitigate pollution can improve air, soil and water quality.
- Mixed-age forests help maintain biodiversity. Trees provide food and habitat for a wide range of animal species—including threatened and endangered ones, like the spotted owl and Canada lynx—and old and dead trees can support a wide range of plant and fungus life. The more diverse a forest’s ecology, the less susceptible any one species may be to pests, disease or destruction.
- Large, established root networks can prevent erosion. Old-growth forests’ vast underground root networks have been shown to slow soil runoff from water, wind
,and snowmelt. They can also absorb rainfall, helping retain moisture in the soil.
- Old-growth trees’ ancient histories have meaning to various communities. For example, culturally modified trees, which have been intentionally altered by Indigenous people, have specific cultural significance and are even legally protected in some places.
- Untouched forests offer recreational and community-building opportunities. Some of the country’s best hiking trails, dispersed camping, forest bathing and ecological education are found within older, unblemished woodlands.
Threats to Old-Growth Forests
In 1630, half of the United States was covered by forests. Yet old-growth-forest numbers have declined annually since European settlement. A 2023 analysis conducted by the U.S. Forest Service found that old-growth forests represent 19% of forested land overseen by agency and the Bureau of Land Management, with mature forest another 45%. During the past century alone, human threats like repeated logging, real-estate development or “sprawl,” wildfire suppression tactics, and removal of Indigenous populations from their homelands have drastically reduced the number of old-growth and mature trees in the U.S.
Climate change and other environmental factors also challenge old-growth and other forests. For example, extreme heat and drought-related stress cause defoliation, scorch, wilting and minimized photosynthesis. Longer and more widespread wildfire seasons increase forest mortality as well. Non-native insect infestation and disease exposure can impact vulnerable trees stressed by drought, heat and other conditions.
Remaining Old-Growth Forests in the U.S.
While humans have carved up old-growth forests and natural threats have grown, pockets of these venerable groves still dot the country. They’re often in landscapes challenging for humans to access, like mountain ranges or protected on public lands.
Here are some of the most beloved mature woodlands remaining in the United States:
- Appalachia: The Great Smoky Mountains, including Albright Grove, contain tracts of old-growth hardwoods.
- California: Big Basin Redwoods State Park in the Santa Cruz Mountains is home to about 4,300 acres of old-growth redwoods, and Pfeiffer Big Sur State Park features old-growth redwood, bay laurel, live oak, sycamore, cottonwood, maple and alder.
- East Coast: Nestled in Massachusetts’ Berkshires, Mohawk Trail State Forest is believed to house the tallest white ash and American beech in the Northeast.
- Upper Midwest: Porcupine Mountains Wilderness State Park contains 60,000 old-growth acres of pine, hemlock, yellow birch, basswood and sugar maple.
- Pacific Northwest: The Olympic National Park in Washington offers multiple access points to old-growth temperate rain and lowland forests that are home to Douglas fir, Sitka spruce, western white and lodgepole pine and western hemlocks, some up to 1,000 years old.
Protect These Vital Ecosystems
The ongoing threats to old-growth forests make maintaining current acreage and restoring degraded areas critical. It’s also vital to protect mature forests—which currently accounts for 45% of U.S. forested lands—so they can one day develop into old-growth groves.
While the U.S. Forest Service’s public-comment period ends on September 20, 2024, there is still time to join the REI Cooperative Action Network in a petition calling for the proposed National Old-Growth Amendment to include guidance on logging in old-growth and mature forests. This amendment would be included in an Environmental Impact Statement to develop a collaborative, climate-informed and science-based process for safeguarding these irreplaceable forests and their ecological, cultural and health benefits for future generations.
There are other actions you can take every time you visit old-growth woods—or any outdoor recreation area, for that matter.
- Follow the Leave No Trace principles. These guidelines help us keep wild spaces wild, prevent ecosystem destruction, keep invasive species at bay and more.
- Practice wildfire safety all year—not just during “fire season.” Fire can quickly devastate old-growth forests, erasing centuries’ worth of ecosystem development in a matter of moments. Always control your fire, alert authorities immediately when there is sign of fire, and dispose of ashes and firewood properly.
- Shop for Forest Stewardship Council-certified (FSC) products. FSC is a global organization that certifies forests based on rigorous standards of responsible forest management. FSC certification applies to wood and wood-based products and covers a broad range of topics, including environmental stewardship, legal and regulatory compliance, social and economic well-being of workers, indigenous people’s rights, and social and economic well-being of communities. You can find the FSC logo on both a product and its packaging.
- Find a stewardship opportunity near you—or plan a trip around one. Volunteering to do trail maintenance is not only a good excuse to get your hands dirty and spend the day outside, it’s also a powerful way to connect with the natural world and honor your place as its ally and protector. Projects like invasive species abatement, trail maintenance and graffiti removal can help preserve forests’ beauty as well as their delicate life balance. Visit volunteer.gov to find a variety of opportunities to pitch in nationwide.