Fire in the Forest

 

During a visit to Muir Woods, you may notice charred scars on redwood trunks. In some cases, entire trunks are split open, their insides blackened by charcoal. These clues reveal a story of fire in the forest - one that many may not expect. This natural force has shaped not only our park and redwood forests like it, but ecosystems across the world.

 

Notice the black scars on the base of the trunks in this image. Fire is a natural, necessary force in old growth coast redwood ecosystems. The trees are resilient and may show signs of being burned decades or even centuries after experiencing fire.

NPS/ Steve Olson

Fire plays a critical role in maintaining ecosystem health at places like Muir Woods.

Imagine a forest on fire - it’s probably scary! For decades, land managers have practiced fire suppression, misunderstanding fire as harmful. Today, a concept called fire ecology helps us understand the benefits of fire and how it shapes the world we live in. Fire Ecology is the study of fire as an ecosystem process. It explains the ways in which fire can be beneficial to an ecosystem, under the right conditions.

For example, burns can create space for new seedlings. In some cases, seeds waiting years - or even decades - are awakened by fire and grow into a superbloom. These plants adapted to fire are called pyrophites. Some pyrophile plants depend on smoke or high temperatures to distribute seeds or sprout. Even animals may benefit: fire makes cavities in trees that can become important habitat. Redwoods are uniquely well-adapted to fire.

Fire regime explains an ecosystem’s relationship to fire, specifically its frequency (how often fire occurs), intensity (how hot the fire burns), and severity (how impacted the ecosystem is by fire). Every ecosystem has a specific dependence on these variables, and altering the presence of fire can have significant ramifications. For example, research around Muir Woods shows that this area experienced regular burns every 22-27 years. But this area has experienced very few fires since the early 1800s - so what changed?

 

Prescription fires at Muir Woods, as depicted in this photo from October 11, 1985, have occurred only a few times since the park's founding in 1908. Before, native Coast Miwok people long practiced cultural burns to maintain forest health. The tribe continues to shape stewardship practices today.

NPS/ Jim Morley

A Legacy in the Landscape

Fire has long been integral to the way of life for many Native American people. Across the continent, records show how indigenous cultures have practiced what we call today “cultural burns.” This term refers to the regular and intentional use of small, controlled fires to ensure the long-term wellbeing of plants and animals. Their use of fire has shaped entire ecosystems, including the old growth coast redwood forest found at Muir Woods.

Here, the Coast Miwok have inhabited the area for over 8,000 years and continue to shape and steward the landscape today. In the OneTam Forest Health Strategy published in 2023, Dr. Peter Nelson, a member of the Federated Indians of Graton Rancheria, writes: “it is imperative to work with the Tribe to plan and implement prescribed burns informed by Traditional Ecological Knowledge.” He continues: “Fire suppression alone cannot address the fire crisis in the Western United States, and so land managers need to be working with the Tribe to steward these areas in more sustainable ways.”

Prescribed Burns: fire as medicine

Today, land managers like National Park rangers will intentionally ignite fire after careful planning and under very specific conditions. These are called prescribed fires or sometimes controlled burns. Like cultural burns, a prescribed fire is like medicine from a doctor, but for the forest - a specific dosage as part of a unique treatment plan to ensure long-term health.
Prescribed fires are carefully monitored by experts and are intended to meet specific objectives. These goals include reducing buildup of dead and downed vegetation, promoting growth of native plant species, improving habitat for animals, and removing nonnative plant species.
They are very different from wildfires. Wildfires will be monitored by experts who may take suppression actions - especially if they risk threatening human life, property, or burn so intensely that they can damage ecosystems. In cases where wildfire can provide benefits to the land, experts may work to “steer” a wildfire without extinguishing it - like if the fire is far from infrastructure and burning an area where fire is natural.
In the last few years, California has seen a record breaking fire season. The severity of fires and prolonged fire season are a direct result of human caused climate change and malpractice stewardship of our lands. To respond to this heightened threat, land managers may use tools like prescribed burns. While the ancient trees are well-equiped to surive fire, these regular fires reduce the risk of catastrophic megafires.

 

Redwoods have a number of traits to help them survive fires. For example, they have a unique ability to clone themselves from lumps on the trunks called burls. From burls, new shoots will emerge after the tree experiences stressors like fire.

Randy Widera

Old-Growth Redwood Forests: adapted to survive

Many ecosystems around the world have developed alongside fire, but old growth redwood forests respond especially well to fire. This is due to both adaptations in the trees and what they do in their ecosystem.

Redwood trees have 3 notable adaptations that help them survive. The bark of a redwood can be up to a foot thick. This outer layer is full of fibers that insulate well against the heat of fire. Its rich reddish-brown color comes from tannins.

Tannins are a complex chemical found in bark as well as wood, needles, cones, and more. They help trees resist decomposition, insects, and fire. On a chemical level, tannic acid acts as a flame retardant, slowing the rate at which fire can consume redwoods. Whereas other trees may need oils to repel insects or sticky resin to protect themselves, the redwoods don’t have much of either - further decreasing the risk of catching fire.

Additionally, coast redwoods grow features called burls. These masses of dormant bud tissue serve various roles. Some burls are like scars, allowing the tree to heal over the open wounds caused by forest fires. Other burls help the tree quickly resprout in the case of stress or damage. Thanks to these burls, redwoods can regrow fresh stems and green needles at any point on their trunk, putting the forest on a fast track to recovery.

 

By restoring burn practices to the landscape, land managers facilitate conditions for a healthy ecosystem resilient to climate change. The trees themselves offer an inspiring model of how we can show care to our community.

Save the Redwoods League/ Sashwa Burrous

An old growth redwood forest also features characteristics that benefit the whole ecosystem. During your visit to our park, notice how the largest trunks don't have many branches close to the forest floor. A healthy old growth redwood forest also has ample space between clusters of trunks called family circles. Together, these characteristics improve the odds that a fire will stay small and close to the ground - the ideal conditions of a beneficial burn.

More forest magic takes place at the top of the tall trees, where specially-shaped needles capture something unexpected. Whereas the lowest branches on the tree are wide and flat to absorb sunlight, the highest have small needles on branches shaped like a broom. The different arrangement is well-suited to sweep the sky for moisture from fog, which is typically common in the summer. Some of the condensation is absorbed directly into the needles, while much of it drips to the forest floor. This redwood-engineered rain ensures cool, damp conditions year-round. As a result, the entire ecosystem is better equipped to survive a fire.

In contrast, imagine an unhealthy forest, like one recovering from a logging operation. Clear-cut redwood forests typically feature trees regrowing close together with dense foliage known as ladder fuels. Now imagine a forest fire in this scenario. Flames could climb hundreds of feet high into the canopy, resulting in a very dangerous fire. In these conditions, even the plants adapted to fire will struggle to survive.

Spectacular and complex adaptations have helped redwood forests thrive for millions of years. But unsustainable consumption of natural resources like forests and fossil fuels have resulted in contemporary challenges that require human action to address. Fortunately, people before us have blazed a path for us to follow today. Implementing prescribed fires is one practice to achieve long-term ecosystem health.

 

Commonly Asked Questions about Prescribed Fire

Why do rangers conduct prescribed fires?

Where do rangers conduct prescribed burns?

How do rangers control the fire?

How does the smoke from a prescribed fire get managed?

Why might rangers postpone a scheduled burn?

 

Additional Resources

• For more information about ecosystems across Marin and their stewardship, check out the OneTam Forest Health Strategy. If you're especially interested in how the Tribe has cared for this area - and about the role they play today - read chapter 3.

• Curious about traditional ecological knowledge and cultural burn practices more generally? Visit the NPS webpage dedicated to the topic: Indigenous Fire Practices Shape our Land.

• For educators to discuss the beneficial impacts of fire, here's a teaching tool and classroom guide on Appreciating Cultural Burning & Good Fire developed by the Redbud Resource Group, a Native-led organization focused on public health, land stewardship, and education.

• Interested in what you can do to keep your own personal residence safe? A key step to take is to develop defensible space around structures, work Muir Woods completed in late 2024. Here's more information on how to protect yourself, your home, and your community from our colleagues at FireSafe Marin: Preparing for Wildfire.

• If you're especially excited about the future of prescribed fire, consider becoming a practitioner yourself! In Marin, our neighbors at All Hands Ecology launched the Fire Forward program to train community members on how to implement good fire. After all, private and commuity-held land can benefit from burns as much as public lands do.