Muir Woods National Monument

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The Muir Woods National Monument preserves the last old growth coast redwood forest in the San Francisco Bay Area. The cool moist forest supports a surprising abundance of plant and animal life, from the coast redwood (the tallest type of tree on Earth), to the slimy banana slug, from the amazing Coho salmon to delicate trilliums. This forest refuge welcomes visitors from all over the world to experience the magic of the redwood forest. Until the 1800′s, many northern California coastal valleys were covered with coast redwood trees similar to those now found in Muir Woods National Monument. The forest along Redwood Creek in today’s Muir Woods was spared from logging because it was hard to get to. Noting that Redwood Creek contained one of the San Francisco Bay Area’s last uncut stands of old-growth redwood, Congressman William Kent and his wife, Elizabeth Thacher Kent, bought 295 acres here for $45,000 in 1905. To protect the redwoods the Kents donated the land to the United States Federal Government and, in 1908, President Theodore Roosevelt declared it a national monument. Roosevelt suggested naming the area after Kent, but Kent wanted it named for conservationist John Muir.

Nature & Science

Ecology
Muir Woods is the only old-growth coastal redwood forest in the Bay Area and one of the last on the planet. It is estimated that nearly 2 million acres of forest just like Muir Woods once covered a narrow strip along the coasts of California and Oregon. Today, 97% of this has been impaired or altered and most coastal redwoods now grow on protected second and third growth forests or managed timber plantations. Thanks to William Kent’s preservation efforts, Muir Woods was spared this fate and remains as a very accessible yet prime example of an old-growth forest. The term old-growth is difficult to define. Old-growth cannot solely be determined by size or age of the trees within a forest because these qualities vary widely with species. However, there are four characteristics that slowly develop through time and together define an old-growth forest.

Large Live Trees
The large live trees of an old-growth forest not only stand testimony to the amount of time required to develop into old-growth but also largely determine the structure of the forest. The large trees in Muir Woods are the coastal redwoods, the tallest of all living things and some scattered Douglas firs. The tallest coastal redwood at Muir Woods is about 258 feet, approximately the height of a six foot person stacked head to toe 45 times. Further north, these trees can reach heights up to 367 feet, 60 feet taller than the Statue of Liberty. The average age of the coastal redwoods at Muir Woods is between 600 to 800 years, with the oldest being at least 1100 years old. This is still young for redwoods as they can live up to 2200 years. Being long-lived and large in size, they play a significant role in carbon, nutrient and water cycling in the forest, helping to support an abundance of plants.

Multi-layered Structure
Besides being a collection of immense trees, Muir Woods is a rich community of other interesting plants. An old-growth forest commonly has three distinct layers:

Herbaceous
Understory
Canopy

To better understand this, think of an old-growth forest as a human home: the herbaceous layer is similar to the carpet, the understory like the furniture, while the leafy canopy similar to the roof. Each of these three layers support a different community of plants and each one is well adapted to its position in the forest.

The herbaceous layer of a forest includes the ground cover, ferns and wildflowers. At Muir Woods, the most common plant found in the herbaceous layer is redwood sorrel. This is the plant with the clover-shaped leaves that carpets the ground in the deep shade of the forest. Redwood sorrel is so adapted to the shade that is is actually light intolerant. If the sunlight is too intense, it folds its leaves down like an umbrella instead of spreading them out flat. Other plants in this layer at Muir Woods include western sword fern, western trillium and wild ginger. These plants are important for the health of the forest because they keep the soil moist and protect it from hardening by the sun.

The understory is made of the small trees and shrubs. The common understory plants at Muir Woods are the California bay laurel, big-leaf maple and tan oak. The big-leaf maple has adapted to the low light by producing the largest leaves of any maple tree, which help to capture as much light as possible. The California bay laurel deals with the low light by developing a root system that allows the tree to lean towards openings in the forest canopy. The tan oak has developed a special structure in its leaf that allows it to effectively use the light that filters down from the canopy. The understory is very important for animals such as the endangered northern spotted owl. This owl is usually only found in old-growth forests because it can use the understory layer to protect itself from predation and competition.

The large redwood trees of Muir Woods dominate the canopy layer. On average, each tree requires between 200 to 500 gallons of water per day and can even use up to 2,000 gallons. Winter rains usually bring 40 inches of precipitation per year, but during the summer months there is very little rain. The trees must then utilize the moisture within the frequent coastal fog. With their drooping branches and channeled leaves, the trees capture the moisture in the fog and direct 10 to 20 inches a year down to their roots. Another adaptation to the canopy is the coastal redwood’s two distinct leaf structures. Near the top of the tree, the leaves are very short and compressed, helping to protect them from the wind and drying out in the sun. On the bottom half of the tree, the leaves are much larger and spread out, allowing the remaining light to be captured. These leaves help the coastal redwood to be so effective at capturing light that it can grow anywhere between 1 to 6 feet each year once it reaches the canopy, making it one of the world’s fastest growing trees. The canopy layer is important because it creates a constant mild and moist climate for the ecosystem, while providing protective cover for the animals moving among the trees.

The multi-layered structure of an old-growth forest helps these ecosystems support a specialized population of plants. While an old-growth coastal redwood forest does not have as many plant species as a tropical rain forest, it instead has 2 to 10 times more living matter per given volume.

Dead Trees
It was not long ago that the National Park Service used to remove all dead material from this forest to keep it clean and reduce fire threat. However, dead trees are vital for the forest and take many different forms. They can fall and become part of the forest floor and aquatic community or can remain standing, becoming what is known as a snag.

The trees that fall to the forest floor are important because they help keep the soil moist by soaking up rainwater as well as serving as a shelter for many of the insects, amphibians and mammals in the forest. They continually replenish the soil by slowly releasing nutrients. One of the most important roles for these fallen trees is serving as a nursery for young seedlings. As the logs lie on the ground, leaves and cones accumulate on top, slowly decomposing and turning into soil. Seeds fall into this fertile soil, growing into young seedlings. Other trees fall into the creek, creating the habitat diversity necessary for a healthy stream by forming falls and pools. The downed logs help to capture debris, lessen impact of floods and release nutrients.

The dead trees that remain standing are home to many insects, birds and mammals. Insects feed on these trees, which in turn give the pileated woodpeckers plenty of food to prey on. There are several species of bats that roost under the loose bark and hollows of snags. Hawks, owls and eagles use snags as a perching platforms. Even animals such as the bobcat find shelter in the larger cavities of a snag. Eventually, the tree will fall and assume a new role as a downed log.

The importance of a tree does not diminish after it has stopped living. It is a common saying here at Muir Woods that only half the life a tree is spent standing, while the other half is spent on the ground.

Interdependent Communities
All the different components of an old-growth forest are dependent on one another. The large live trees depend on the downed logs for water and much of their nutrients. Plants like redwood sorrel and California bay laurel rely on the multi-layered structure of the forest for protection and sunlight.

An old-growth forest is also itself very interconnected and through time, many of the plants and animals become reliant on one another. One example at Muir Woods is found in Redwood Creek. The redwoods depend on the creek for most of their water and the trees help keep the gravel in the creek clean by stabilizing the soil. The trees also help keep the temperature of the stream cool and constant. As the trees die and fall into the creek, they create pools and enrich the stream with their nutrients. Since salmon need clean gravel, constant water temperature and pools for spawning, Redwood Creek provides good habitat for salmon. It is one of the last streams in California to still have its native stock of salmon, due largely to the undisturbed forest around us. An old-growth forest is more than just large trees, it is an interconnected and diverse community of plants and animals.

An old-growth forest is not only a product of a vast amount of time, it is also a result of several other factors, such as adaptation and luck. Even the most highly adapted forest could not withstand repeated disturbances. This makes old-growth very rare in the cycles of nature, but even rarer when humans are included in the picture. In the past, humans have only viewed old-growth forest in terms of economics. However, current research highlights many other important benefits of old-growth forests. These forests provide habitat for hundreds of birds, mammals, amphibians, reptiles, insects and plants. They minimize soil erosion, produce clean water and air and maintain high biological diversity, which is crucial for this planet.

Recreation

Muir Woods canyon is a place to walk and enjoy the forest. The primary trails along the canyon floor are level and paved. Bridges along Redwood Creek create leisurely 1/2 hour, 1 hour, or 1 1/2 hour loops. All of these walks take you on a journey beneath 1000 year old old-growth coast redwood trees. Muir Woods is visited by over 1 million people each year. Visitation is highest in summer months; park staff recommends visiting on weekdays, before 10:00 a.m. or after 4:00 p.m. to avoid the crowds.

The redwood forest is usually cool. Jackets, layered clothing and walking shoes are advised.

Picnicking is not allowed in Muir Woods, but there are picnic facilities nearby at Muir Beach and Muir Beach Overlook.

All pets, including dogs, are prohibited in Muir Woods and Mt. Tamalpais State Park. Guide dogs and service dogs are allowed in Muir Woods.

Bikes are not allowed in Muir Woods. They are allowed on designated fire roads surrounding Muir Woods.

Getting There

Muir Woods National Monument is one of the busiest National Parks in the country. Over 1 million people go through the entrance gate each year. Parking near the monument is limited. On summer weekends, once our parking lots are full, you may expect to park up to a mile down the road. We suggest coming before 10:00am or after 4:00 p.m. or on weekdays to avoid the biggest rush.

From San Francisco, Peninsula, or South Bay
Take Highway 101 North across the Golden Gate Bridge. Exit Highway 1/Stinson Beach (there will be a sign for Muir Woods at this exit). Drive about .5 miles. At the stoplight, turn left. Drive about 2.7 miles. At the top of the hill, turn right towards Muir Woods/Mount Tamalpais. Drive about 0.8 miles. At the 4-way intersection, turn left towards Muir Woods (oncoming traffic has the right of way!). Continue down the hill about 1.6 miles. The Muir Woods parking lot will be at the bottom of the hill, on a sharp turn, on your right.

From Berkeley, Oakland, or East Bay
Take Interstate 80 North from the Bay Bridge. Exit Interstate 580 West for the Richmond/San Rafael Bridge. Exit Hwy 101 South. Exit Highway 1/Stinson Beach (there will be a sign for Muir Woods at this exit). Drive about .5 miles. At the stoplight, turn left. Drive about 2.7 miles. At the top of the hill, turn right towards Muir Woods/Mount Tamalpais. Drive about 0.8 miles. At the 4-way intersection, turn left towards Muir Woods (oncoming traffic has the right of way!). Continue down the hill about 1.6 miles. The Muir Woods parking lot will be at the bottom of the hill, on a sharp turn, on your right.

From San Rafael, Santa Rosa, or North Bay
Take Highway 101 South. Exit Highway 1/Stinson Beach (there will be a sign for Muir Woods at this exit). Drive about .5 miles. At the stoplight, turn left. Drive about 2.7 miles. At the top of the hill, turn right towards Muir Woods/Mount Tamalpais. Drive about 0.8 miles. At the 4-way intersection, turn left towards Muir Woods (oncoming traffic has the right of way!). Continue down the hill about 1.6 miles. The Muir Woods parking lot will be at the bottom of the hill, on a sharp turn, on your right.

From Stinson Beach, Olema, or Highway 1 North
Take Highway 1 South towards Muir Beach, about 9 miles from Stinson Beach. Turn Left at Frank Valley (Muir Woods) Road (if you reach the Pelican Inn you’ve gone too far). Drive about 2.5 miles to the Muir Woods parking lot.

Traveler Facts

Contact Information
Muir Woods National Monument
Mill Valley, CA 94941
Phone: 415-388-2595
Fax: 415-389-6957

Operating Hours & Seasons
Muir Woods National Monument is open from 8:00 a.m. to sunset, including holidays.

Weather/Climate
Muir Woods National Monument is cool, shaded and moist year round. Daytime temperatures at Muir Woods average between 40 and 70 degrees Farenheit.

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