Muir Woods National Monument

The Muir Woods National Monument is an old-growth coastal redwood forest. Due to its proximity to the Pacific Ocean, the forest is regularly shrouded in a coastal marine layer fog, contributing to a wet environment that encourages vigorous plant growth. The fog is also vital for the growth of the redwoods as they use moisture from the fog during droughty seasons, in particular the dry summer.

The monument is cool and moist year round with average daytime temperatures between 40 and 70 degrees Fahrenheit (4 to 21 °C). Rainfall is heavy during the winter and summers are almost completely dry with the exception of fog drip caused by the fog passing through the trees. Annual precipitation in the park ranges from 39.4 inches (1,000 mm) in the lower valley to 47.2 inches (1,200 mm) higher up in the mountain slopes.

The redwoods grow on brown humus-rich loam which may be gravelly, stony or somewhat sandy. This soil has been assigned to the Centissima series, which is always found on sloping ground. It is well drained, moderately deep, and slightly to moderately acidic.[7] It has developed from a mélange in the Franciscan Formation.[8] More open areas of the park have shallow gravelly loam of the Barnabe series, or deep hard loam of the Cronkhite series.[9]

Undergrowth of a redwood canopy demonstrating the deep shadow under the trees. Note the clearing in the background showing other trees growing in the light.

The main attraction of Muir Woods are the coast redwood (Sequoia sempervirens) trees. They are known for their height, and are related to the giant sequoia of the Sierra Nevada. While redwoods can grow to nearly 380 feet (115 m), the tallest tree in the Muir Woods is 258 feet (79 m). The trees come from a seed no bigger than that of a tomato seed.[15] Most of the redwoods in the monument are between 500 and 800 years old. The oldest is at least 1,200 years old.

Other tree species grow in the understory of the redwood groves. Three of the most common are the California bay laurel, the bigleaf maple and the tanoak. Each of these species has developed a unique adaptation to the low level of dappled sunlight that reaches them through the redwoods overhead. The California bay laurel has a strong root system that allows the tree to lean towards openings in the canopy. The bigleaf maple, true to its name, has developed the largest leaf of any maple species allowing it to capture more of the dim light. The tanoak has a unique internal leaf structure that enables it to make effective use of the light that filters through the canopy.

Redwood Creek

Redwood Creek provides a critical spawning and rearing habitat for coho or silver salmon (Oncorhynchus kisutch) and steelhead (Oncorhynchus mykiss). Steelhead are listed as threatened species (2011) in the Central California Coast distinct population segment. Coho salmon are listed as endangered in their evolutionary significant unit (2011). The creek is near the southernmost limit of coho habitat and the fish have never been stocked, so they have a distinctive DNA. The Redwood Creek salmon are Central Coast coho salmon which have been listed as federally threatened species since October 2006 and as federally endangered species in June 2005. Coho migrate from the ocean back to freshwater for a single chance at reproduction, generally after two years in the ocean. The spawning migrations begin after heavy late fall or winter rains breach the sandbar at Muir Beach allowing the fish to move upstream (usually in December and January).[16] No salmon were seen in the 2007–2008 winter run, nor the 2008–2009 winter run. Evidence points to exhaustion of smolt oversummering in the creek due to a loss of large woody debris and deep pools where young salmon can rest. Starting in 2009, the National Park Service began restoring Muir Beach to create a functional, self-sustaining ecosystem and improve visitor access.[17] The intervention was almost too late, since the coho only has a three-year life span. But, as of January 2010, and for the first time in three years, an estimated 45 coho swam up Redwood Creek to spawn, creating 23 redds or clusters of eggs.[18] In 2011, 11 live adult coho and 1 coho carcass was observed, along with three redds, a modest increase over the 2007-2008 spawning season.[19] Statewide the coho population is 1% of its levels in the 1940s and the fish have vanished from 90% of the streams they formerly visited.[20][21] The Watershed Alliance of Marin reported that no salmon returned to spawn in 2014, prompting concerns that the fish may now be extirpated from the creek.[22]

Muir Woods is home to over 50 species of birds.[23] This relatively low number is due to the lack of insects. The tannin in the trees repels the insects and the volume of flowers and fruits produced by plants below the canopy is limited by the shade of the redwoods.

It is occasionally possible to see northern spotted owls or pileated woodpeckers in the forest. While decreasing in numbers elsewhere, the spotted owls appear to be thriving in the monument and other evergreen forests in the area. A National Park Service monitoring project of the owls is ongoing within the monument. The project has found that adult owls are finding mates, raising young to adulthood and the young are having new broods of their own.

Banana slugs are common in Muir Woods

The monument is home to a variety of mammals ranging in size from the 4 inch American shrew mole to the (much larger) black-tailed subspecies of mule deer, Odocoileus hemionus columbianus.[24] The majority of the mammals are nocturnal or are burrowing animals living under the ground or the dense litter on the forest floor. Most commonly seen are Sonoma chipmunks, and western gray squirrels.[25]

Bears historically roamed the area but were largely exterminated by habitat destruction. In 2003 a male black bear was spotted wandering in various areas of Marin County, including Muir Woods.

There are 11 species of bats that call the monument home, often using hollows burned into the redwoods by past fires as a maternity colony.

In November 2010 sea otters (Enhydra lutris) have been spotted swimming in the new stream channel constructed in the lagoon area of Redwood Creek.[18]

Reservations are required for all vehicles and shuttle riders since 2018. Marin Transit operates a shuttle on all weekends and holidays and during select peak weekdays, providing service to Muir Woods from Sausalito, Marin City, or Mill Valley (Route 66); the National Park Service recommends that visitors use the shuttle when it is operating to avoid difficulties in finding parking.

The NPS requires reservations made in advance for all vehicles and shuttle riders; a parking reservation is $8.50 per vehicle while a spot on the shuttle is $3.25 per person. Furthermore, an entrance fee of $15.00 per person is charged in order to gain entry to Muir Woods. The shuttle service and park are open every day of the year including holidays. The park is open from 8:00 am and closes at sunset.

There are no camping or lodging facilities in Muir Woods.[29] The monument is a day-use area only. There are camping facilities in the adjacent Mount Tamalpais State Park.

• Restrooms located in entrance plaza and cafe
• Muir Woods Trading Company cafe and gift shop – offers deli food items and souvenirs. The cafe also has a permanent display of historic photographs.
• The main trail (paved and boardwalk) through Muir Woods is a 2 miles (3.2 km) loop. A .5 miles (0.80 km) loop from the Visitor Center, through Founders Grove, to Bridge 2 and back is ADA accessible.

• The Visitor Center, located in the entrance plaza, features permanent and changing exhibits on redwood ecology and conservation, as well as a store selling books and gift items.

Canopy created by the trees

One of the paved trails in Muir Woods

The paved/boardwalk main trail begins at the entrance plaza (Trail Map) and travels into the old growth redwood forest alongside Redwood Creek. Other unpaved walking trails extend from the main trail to connect with Mt. Tamalpais State Park trails outside of the monument boundaries.[30]

Bicycles are only allowed on designated fire roads.

The annual Dipsea Race, a footrace which goes between Mill Valley and Stinson Beach, passes through Muir Woods on the second Sunday in June. The Double Dipsea, later in June and the Quad Dipsea, in November, follow the same course.

Sunlight on leaves and spider webs in Muir Woods

Annual Recreational Visitors

Rangers and volunteers present 15-minute interpretive talks and guided one-hour tours when staffing permits. Program topics include redwood ecology and conservation, the impact of climate change, and the history of Muir Woods. Longer hikes or other special programs are offered several times per month, and require a reservation.[31]

Weddings, commercial filming, and special events are allowed in the monument only with a proper permit.[32]

In 2018, more than 17.5 million visitors visited Golden Gate National Recreation Area, Muir Woods National Monument, and Fort Point National Historic Site, and spent $1.2 billion in communities near the parks. The protections given to these areas by the federal government helped to  establish them as natural tourist destinations creating an attraction that brought positive externalities in the form of increased business to the surrounding communities.  According to the National Park Service, the spending and cash flow brought to the area through these visitors created 12,658 new local jobs and had a net benefit of $1.6 billion in additional revenue.[33]

A peer-reviewed visitor spending analysis was conducted by economists Catherine Thomas and Egan Cornachione of the U.S. Geological Survey and Lynne Koontz of the National Park Service. The report shows $20.2 billion of direct spending by more than 318 million park visitors in communities within 60 miles of a national park. This spending supported 329,000 jobs nationally; 268,000 of those jobs are found in these gateway communities. The cumulative benefit to the U.S. economy was $40.1 billion.[34]

The popularity of Muir Woods as a tourist destination has created a great deal of congestion and delay on the two lane California State Highway 1. As a result, many civilians and residents living near Muir Woods and affected by the increased traffic on the pathway to the national monument have voiced concern with the National Park Service. In response, policy was designed that would create a parking reservation system, detailed road shoulder parking limits and enhanced parking enforcement in order to combat the negative externalities caused by Muir Woods.

However, according to the Mount Tam Task Force, created to address the traffic concerns created by Muir Woods, the policy aimed towards fixing the issue has proved ineffective. The introduction of a website where all parking and shuttle reservations can be made, has helped to decongest the traffic to an extent.[35] Despite the number of attending visitors trending downward at Muir Woods, parking and congestion remain a problem for tourists and locals alike.[36]