In its early years Muir Woods had relatively few visitors, but some of them managed to wreak a fair amount of damage. They drove cars into the canyon and even on side trails; trampled the delicate forest understory and scrambled up steep slopes. They camped, picnicked, built fires, played ballgames, left litter behind, and reportedly even made off with ferns and other plants. By the early 1920s the wear and tear on the park was obvious, leading NPS to close the road into the monument to motor vehicles and horses, and to ban camping.

Park staff unwittingly did their own share of damage. Following what was standard practice at the time, they “tidied” the forest floor and the creek, removing downed trees and picking up branches and other natural debris, thus depriving some plants and wildlife of an important source of nutrients, as well as altering the creek’s flow. In the 1930s, the Civilian Conservation Corps channelized Redwood Creek and built riprap walls to prevent flooding.

By the time Mia Monroe, now the park’s supervising ranger, arrived in 1978, she was struck by the absence of wildflowers, mushrooms, and other wildlife. “There were lots of Steller’s jays,” she said recently, “but no quail, no chipmunks.” Pools where salmon would have been able to lay their eggs had been lost. Clearly, the forest’s ecosystem wasn’t functioning as it should.

There had been troubling signs long before then. In 1971 one of the big redwoods toppled and park staff realized that its premature death might have been caused by visitors trampling the roots. “That was one of the earliest, biggest wakeup calls,” Monroe said. “When a big redwood in a park full of redwoods comes down, you’ve got to pay attention.”

One of the first steps staff took to ease pressure on the forest from its many visitors was to ban picnicking in the 1960s. In the 1970s and 1980s attempts were made to protect the forest floor by paving the main paths and putting up fences to keep people away from trees and the creek. In 1988, volunteers established a native plant nursery and began replanting the trampled forest floor. The compacted soil around the redwoods has been planted with native ferns, redwood sorrel, and other plants that grow in redwood forests. Staff also stopped clearing debris and left fallen trees in place when possible.

In the late 1980s and early 1990s, asphalt was removed from the most heavily used sections of the main trail and boardwalks were built, making the grove more accessible to people with limited mobility while also protecting the trees. An old road and a portion of the main parking lot near the creek were removed. In 1996 and 1998 planned fires were set, returning a key natural process after nearly a century of fire suppression (though prescribed burns were then halted while NPS reviewed its fire management plans, and have not yet been reintroduced). In a redwood forest, periodic fires make room for new trees to flourish, provide nutrients for redwood seedlings, and check the spread of diseases.

Since the improvements began, plants and animals that had disappeared from the forest have been returning--including a pair of river otters that, to the delight of park staff and visitors, gave birth to a pup last year.

Most visitors to Muir Woods probably have no idea that it took more than two decades of hard work to bring the forest to the relatively healthy state they see today. “It was an eye-opener for me,” said Maribeth Halloran, a Mill Valley resident, of a tour that she and a group of volunteers took with Monroe in the summer of 2007. Halloran had been to the park many times over the years, but “I had no idea that they felt they’d gotten to a point where the redwoods were doing more dying than they were regenerating. Now they’re bringing life back. I was really impressed by what they had done to regenerate the forest, on a limited budget.”