Mt. Tamalpais is home to over 1,000 native species of plants and animals and has become a bustling local monument filled with locals and tourists alike. But at what cost? Mt. Tam is now visited by over a million people per year, a number that rises rapidly and has long-lasting effects on the ecosystem. An increase in trail users has led to increased strain on trails, more trash, and finally increased illegal, or social, trail building. The aforementioned issues have caused greater problems, such as erosion and threats to native wildlife.

Hugh Kuhns, a Mill Valley resident, took it upon himself to create a more sustainable ecosystem of trails,

“I had email addresses of a couple thousand people … and out of that, we created an organization called the friends of the steps lanes and paths,” Kuhns said. Kuhns and many other residents work together to maintain the Steps, Lanes, and Paths (SLPs) every month to make sure they are accessible for all, especially during an emergency.

The trails Kuhns works on have seen a tremendous increase in users in recent years, mostly linked to tourism, that have both positive and negative effects. On a good note, trail usership has boomed, especially in Muir Woods where the annual number of guests has risen by over 30percent during the past 10 years alone, according to the National Parks Service.

The increase in trail users has its downsides, such as an increased number of invasive species, fire danger, and erosion of trails. Non-native animals dominate the food chain and leave local animals without a food source and slowly kill off the native population. In addition, invasive plants can grow on, or near, native plants and root themselves deep in the ground, sucking water and other nutrients from the original inhabitants. Invasive species have two main ways of getting into an ecosystem, by the feet of trail users or by being planted in a garden. Both of these have been recognized as threats to plant life on Mt. Tam by One Tam, an organization that researches and then analyzes data to find the health of Mt. Tam.

In One Tam’s most recent study, in 2016, they found that Mt. Tam is in fair condition, meaning that “While some of the mountain’s plants and wildlife are thriving, others are suffering the effects of invasive species, plant disease, altered fire frequencies, and climate change. The condition of others, such as invertebrates and bats, remains largely unknown,” according to their website.

The grasslands on Ridgecrest Boulevard have been labeled as a high-risk area as plant invasion, such as the coyote brush, a three- to 10-foot bush with yellow flowers that will most likely expand rapidly in the coming years if no work is done to prevent the local grasses from being wiped out. This serene stretch of road overlooks Stinson Beach and a quick search on Instagram will prove its notoriety among Tam students and tourists alike. These grasslands are rare in our local ecosystem, taking up only 1 percent of the land they used to hold in California. Despite this, they are integral to Mt. Tam as they provide a habitat for 90 percent of California’s rare plants across the state. 

Other ecosystems on Mt. Tam, such as the redwood forests and oak woodlands, are experiencing declining health as a result of sudden oak death. Sudden oak death is caused by Phytophthora ramorum, an algae that attaches itself to the bark of a tree and causes the aforementioned disease. Additionally, climate change, another human-driven impact, will dictate which species survive as temperature, precipitation, and changes in fog patterns will force plants and animals to adapt.

The aforementioned redwood forests are predicted to be impacted by climate change because of their reliance on water, according to Emily Francis, a Ph.D. student at Stanford. The redwoods were previously impacted during the recent drought California underwent as a result of differing fog patterns and will most likely suffer during droughts in the near future if our climate continues to heat up.

“Old-growth forests are important to society for many reasons, but their worth cannot be measured,” Francis said.

A third human-related impact is the undoubtable fire risk that will eventually affect Mt. Tam. Mountains undergo cycles where fire happens and burns through, clearing debris from the ground and preventing a major fire from happening in the future. As humans, we have fought off fires, leading to a buildup of debris, meaning that once a fire is ignited it will be greater than the mountain has ever experienced. This is an especially big threat to the oak woodlands environment, as these areas are at the greatest risk of fire as the density of plant life is greater than anywhere else. This threat is exacerbated by the fact that barbeques are a common sight on the mountain and not everyone is careful about controlling their burn. 

Furthermore, trail users, such as mountain bikers and equestrians, pose different threats to the trails of Mt. Tam, though there is debate over whether these are based on facts or fear.

“The mountain bikes are super fun but they also have a tendency to create ruts … mountain bikers like to go right down,” Kuhns said. This statement relates to the many illegal trails created by bikers to make a trail more exciting, cutting out tight corners in favor of a steeper, more technical route. 

Mountain biker and Marin Conservation League member Larry Minikes said, “There are only a few studies on the effects of mountain bikes … it is so different on every mountain.” He noted studies from British Columbia and Idaho, two places with vastly different mountain surfaces and levels of trail users. British Columbia is a bustling region with a mixed terrain while much of Idaho’s mountain biking is a granite surface and is seen by fewer people. Minikes believes that we shouldn’t base Mt. Tam’s rules of these studies and should instead do our own research for the most accurate data. 

A third mountain biker living in Mill Valley, Cal Deam, took the position that bikes have almost no more impact than hikers.

“First, most anti-bicycle advocates would say that mountain bikes are bad for trails and cause erosion. There has been no study linking bikes to increased soil damage on trails. The only two conclusions are that hikers do minutely less damage to the trail itself, but tend to step outside of the trail and trample the surrounding flora and fauna,” Deam said. “It seems worse to trample healthy plants than to do slightly more damage to a trail, where everything within the trail is already dead. As for erosion, this mostly happens when people do not stay directly on the trail, so logically hikers would be more prone to causing erosion.” 

Finally, horses are another heavily discussed topic with two schools of thought. “The effect of horses is negligible, the MMWD trucks do more damage,” Minikes said. On the other hand, Deam said, “Horses have definitely been proven to cause much more erosion and trail damage than both bicycles and hikers.” 

Tam High science teacher John Ginsburg backed Deam’s opinion and said, “The biggest issues with horseback riders is when they take their horses out on wet days and create huge muddy areas along the trails.” Ginsburg believes that a solution to the erosion issue layed out earlier could consist of “routing seasonal creeks under paths and roadways is very effective but requires a lot of work and there are a lot of seasonal creeks out there.” 

This is just one of the many solutions to a problem affecting trails all over California that will take time and effort to put in place.  In order to change anything, funding and education are needed to involve everyone in this issue and create better awareness in our community to avoid irreversible damage to a place loved by many. To change anything, MMWD “could work on increasing and improving their volunteer programs to make a push against these species,” Ginsburg said.