Ecology of the Golden Gate National Recreation Area
The Golden Gate National Recreation Area is a wide-ranging cluster of areas on either side of the Golden Gate Bridge in California. Stretching from Tomales Bay to San Mateo County, visitors can find themselves completely immersed in one of the Recreational Area’s 19 different ecosystems, or within the city boundaries of San Francisco. Across approximately 81,000 acres of land, the Golden Gate National Recreation Area is home to roughly 2,000 wildlife and vegetation species.
North of the Golden Gate Bridge
The northern end of the Golden Gate National Recreation Area is located within the boundaries of Marin County. The dry-temperate climate of this part of California has temperatures averaging around 49 degrees Fahrenheit. Ecosystems feature the mountains of the Marin Headlands, the estuaries of Tomales Bay and Rodeo Beach, and the forest of Muir Woods.
Tomales Bay, located between Point Reyes National Seashore and the mountains of Marin County, is an important habitat for a diversity of species. Composed of mainly seagrass beds, intertidal sand and mud flats, as well as salt and freshwater marshes, the Bay provides food and habitat for the 20,000 shorebirds, seabirds, and waterbirds that winter in the area, as well as commercially important fish species.
A Closer Look: Eelgrass
The seagrass in Tomales Bay, more specifically called eelgrass, is a crucial feature of the bay for many reasons. First, the eelgrass is the perfect spot for fish to hide from bigger fish, birds, and other predators that might eat them. Second, it provides a source of food for the fish, who eat algae, invertebrates, and detritus (dead organic matter), and birds who prey on the fish. Lastly, the eelgrass acts as an ideal nursery for fish to spawn (breed), as it is much safer for young fish to feed and grow. Eelgrass is not only a habitat for fish, as clams, shrimp, snails, and worms can also be found within its layers. Most importantly, the thick coverage of eelgrass acts as a great filtration system by trapping any sediments and pollutants to improve water quality, and it can play an important role in buffering the effects of storms.
Muir Woods National Monument
South of Tomales Bay is Muir Woods National Monument, which is known for its tall redwood trees, Sequoia sempervirens. Muir Woods is what scientists call an old-growth forest, meaning it has survived thousands of years with relatively little disturbance or destruction in its lifetime. Old-growth forests are crucial to maintaining the biodiversity in an area, as they contain long-living species, such as the redwood trees, which are known to live up to 2,200 years old, that have evolved through thousands of years resulting in the creation of complex and strong interactions with each other and the environment. Old-growth forests also play an important role in carbon capture and nutrient cycling in the forest.
The Marin Headlands is a stretch of coast just north of the Golden Gate Bridge. Notable sites in this area include Rodeo Beach and Lagoon, Mount Tamalpais, and the many estuaries and marshes that drain into the Bay.
Rodeo Beach and Lagoon
Part of Marin County, this location is home to many different species such as the endangered tidewater goby and threatened California red-legged frog. Rodeo Lagoon supports many birds, including brown pelicans, gulls, sandpipers, and ducks. It also plays an important role in protecting the area’s coastline from harsh storms.
Mount Tamalpais is also a key feature of the Marin Headlands. Towering over surrounding cities, the mountain known by locals as Mount Tam provides habitat for many plants and animals. Mammals, such as gray foxes, bobcats, coyotes, black- tailed deer, and mountain lions, are often seen on the mountain. More than 750 plant species have been observed on Mount Tam, including wildflowers such as California poppies, lupines, and Douglas irises. Other plant species, such as spotted coralroot and Pacific trillium can also be found here.
USGS scientists have been actively working in the Mount Tamalpais area since 2017, researching the possible 13 species of bats found in the area. The goal of the research is to better understand bat roosting ecology and distribution. Researchers hope to provide the data needed by state and federal management agencies to make informed decisions on how to best conserve the existing populations. In Marin County, researchers observe bats “roosting” – a term used to describe how bats congregate in a certain area and will return to the same area upon hearing a certain signal – and record ultrasonic vocalizations to identify what species are in the area. This research is important, as not much is known about these bats, and will help scientists better understand the threats affecting the animals, including white nose syndrome, a fatal fungal disease that impacts hibernating bats.
South of the Golden Gate Bridge in San Francisco/San Francisco Bay
Despite being a major city, San Francisco also has notable ecological features, including Ocean Beach and the Presidio.
Ocean Beach is one of the major beaches in the Golden Gate National Recreation Area on the coast of San Francisco. Visitors will most often see small shorebirds among the sand, including the threatened western snowy plover. Other birds found around this area are marbled godwits, willets, Heerman’s gulls, terns, and sanderlings.
Ocean Beach also has a common invasive plant known as ice plant, which was first brought to California in the early 1900s as a method to prevent erosion under railroad tracks. However, the ice plant grows easily in coastal California’s Mediterranean climate and is now widespread. It threatens the area’s biodiversity by out-competing native plants for habitat and resources, such as water, nutrients, and light.
The Presidio of San Francisco
The Presidio of San Francisco is home to some of the city’s coyotes. Coyotes returned to the area in 2002; however, the population remains relatively small. Through their interaction with their urban environment, the highly adaptable species gradually becomes conditioned to "urban stimuli” and human presence. Still, Presidio visitors are dissuaded from getting too close to the coyotes.
Many federal agencies and academic institutions in the Bay Area work with the city of San Francisco to monitor these animals and help minimize their interactions with humans. Researchers tag the coyotes, which are then tracked as they move throughout the many parks of the Golden Gate National Recreation Area, including Marin, Golden Gate Park, Lands’ End, and Glen Park. Pups are typically born in spring, and about six to nine months later, many of the pups go out on their own and develop independence from their parents.
South of San Francisco
The southern end of the Golden Gate National Recreation Area spans from South San Francisco throughout San Mateo County.
One feature of this area is Mori Point, the newest addition to the Golden Gate National Recreation Area, which has been an important site for conservation of coastal habitats and has become a center for the regrowth of populations of the threatened California red-legged frog and the endangered San Francisco garter snake.
The San Francisco garter snake has distinguishable and colorful stripes running the length of its body. The snake is only found on the San Francisco peninsula and are often spotted in or around wet habitats, such as freshwater ponds, marshes, and creeks, especially those used by the threatened California red-legged frog. That is because the frog species is the San Francisco garter snake’s main prey.
Phleger Estate, the southernmost park of the Golden Gate National Recreation Area, is notable for its redwood trees which are some of the only ones in San Mateo County. The park offers an ideal moist environment to aid the growth of the giant redwood trees. Among the forest canopies live the gray squirrel and the Sonoma chipmunk, while the California giant salamander and rough-skinned newt are found buried in leaf litter on the forest floor.