San Francisco’s Natural Heritage


Two hundred years ago, you could start walking from any point in San Francisco and within 30 minutes encounter an extraordinary variety of habitats and wildlife. From Ocean Beach to North Beach, the tip of the peninsula was blanketed by great sand dunes with a patchwork of wildflowers and bunchgrasses that provided food for elk, jackrabbits, and other creatures. San Francisco’s grassy hilltops were surrounded by a mosaic of ancient oak and bay laurel woodlands, wet meadows, and coastal chaparral. You would not have needed to carry water on your walk, for every corner of “town” offered a source of clear, sweet water from creeks, ponds, and springs. Creeks flowed into the bay, where unimaginably rich salt marshes provided a year-round abundance of food for people and wildlife alike.

This incredible biodiversity has not disappeared completely. You can still climb the wildflower-studded slopes of McLaren Park and Bernal Hill. You can hear birds call to one another in the coastal scrub of Mount Davidson and Twin Peaks. You can admire hundred-year-old oak trees in Golden Gate and Buena Vista parks. You can hear the rushing water of Islais Creek in Glen Canyon and Lobos Creek in the Presidio.

There are still remnants of grasslands, coast scrub, oak woodlands, stream corridors, freshwater wetlands, and salt marshes throughout San Francisco. Natural areas can be found in well-known parks, such as Golden Gate Park, Twin Peaks, and Lake Merced, as well as in less-frequented neighborhood parks and open spaces. With a little imagination, you can still enjoy a bit of wildness in the city we all love.

Fun Facts About Wild San Francisco!

  • There are more than 350 species of native plants in San Francisco, ranging from seasonal wildflowers like the California poppy to coast live oak trees, which live as long as 300 years.
  • There are 13 species of insectivorous bats that help to limit mosquitoes in the city.
  • The largest mammals native to San Francisco are gray fox and coyotes.
  • The Farallon Islands, part of the City and County of San Francisco, are home to North America’s largest seabird colony outside of Alaska.
  • Fifty-six species of bees can be found in the Presidio alone.
  • San Francisco is the convergence point for northern and southern alligator lizards; both species can be found here.
  • Ninety percent of the shorebirds that migrate along the Pacific Flyway (from Mexico to Alaska) do so within a two-week window at the end of April.
  • The California slender salamander, commonly found under rocks and logs in backyards, is San Francisco’s most common amphibian and possibly the most sedentary, rarely moving more than 10 feet in its lifetime.
  • The only native fish found in San Francisco’s freshwater creeks is the three-spined stickleback.
  • San Francisco’s bedrock is composed of sand, chert, basalt, greywacke, and serpentine, California’s state rock.
  • Each year, more than 50,000 volunteer hours are devoted to habitat restoration in San Francisco.
  • Until 1847, San Francisco was called Yerba Buena, after a native mint that still grows in natural areas around town.
  • Slugs are hermaphrodites, which means they have both male and female sex organs, allowing them to self-fertilize.
  • All the ants on the planet, taken together, have a biomass greater than that of humans.
  • Bumblebees can detach their wings from their wing muscles to raise their body temperature.
  • Kestrels and other raptors have evolved with the ability to see ultraviolet light. This allows them to track rodents on “urine highways” as they scurry through San Francisco grasslands.
  • At 927 feet, Mount Davidson is the highest peak in the city.
  • Natural areas comprise only about 3 percent of the City and County of San Francisco.
  • San Francisco is home to nearly 20 rare and endangered plants.
  • San Francisco and the Bay Area are biodiversity “hot spots”.
  • For the first time in history, more humans live in cities than in the countryside.
  • There are more than 30 miles of designated trails in San Francisco Recreation and Park Department natural areas.
  • Only six gardeners are assigned to the Natural Areas Program.
  • Some spiders are able to produce web strands that are five times stronger than steel.
  • The Natural Areas Program maintains both native and existing exotic trees.
  • A butterfly can flap its wings 80 to 120 times in 10 seconds. In the same time period, a bee can flap its wings 2,500 times, and a mosquito can flap its wings 10,000 times!


Pollution, habitat loss and fragmentation, and invasive species all make it difficult for native plants and animals to survive in the city. In recent years, invasive species have become a particular problem across the country and around the world, threatening landscapes from parks, farmlands, and urban open spaces to rivers, lakes, and even San Francisco Bay.

“Invasive species” is the term used for species that are introduced to an area they did not previously inhabit and that spread quickly, displacing the native species. Of the thousands of introduced plant species, only a handful are invasive and destructive to San Francisco’s natural heritage. These species reproduce rapidly, unchecked by the predators and pests that kept them in ecological balance at home, and can replace the rich and diverse local flora with a monoculture consisting of only a single species. When this happens, many of the insects, birds, and other animal species that depend on the diversity of native plants for food, shelter, and reproduction decline rapidly or even become extinct. For more information about invasive species, see theCalifornia Invasive Plant Council website.

Academic researchers are beginning to realize that urban parks and open spaces play an important role in supporting certain species, particularly pollinators, whose populations are dwindling worldwide. In recent years, researchers from San Francisco State University’s Biology Department have conducted several studies that focused on species diversity and abundance in the city’s natural areas: two on native bee species, one on bats, and one on native and invasive ants. All four studies concluded that natural areas have great potential as urban refuges, particularly if managed to promote species diversity.

Working alongside community stewards and volunteers, the Natural Areas Program protects our remaining wildlands by controlling the spread of invasive plants. For more information on how to volunteer to protect San Francisco’s natural areas, see our Volunteer Opportunities page.