City Nature Challenge, the largest annual biodiversity census in the world, returns for its 11th year of connecting people through local nature and their communities. From participating in organized biodiversity surveys to recording neighborhood wildlife, City Nature Challenge encourages community scientists of all levels to explore their local environment — all while contributing to biodiversity science and conservation.
Identification of photographed species will be crowdsourced through the online community, with results announced on May 13.
How to participate: Photos and sound recordings of any wild plant, animal, fungus, slime mold, or other evidence of life (scat, fur, tracks, shells, etc.) can be uploaded to the iNaturalist app or website, where a global community of naturalists confirms identifications. Wildlife can be found anywhere: homes, neighborhoods, backyards, and beyond.
The Center for Biodiversity and Community Science (CBCS) at the California Academy of Sciences co-leads the Global City Nature Challenge with the Natural History Museum of Los Angeles County. The CBCS team also leads the California Statewide and San Francisco Bay Area Regional organizing.
2026 San Francisco Bay Area Events
Friday, April 24, 2026
9–11 a.m.: Bird Bioblitz at Jack London SHP, Sonoma County hosted in Spanish by Jack London Park Partners and Sonoma Ecology Center, register here.
9 a.m.–1 p.m.: Bioblitz at Yerba Buena Island hosted by the San Francisco Environment Department, register here.
10 a.m.–1 p.m.: Tidepool Bioblitz at Pillar Point, San Mateo County hosted by the California Academy of Sciences, register here.
11 a.m.–4 p.m.: iNaturalist Tutorials at Presidio Field Station hosted by the Presidio Trust and Presidio Field Station, no registration required, learn more here.
1–2:30 p.m.: Bioblitz and Educator-led Hike at Coyote Point Park, San Mateo County hosted by CuriOdyssey, register here.
Saturday, April 25, 2026
9–11:30 a.m.: Bioblitz at Shoreline Lake, Santa Clara County hosted by Grassroots Ecology, register here.
9 a.m.–12 noon: Bioblitz at Fernandez Ranch, Contra Costa County hosted by the John Muir Land Trust, registration not required, address: 1081 Christie Rd, Martinez, CA 94553
9:30 a.m.–4:30 p.m.: Tabling and Bioblitz at the West Valley College Wildflower Show in Santa Clara County, no registration required, learn more here.
10 a.m.–12 noon: Wildflower and Critter Walk at Jepson Prairie Preserve, Solano County hosted by the Solano County Office of Education and the Solano Land Trust, learn more here.
10 a.m.–12:30 p.m.: Bioblitz at Lobos Creek, San Francisco County hosted by Golden Gate National Parks Conservancy, learn more here.
10 a.m.–1 p.m.: Wildflower and Nature Hike at Pepperwood Preserve, Sonoma County hosted by Pepperwood Preserve, register here.
10 a.m.–1 p.m.: Bioblitz at Bon Tempe Lake (Mt. Tamalpais), Marin County hosted by Marin Water, Golden Gate National Parks Conservancy, California State Parks, and San Francisco State University, register here.
10 a.m.–1 p.m.: Bioblitz at Lakeside Park in Lake Merritt, Alameda County hosted by Rotary Nature Center Friends, registration not required.
1–3 p.m.: Bioblitz at Bayview Hill Park, San Francisco County hosted by the California Academy of Sciences and ReImagining San Francisco, register here.
3–5 p.m.: Bioblitz at Sugarloaf Ridge SP, Sonoma County hosted in Spanish by Jack London Park Partners and Sonoma Ecology Center, register here.
Sunday, April 26, 2026
9–11:30 a.m.: Bioblitz at Alum Rock Park, Santa Clara County hosted by Keep Coyote Creek Beautiful, register here.
9 a.m.–12 noon: Bioblitz at Howarth Park, Sonoma County hosted by We Save the World, register here.
9 a.m.–1 p.m.: Bioblitz at Brotherhood Way, San Francisco County hosted by the San Francisco Environment Department, register here.
10 a.m.–12 p.m.: Bioblitz at Pier 94 Salt Marsh Wetlands, San Francisco County hosted by the Golden Gate Bird Alliance, register here.
Post-City Nature Challenge Events
Tuesday, April 28, 2026, 6–9 p.m., City Nature Challenge Identification Party at Sonoma Willow Glen Library, Santa Clara County hosted by Keep Coyote Creek Beautiful, register here.
Thursday, May 7, 2026, 4–6 p.m., City Nature Challenge Identification Party at the California Academy of Sciences hosted by the Center for Biodiversity and Community Science, registration is limited, please email Jessica Carver at jcarver@calacademy.org if you’re interested in attending.