What is the City Nature Challenge?
Started in 2016 as a competition between San Francisco and Los Angeles, the City Nature Challenge (CNC) has grown into an international event, motivating people around the world to find and document wildlife in and around their cities, using biodiversity recording apps and platforms like iNaturalist. Run by the Community Science teams at the California Academy of Sciences and the Natural History Museum of Los Angeles County, the CNC is an annual four-day global urban bioblitz at the end of April, where cities are in a collaboration-meets-friendly-competition to see not only what can be accomplished when we all work toward a common goal, but also which city can gather the most observations of nature, find the most species, and engage the most people in the event.
The 2023 City Nature Challenge will be April 28 – May 1. There are 485 cities across 46 countries taking part! Participating is easy: just use iNaturalist to make and share observations of wild plants and animals in any of the nine Bay Area counties. Be sure to check back here as well for information about City Nature Challenge events happening throughout the Bay Area.
How to Participate

Participating in the City Nature Challenge is easy!
- Download the free iNaturalist app and make an account.
- April 28 - May 1, take photos of WILD plants and animals anywhere in the nine Bay Area Counties (San Francisco, San Mateo, Santa Clara, Alameda, Contra Costa, Solano, Napa, Sonoma, Marin).
- Upload your observations to share with the iNaturalist community. They will automatically be added to our San Francisco Bay Area City Nature Challenge project!
- Learn more as your finds get identified!
Bay Area CNC Events
Join an event for the City Nature Challenge to learn more our local species, get hands-on help using iNaturalist, and meet other people interested in nature! Click on the links to learn more and to register if needed. All events are in-person unless noted and will be hosted in English unless noted. Be sure to check back as we'll be adding more events!
Tuesday, April 25
- Virtual (on Zoom) 6-7PM: Introduction to City Nature Challenge & iNaturalist | Hosted by the California Academy of Sciences
Friday, April 28
- Half Moon Bay 10AM-2PM: Pillar Point Bluff, Reef, and Harbor Bioblitz | Hosted by the California Academy of Sciences
- Kenwood 11AM-1:30PM: Sugarloaf Ridge State Park Butterfly pavilion followed by a hike | Hosted by Sonoma Ecology Center
- Berkeley 5-7PM: Aquatic Park Nature Observation Walk | Hosted by Friends of Five Creeks
- Kenwood 6-7:30PM: Sugarloaf Ridge State Park Introduction to iNaturalist & BioBlitz | Hosted by Sonoma Ecology Center
Saturday, April 29
- Winters 8AM-3PM: UC Davis Stebbins Cold Canyon Natural Reserve Bioblitz | Hosted by Friends of Stebbins Cold Canyon Reserve & the UC Davis Natural Reserve System
- Fairfax 9-11AM: Wall Property Bioblitz | Hosted by Fairfax Open Space Committee
- Morgan Hill 9AM-12PM: Little Uvas Open Space Preserve Bioblitz | Hosted by Santa Clara Valley Open Space Authority
- Redwood City 9AM-2PM: Edgewood Park & Natural Preserve Bioblitz | Hosted by San Mateo County Parks
- East Palo Alto 9:30-11:30AM: Ravenswood Open Space Preserve Nature Walk in English & Spanish | Hosted by Latino Outdoors SF Bay Area
- San Francisco 9:30AM-12:30PM: McLaren Park Bioblitz | Hosted by the California Academy of Sciences
- Fairfax 10AM-12PM: California Bumblee Bee Atlas & Bioblitz at Sky Oaks Watershed HQ | Hosted by One Tam, CDFW, Xerces Society
- Castro Valley 10AM-12:30PM: Lake Chabot Bioblitz | Hosted by Wholly H20 & East Bay Municipal Utility District
- Kenwood 11AM-1:30PM: Sugarloaf Ridge State Park Senderos de Mariposas (Butterfly pavilion followed by a hike) in Spanish | Hosted by Sonoma Ecology Center
- Santa Rosa 11AM-3PM: Pepperwood Preserve Wildlife Festival: Bioblitz Nature Walks in English & Spanish | Hosted by Pepperwood
- San Francisco 12-3PM: Golden Gate Heights Bioblitz | Hosted by Nature in the City
- Kenwood 3-4:30PM: Sugarloaf Ridge State Park Short, Accessible Wildflower Walk | Hosted by Sonoma Ecology Center
Sunday, April 30
- Kenwood 8AM: Sugarloaf Ridge State Park BirdBlitz | Hosted by Sonoma Ecology Center
- San Jose 9-11AM: Almaden Quicksilver Mockingbird Hill Bioblitz | Hosted by Keep Coyote Creek Beautiful and BioBlitz Club
- San Francisco 9AM-1PM: Palou Phelps Park & Pier 94 Bioblitz | Hosted by CNPS Yerba Buena Chapter
- San Geronimo 10AM-1PM: San Geronimo Club House Bioblitz | Hosted by the Trust for Public Land
- Oakland 10AM-2PM: Lake Merritt Bioblitz | Hosted by the Rotary Nature Center, the Oakland Museum of California, Insect Sciences Museum of California
- Kenwood 11AM-1:30PM: Sugarloaf Ridge State Park Butterfly pavilion followed by a hike | Hosted by Sonoma Ecology Center
- Kenwood 1-2:30PM: Sugarloaf Ridge State Park Creek Insects | Hosted by Sonoma Ecology Center
Monday, May 1
- Kenwood 11AM-1:30PM: Sugarloaf Ridge State Park Butterfly pavilion followed by a hike | Hosted by Sonoma Ecology Center
- Albany 6-7PM: Albany Hill Nature Observation Walk | Hosted by Friends of Five Creeks
- Kenwood 8-9:30PM: Sugarloaf Ridge State Park Dusk Soundscape | Hosted by Sonoma Ecology Center
Tuesday, May 2
- San Jose 6-9PM: South Bay ID Party at the Willow Glen Branch Library | Hosted by Keep Coyote Creek Beautiful & BioBlitz Club
Special thanks to our partners
From getting the word out to hosting events, the Academy's Bay Area partners make City Nature Challenge the inspiring, empowering, and fun 4-day nature bioblitz that it is—and we are incredibly grateful. Click the links below to learn more about each group.
California Native Plant Society | California Lichen Society | Latino Outdoors | California State Parks: Candlestick Point SRA | Bay Nature | San Francisco Department of the Environment | Nature in the City | Presidio Trust | Golden Gate Audubon Society | California Native Plant Society Yerba Buena Chapter | Sutro Stewards | Golden Gate National Recreation Area | San Mateo County Parks | Sequoia Audubon Society | Bioblitz.club | East Bay Regional Parks | California Center for Natural History | Community for Lake Merritt | Oakland Zoo | Oakland Museum of California | Wholly H2o | One Tam | Marin Municipal Water District | Marin County Parks | Sonoma Ecology Center | Sonoma County Parks | Pepperwood Preserve | Napa County RCD | Saved by Nature | Keep Coyote Creek Beautiful | Santa Clara Valley Audubon Society | Grassroots Ecology
Additional resources
Explore, observe, and document the plants and animals around you—even inside your house!
You don't need to venture too far from home to find exciting and surprising creatures! Download this PDF to get started.
Download this PDF and see if you can find all 25 of these commonly observed Bay Area (plant and animal) neighbors.
Don't have iNat yet? Download the app today and discover how fun (and easy) it is to document biodiversity in your neighborhood.
Have questions about the City Nature Challenge? Visit our Frequently Asked Questions page to find some answers!
The work we do utilizes iNaturalist to make biodiversity observations while building community around nature. It's a community-powered website and app that makes it easy to upload and share your observations in the field and to get help from other users with flora and fauna IDs.
Have questions about our community science programs? Want to get involved? Email us at communityscience@calacademy.org.