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. 

Save the date for the 10th anniversary of the City Nature Challenge in 2025: April 25–28! 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

Making an observation using the iNaturalist app

Participating in the City Nature Challenge is easy!

  1. Download the free iNaturalist app and make an account.
  2. April 25 - April 28, 2025, 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).
  3. Upload your observations to share with the iNaturalist community. They will automatically be added to our San Francisco Bay Area City Nature Challenge project!
  4. Learn more as your finds get identified!



Special thanks to our partners


Additional resources

Explore, observe, and document the plants and animals around you—even inside your house!

Woman taking photo of ivy for iNaturalist

You don't need to venture too far from home to find exciting and surprising creatures! Download this PDF to get started.

Bingo card with Bay Area plants and animals

Download this PDF and see if you can find all 25 of these commonly observed Bay Area (plant and animal) neighbors.

iNaturalist logo

Don't have iNat yet? Download the app today and discover how fun (and easy) it is to document biodiversity in your neighborhood.

Join iNaturalist

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.