The City Nature Challenge (CNC) is a four-day bioblitz where cities around the world compete to see who can record the most wildlife.

Cities are ranked by the total number of observations, the number of species and the number of people making observations. Besides being a fun challenge, CNC is also a great way to engage in community science and help document the biodiversity of our urban areas.

The event takes place using the iNaturalist website and app. Any observation photo, geotagged from anywhere in the seven-county Philadelphia area (Philadelphia, Delaware, Montgomery and Bucks counties in Pennsylvania, and Camden, Gloucester and Burlington counties in New Jersey) and time-stamped during the four days of the event, will count toward Philadelphia’s tally. Follow the Philly area’s progress on the CNC Philly iNaturalist page: City Nature Challenge 2026: Greater Philadelphia Area · iNaturalist

Explore along with the Academy community through our home on iNaturalist, the Academy Naturalists project group!

Visit the CNC Philly home page for detailed instructions on how to participate. This annual event is organized by Natural History Museum of Los Angeles County and California Academy of Sciences.