City Nature Challenge
4-day global bioblitz run by California Academy of Sciences and Natural History Museum of LA. Cities compete to record the most observations, most species, and engage the most people via iNaturalist. 2024: 2.4M observations, 65,700+ species, 83,000+ participants in 675 cities.
Explicit city-vs-city leaderboard across three categories (observations, species, people). Started 2016 as San Francisco vs Los Angeles rivalry. That origin story is part of the marketing. Cities now have local press coverage of their CNC ranking each year.
Within each city, a local organizing host (museum, park district, nature center) coordinates events, walks, ID workshops. Volunteers help newcomers learn iNaturalist, and species-ID experts work overtime during the 4-day window. Strong city-pride mobilization with hashtags and team meetups.
Pure inter-city competition that doubles as scientific data collection. The 'collaboration-meets-friendly-competition' framing is exactly the spirit BelongHub should catalog. Distinct from the basic iNaturalist usage already mentioned in the exclude list.
Others in the same family
Beat the Street
Free 6-7 week walking and cycling game played across a town. Contactless RFID Beat Boxes are mounted on lamp posts across the playing area; players (children, families, workplaces, voluntary groups) tap cards on boxes to score points. Over 1.9 million participants have played in 5,000+ schools to date.
BiodiverCity Challenge (Alberta)
Regional spin-off of the City Nature Challenge model run by Nature Alberta. Residents in participating Alberta cities/towns use iNaturalist or eBird to log observations during the challenge window. Specifically calibrated for the Leduc-Edmonton-St. Albert corridor.
Walksy / WalkOff (fog-of-war walking games)
Your city map starts under a mist; every step clears fog around your GPS position and reveals streets, parks, and landmarks. Add friends, join/create guilds, fight guild territory wars over city sectors.
City Nature Challenge
Started 2016 as LA-vs-SF friendly competition; now an annual end-of-April 4-day bioblitz where cities compete on most observations, most species, most participants. Using iNaturalist. Run by California Academy of Sciences + Natural History Museum LA.
Capitales Françaises de la Biodiversité
Run by Plante et Cité + Office Français de la Biodiversité. Annual themed competition (2026 theme: nature restoration) where French municipalities document their best biodiversity practices through regional workshops and a national jury.
Beat the Street
Intelligent Health turns a whole town into a 6-week board game. ~60 contactless 'Beat Box' sensors are mounted on lampposts; residents tap an RFID card/fob between boxes (must be within 1 hour) to score points. 1.9-2M players to date across 200+ places; £321.80/adult social value (2025).