City Nature Challenge records 2.4 million wildlife observations from more than 83,000 participants in a single weekend

SAN FRANCISCO, CA (May 6, 2024) — Now in its ninth year, the annual City Nature Challenge (CNC) global bioblitz has concluded, yielding more than 2,400,000 wildlife observations for another record-breaking year. Over the four-day event, held between April 26-29, more than 83,000 people across six continents used the free mobile app iNaturalist to participate however they could—including attending community wildlife surveys and observing species in their own homes—to document the wondrous diversity of wild plants, animals, and fungi that share our planet. From observations of critically endangered and elusive species to sightings outside of known species ranges, information collected during the City Nature Challenge underscores the value of community science to track real-time changes in our planet’s biodiversity—especially in urban areas.

Started in 2016 by the California Academy of Sciences and the Natural History Museum of Los Angeles County as a friendly competition between San Francisco and Los Angeles, the City Nature Challenge has expanded to 690 cities around the world. This year’s CNC broke previous observation records, tallying 2,436,844 observations and recording 65,682 species worldwide—including nearly 4,000 rare, endangered, or threatened species. The highest number of observations were tallied in La Paz, Bolivia, where 3,593 participants made more than 165,000 observations during the four-day weekend! Thanks to an incredible network of organizers and participants in India who brought 200 new projects to the global effort, CNC also saw one of the biggest jumps in participation in its nine-year history. This year’s CNC also welcomed participants from nine new countries: Gabon, Kazakhstan, Madagascar, Malawi, Namibia, Philippines, Poland, Slovakia, and Turkey.

“In terms of community science data, these are the four most valuable days of the whole year,” says Alison Young, co-director of Community Science at the Academy and CNC co-founder. “The City Nature Challenge consistently is the week with the greatest number of wildlife observations on iNaturalist out of the year—all of which are free and accessible. From monitoring endangered, common, and invasive species to simply documenting what’s in your own backyard, all of this data contributes to our collective understanding of urban biodiversity and helps conservation managers and decision-makers identify which species and places to protect.”

See below for highlights from the 2024 City Nature Challenge.

By the numbers: San Francisco Bay Area results

• 39,273 total observations submitted to iNaturalist
• 2,552 observers
• 15 average observations per observer
• 3,334 species documented
• Most observed species: California poppy (Eschscholzia californica)

San Francisco Bay Area highlights

Highlights from around the Bay Area include a sighting of a critically threatened and endemic Bay checkerspot butterfly in Santa Clara County, a great blue heron posing by the Golden Gate Bridge, a curious coyote in Golden Gate Park, an invasive American bullfrog showing the current species range in Palo Alto, an endangered San Francisco garter snake in San Mateo County, an unexpected friendship between a California slender salamander and a western forest scorpion in Los Gatos, a silvery blue butterfly in Santa Clara (the same species reintroduced in the Presidio in April), and a colony of sea lions in San Francisco’s Pier 39, which saw a record number of the iconic pinnipeds just last week.

By the numbers: Global results

• 2,436,844 observations submitted to iNaturalist
• 83,528 observers
• 29 average observations per observer
• 65,682 species documented
• Most observed species: Mallard duck (Anas platyrhynchos)

Global highlights

Highlights from around the U.S. include a bobcat caught on a trail camera in Baton Rouge, Louisiana; a rebellious burrowing owl in Scottsdale, Arizona; a grumpy eastern American toad in Erie, Pennsylvania; mating Atlantic horseshoe crabs in Riviera Beach, Florida; and beached by-the-wind sailors on Catalina Island, California. Highlights from around the world include a well-camouflaged leafy sea dragon in Australia, evidence of a Texas tortoise in Mexico’s Chihuahuan Desert, an endemic prickly waterlily in India, a leaping gold-spotted mudskipper in Malaysia, a sassy southern elephant seal in South Africa, a vibrant jumping spider in Hong Kong, a critically endangered elkhorn coral in Panama, a bioluminescent millipede in Canada, a grass snake preying on a European water frog in Germany, the northernmost record of a Eumenes macrops wasp in India’s Western Ghats, and one of just two observations of flying steamer ducks in Argentina’s Tierra del Fuego.

Highlight images and observations can be found here. 

To view all findings from the 2024 City Nature Challenge, visit iNaturalist.org.