10th Anniversary City Nature Challenge records 3.3 million wildlife observations from nearly 103,000 participants

SAN FRANCISCO, CA (May 5, 2025) — The 10th annual City Nature Challenge global bioblitz has concluded, yielding more than 3.3 million wildlife observations for another record-breaking year. Over the four-day event, held between April 25-28, nearly 103,000 people across six continents used the free mobile app iNaturalist to participate in a range of ways—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 in San Francisco and the Natural History Museum of Los Angeles County as a friendly competition, the City Nature Challenge has expanded to 669 cities around the world over the last decade. This year’s Challenge broke previous observation records, tallying 3,310,131 observations and recording 73,765 species worldwide—including 3,338 rare, endangered, or threatened species. The highest number of observations were tallied in La Paz, Bolivia, where 3,292 participants made 148,994 observations during the four-day weekend. Over the last 10 years of City Nature Challenge, community scientists have submitted nearly 13 million observations to iNaturalist.

“I never imagined that this lighthearted battle between San Francisco and Los Angeles would turn into the world’s largest annual biodiversity event,” says Rebecca Johnson, PhD, Director of Community Science at the California Academy of Sciences and City Nature Challenge Co-Founder. “To see over 100,000 people around the world come together to document more than 3.3 million observations—the largest annual census of biodiversity data—shows how powerful community science can be when we pay attention to nature in our own backyards. This record-breaking anniversary shows what’s possible when we work together, and it’s thanks to our local and global organizers that the City Nature Challenge continues to grow year after year.”

See below for highlights from the 2025 City Nature Challenge.

By the numbers: San Francisco Bay Area results

• 50,094 total observations submitted to iNaturalist
• 2,866 observers
• 17 average observations per observer
• 3,930 species documented
• Most observed species: California poppy (Eschscholzia california)

San Francisco Bay Area highlights
This year, the San Francisco Bay Area project held the third highest number of Challenge participants.Highlights from around the Bay Area include an urban coyote sighting on Lombard Street in San Francisco, a variable checkerspot butterfly soaking up sun in Los Gatos, a covey of quail in San Mateo County, thousands of by-the-wind sailors washed up on coastal beaches, a great blue heron preying on a pocket gopher in San Francisco’s Presidio, a bobcat in Point Reyes, one of several deceased gray whales that have stranded on Bay Area beaches this spring, evidence of beaver activity in Solano County, and a California nightsnake in Sonoma County—an observation that confirms a range extension for this species.

By the numbers: Global results

• 3,310,131 observations submitted to iNaturalist
• 102,945 observers
• 73,765 species documented
• Most observed species: Common dandelion (Taraxacum officinale)

Global highlights
Highlights from around the U.S. include an eastern gray squirrel pausing for a drink in Homewood, Alabama; a fluorescing striped bark scorpion in San Antonio, Texas; a tiny white pygmy poppy in Los Angeles, California; a six-spotted fishing spider waiting patiently for a meal in Chapel Hill, North Carolina; a painted bunting bathing in Lewisville, Texas; and a critically endangered round-leaved sundew in Carter County, Tennessee. Highlights from around the world include the first sighting of Phidiana unilineata—a rare, translucent sea slug from India—in over 160 years, two common terns fighting over a meal in Russia, an endangered green sea turtle in Barbados, a curious raccoon in Canada, a mutualistic relationship between a capybara and a cattle tyrant in Brazil, a glowing moon jelly in Germany, a western Australian seahorse, a mongoose devouring a bird in South Africa, a vibrant jolly telamonia spider in Thailand, a Malayan night heron foraging in Taiwan, and a common coral slime in New Zealand.

Highlight images and observations can be found here.

All findings from the 2025 City Nature Challenge can be found here.