The archive · Public & Social · Marketing decision · 2016–2024
City Nature Challenge: LA vs SF photo rivalry grows into a 690-city wildlife census
LA and San Francisco museums turned their city rivalry into a wildlife photo contest — by 2024, 690 cities logged 2.4M observations in four days.
California Academy of Sciences · Natural History Museum of Los Angeles County
What it had to solve
Two natural history institutions wanted people to notice that cities are full of wildlife — and to gather real biodiversity data cheaply. They also had a natural asset: the long-running San Francisco–Los Angeles rivalry over sports and culture, plus the first-ever Citizen Science Day in 2016 to hang the event on.
How it works
The City Nature Challenge began in 2016 as a one-week contest between Los Angeles County and the San Francisco Bay Area, dreamed up by the citizen-science teams at the Natural History Museum of Los Angeles County and the California Academy of Sciences. Any resident could join by photographing wild plants, animals or signs of life and uploading the observation to iNaturalist; domesticated pets and zoo animals did not count.
The rules deliberately made science out of everyday looking: a picture taken on a sidewalk or in a schoolyard was as valid as one from a park, because each observation carried location and date data. Organizers Lila Higgins and Alison Young told the Los Angeles Times that the point was to mobilise thousands of eyes — the only practical way to map where species actually live in cities, and to catch surprises such as sea slugs appearing outside their known range.
The format scaled because other cities wanted in: what began as a two-city duel is now an annual four-day global bioblitz in late April run by the same two institutions. In 2024 its ninth year, 690 cities on six continents took part, with 83,528 observers recording 2,436,844 observations of 65,682 species — roughly 4,000 of them rare, endangered or threatened — in a single weekend.
Why it lands
- It borrowed the energy of sports rivalry: beating the other city gave an act of nature-watching a story people wanted to win.
- The barrier to entry was nearly zero — any phone camera and any patch of city counted, so experts and beginners competed on equal footing.
- The same action produced both play and data: photos with location and date were published openly and shared with global biodiversity databases.
- It scaled through an organizer network instead of a marketing budget, letting two museums turn local pride into a worldwide event.
What it did
The first duel of about 1,000 observers grew into an international event: in 2024, 690 cities on six continents took part, and 83,528 observers logged 2,436,844 observations of 65,682 species, including nearly 4,000 rare, endangered or threatened ones. La Paz, Bolivia alone contributed more than 165,000 observations, and organizers call the four-day window the most valuable community-science data weekend of the year.
What you can take
Competition is the engine: a low-stakes city rivalry multiplied participation, while a strict shared rulebook — wild species, photos, open data — kept the game scientific.
Since then
The City Nature Challenge kept breaking its own records: by 2024 it spanned 690 cities on six continents, and the four-day event became the single biggest burst of wildlife observations on iNaturalist each year. Museums say the resulting open data helps conservation managers and decision-makers track rare, invasive and shifting species, and the event keeps adding new countries — nine joined in 2024 alone. What started as a joke about the Giants and the Dodgers now frames urban biodiversity as something citizens can measure themselves.
Sources
- Q&A: L.A. takes on San Francisco in the first City Nature Challenge
- SF vs. LA: citizen scientists race to document local biodiversity in statewide showdown starting April 14
- City Nature Challenge records 2.4 million wildlife observations from more than 83,000 participants in a single weekend
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