Giants-Dodgers? Niners-Rams? Steph-LeBron? Sorry, the best SF-LA rivalry is for the birds. And the flowers, bees, slime molds, and tons of other creatures in our north-south urban landscapes.
This weekend marks the 10th anniversary of the City Nature Challenge, a crowdsourced biodiversity survey that encourages anyone with a smartphone and free app like iNaturalist to explore their local environment and share observations.
The challenge began in 2016 as just a California thing — a friendly throwdown between LA’s Natural History Museum and SF’s own California Academy of Sciences. Each institution organized a weekend hunt for local plants, animals, and other organisms, with bragging rights for the most observations and participants. That year, LA won, with minimal harm done.
“There was some trash talking, but it was all good-natured,” notes Rebecca Johnson, director of the Center for Biodiversity and Community Science at the Cal Academy. (As far as we know, Johnson didn’t put “good-natured” in air quotes.)
Other cities saw the fun LA and SF were having and wanted to take part. Today the challenge is worldwide, with more than 600 cities across more than 50 countries contributing to the largest citizen-science data upload of the year.
This global census is even more important now that the US government is erasing environmental data and decimating the agencies that collect it. Recognizing climate change and taking measures to mitigate the impact requires good tracking of animal and plant populations.
Update, 5/5/25: The weekend results are in. There were more than 3.3 million reports from nearly 103,000 people worldwide, recording nearly 74,000 species. The Bay Area had a total of 2,866 citizen scientists contributing, putting it in third place globally for participation. La Paz, Bolivia was first.
In San Francisco, these data even provide a metaphor for the city’s uneven recovery. The city’s green spaces in the outlying neighborhoods are thriving and nature is rebounding, even as the downtown core suffers.
In past surveys, people have spotted the western saltmarsh woodlouse (Littorophiloscia richardsonae) in India Basin, the ornate tiger moth (Apantesis ornata) in Glen Canyon Park, and the variable checkerspot butterfly (Euphydryas chalcedona) in the Presidio, Tank Hill, and Twin Peaks.
“Almost every year, people find endangered, threatened species in cities, and someone will find a new-to-science species,” Johnson tells The Frisc. “These data are a way to inventory and have more eyes looking.”
Frog renewals, butterfly bordellos
The biggest reward of the annual challenge is a greater understanding of the shifts in biodiversity.
For example, birds like the spotted towhee (Pipilo maculatus) and dark-eyed Junco (Junco hyemalis) benefited from the violent 2023 storms that felled hundreds of trees across SF. These ground-dwelling birds need a denser understory, as do the insects that serve as their food (spittlebugs). Pollinators (bees and butterflies) benefit too.
The ongoing restoration of the Presidio is also a gift to the city’s biodiversity. Now prevalent around town, SF’s coyote renaissance began there, along with a great horned owl comeback.
Springs that seep through the serpentinite, California’s state rock, beneath Inspiration Point have created a pond where marshland plants grow. It’s perfect habitat for the return of the the Sierran chorus frog (Pseudacris sierra) and forktail damselfly (Ischnura gemina). The chorus frog has also rebounded in other restored natural areas like Islais Creek.
This weekend’s “bioblitz” is also peak time for SF wildflowers. Among the best spots are India Basin, Hilltop Park, Twin Peaks, McLaren Park, and Golden Gate Park, where you’ll find plenty of forget-me-nots, Douglas iris, Fremont’s phacelia, blackberry flowers, and California poppies. (Pro tip: Strawberry Hill, in the middle of Stow Lake, is a special place for flowers and butterflies to mingle.)
Other species might be under foot or growing on a bench carved from a log, like the common sunburst lichen (Xanthoria parietina).
The Cal Academy’s Johnson says the most spotted species every year around the globe are the mallard duck and the honey bee — species that have adapted to being around humans — just like Canada geese, dandelions, sparrows, robins, pigeons, and countless others. (The data also show a northern hemisphere bias, since it’s spring here and flora and fauna are coming out.)
Locally, the most spotted species are the California poppy (Eschscholzia californica), the state flower, western blue-eyed grass (Sisyrinchium bellum) and western bush monkeyflower (Diplacus aurantiacus), known for its sticky orange blooms.
More than 7 million observations are expected — the single biggest event on iNaturalist. But what’s really great about the City Nature Challenge is how it unifies people, says Johnson. “It’s so cool that people all over the world are getting out where they live, noticing nature, taking pictures, and sharing. When things feel so uncertain, this is a chance to take a breather.”
The challenge is also an early weekend series between LA and SF, only not between the Giants and Dodgers. There’s no pitching duel — just a battle of the amateur scientists. The “contest” runs through 11:59 PM Monday, and results will be announced on May 5. But the tabulation is less a box score and more an account of what persists despite politics, rivalries, and even big fires.
It’s often said that nature bats last, and in this challenge it’s the big winner.
Correction, 4/29/25: This story originally reported the wrong date for the announcement of the challenge’s results.