San Diego is renowned as a biodiversity hot spot, but its reputation became official when the region placed among the top three regions in the City Nature Challenge, an international contest to tally plant and wildlife sightings over a four-day period.

The event, which ran April 27-30, enlisted 17,329 outdoor enthusiasts from 68 cities in the Americas, Europe and Asia, to capture images of local flora and fauna, according to the website for the app iNaturalist, which participants used to upload their photos and data.

Together, they logged 441,888 nature observations, and experts in botany, herpetology, entomology and other disciplines confirmed identifications for those findings.

With 33,448 observations of 2,946 different species, San Diego County came in third place among those locales, after San Francisco Bay Area and the Dallas/Fort Worth region for sheer numbers of reports, and following the Bay Area and Houston for total species.


San Diego placed second for its total number of participants, as 1,211 nature lovers scoured their neighborhoods for flora and fauna, just behind San Francisco. And the San Diego Natural History Museum, which coordinated local efforts, gained its own distinction when its botany curator, Jon Rebman, became one of the top identifiers, confirming more than 10,000 species observations.

Although nature counts such as the Audubon Christmas Bird Count have traditions dating back more than a century, current technology enables wildlife watchers, amateur naturalists and professional scientists to collaborate on an unprecedented scale in an event such as the City Nature Challenge, said Bradford Hollingsworth, curator of herpetology for the San Diego Natural History Museum.

“I call this a watershed moment for me, this challenge, where mobilizing more than 1,200 people to make more than 33,000 observations could only happen with the advent of digital photography, GPS and a social platform like iNaturalist,” he said.

A lesser goldfinch, photographed in Poway as part of the City Nature Challene (Bradford Hollingsworth )


Despite the word “city” in its name, the challenge allows competing areas to define their regions based on combined natural resources. In San Diego, officials felt that included both the city itself and surrounding communities and municipalities.

“We found that San Diego County best represents San Diego areas where people like to go out and enjoy nature and explore,” Hollingsworth said.

That outdoorsy bent in San Diego civic life made it easier to recruit participants for the contest, he said. The museum conducted three dozen planning meetings and trained over 200 people to use iNaturalist. And they had ample help drumming up support.

“For San Diego, we’re very lucky in that we have a whole host of nature-loving organizations, from the docents of Torrey Pines, to the Friends of Rose Canyon,” he said.


Among those, certain experienced nature fans acted as super-observers, with a handful of people contributing about half of the observations submitted.

One of those was Jay Keller, a financial services manager from Tierra Santa, who has made a hobby of photographing local plants and wildlife and sharing those images online. Although he was only able to dedicate one full day to the count, Keller uploaded 550 observations and a little over 400 species. His most exciting finds, he said, included a striped racer and endangered San Diego mesa mint plant.

“In the last few years, I have become very interested in botany,” he said. “Even within plants I tried to focus on rarer species that other people wouldn’t know where to find or how to look for. My goal was to contribute as many unique species to the count as possible.”

The region’s celebrated biodiversity stems from the range of habitats it encompasses, from coastal kelp forests to desert cactus gardens. The nature challenge touched on all of those, Hollingsworth said.


“Everything from Imperial Beach to Anza-Borrego, up to Oceanside, out to places like Campo,” he said.

Observations included photos of rare plants, to tide pool life, to a snake devouring a lizard, Hollingsworth said. The event also included the “Balboa Park BioBlitz” from Friday to Saturday, which contributed 2,346 observations of 590 species to the regional count.

A ring-neck snake, photographed in Balboa Park during the City Nature Challenge (Bradford Hollingsworth )

The City Nature Challenge started in 2016, when the Natural History Museum of Los Angeles County and California Academy of Sciences created the contest to harness citizen science to explore local ecosystems.


It began with a competition between just two cities — Los Angeles and San Francisco — and grew to 16 cities throughout the U.S. in 2017. This year, it expanded across the globe, and more than tripled the number of wildlife and plant sightings reported.

Organizers hope the momentum will continue to build next year, as participants experience the thrill of discovery.

“If you have a plant or animal that’s out in nature, you can upload it, and experts on the platform will help you identify it to the species level,” Hollingsworth said. “So by putting your pictures on iNaturalist, you get the return of learning something about what you’re posting.”


deborah.brennan@sduniontribune.com Twitter@deborahsbrennan