Celebrating Biodiversity Downtown

San Francisco is a small city. At just 49 square miles, it’s one of the most densely built cities in the country. Yet nature’s biodiversity is there to be found by those who pause long enough to look up and down or peer closely in our parks and at the trees and planters dotted about. That’s just what we did in Downtown San Francisco on a recent sunny Saturday morning, partnering with Enterprise for Youth to celebrate California’s Biodiversity Week (Sept. 7-15) with a nature walk. 

Our group included young people who work with Enterprise’s Climate Career Corps, Nature in the City supporters, and a few out-of-towners from London and Sydney, also cities with stunning nature. Amber Hasselbring, Nature in the City’s executive director, led the walk. Talia Uribe and Peter Nicosia, staff at Enterprise for Youth, joined us, and Carlo Solis, the organization’s chief executive officer, and native San Franciscan, sent us off with an inspired plea to celebrate the city’s natural and cultural history and imagine its thriving, biodiverse future.

Here’s a recap of our route and sightings with a few curious offshoots, in case you want to explore downtown’s biodiversity on your own.

Yerba Buena Gardens

Yerba Buena, or good herb, the name first given to San Francisco by the Spanish, is also a deliciously fragrant plant, a groundcover in the mint family. We entered Yerba Buena Gardens from 3rd Street across from the SF Museum of Modern Art. The planters and beds of the Cho-En Butterfly Garden were full of pollinator plants, many native to our state or from Mediterranean climates similar to California’s. And they were full of pollinators like bees, grass skippers, and dragonflies. We peered closely to see how many different bees we could count, at least five, probably more. Yerba Buena Gardens has much to explore, including the Reflection Garden honoring this area’s indigenous people and the Sister Cities Garden on the upper terrace with plants from many of San Francisco’s 19 sister cities. Who knew we had so many?

Market Street

Tigers on Market Street? Yes! The Western Tiger Swallowtail Butterfly seems to view Market Street as a river canyon as it flies above the London Plane Trees (the Tiger’s larval food plant, aka, where the butterfly lays eggs) lining San Francisco’s most iconic street. This large, striking yellow-and-black butterfly can withstand Market’s Street’s near-constant wind tunnel, which causes many of us humans to hold our hats and seek cover near the buildings or underground.

Speaking of underground, you may have noticed the new canopy structures covering the BART/ MUNI transit stations popping up along the street. Can you imagine living roofs on these structures, covered with plants to provide safe, productive habitat for wildlife like the Western Swallowtail Butterfly? Nature in the City’s Tigers on Market and Living Roofs projects aim to make all this gray infrastructure just a little greener. Our efforts are supported by the Bay Area Rapid Transit District (BART) and City of San Francisco agencies, including SFMTA, SF Public Works, and SF Environment Department.

At the Montgomery Street station, Amber pointed out a bird nesting box nailed to a tree trunk high above our heads. This cavity-type box might attract House Sparrows, House Finches, Chestnut-backed Chickadees, and Black Phoebes.

Battery Bridge

Market Street may seem like a river canyon to butterflies, but it’s still a cacophony of traffic sounds to talk over and vehicles to navigate. We all safely cross Market–whoosh!–and pause to catch our breath on Battery Bridge at the base of Bush Street. Just a few years ago, Battery Bridge was Battery Street. It was closed to cars during the pandemic to create an outdoor gathering place, and then permanently converted to a pedestrian plaza in 2022. The plaza doesn’t sport a whole lot of biodiversity–the planters contain mainly introduced, low-maintenance ornamentals, and nearby London Plane trees are planted all along Market Street. But the sweeping street mural painted by Mission neighborhood artist Claudio Talavera-Ballón, titled Estero en Moviemiento, represents Drake’s Bay and might give you a sense of being in the natural beauty of Point Reyes National Seashore (watch video about the artist and mural here).

Maritime Plaza and Sue Bierman Park

Maritime Plaza and Sue Bierman Park combine California native plants and introduced species to create a densely-layered green space with mature, fifty-foot- tall Lombardy Poplar trees in the shadow of the vertically looming Embarcadero Center towers. These two parks form the northern border of San Francisco’s peninsula, centrally located along the Pacific Flyway, so this diversity of plants and trees can house an astonishing number of migrating and resident birds and insects. On this park visit, we are rewarded with a Western Tiger Swallowtail butterfly floating amongst the treetops and shrubs, laying her eggs on the underside of various leaves, Amber noted after carefully watching the butterfly’s behavior. “How many eggs?”, someone asked. An excellent question to which we did not know the right answer. We looked up the answer: up to a hundred in her two-week lifespan. We can only hope that her eggs hatch into caterpillars that find enough to eat before they pupate, as they prepare to undergo metamorphosis to become butterflies. (There’s a ton of science packed into that one sentence that we can’t go into here. But this video will refresh your memory about the butterfly life cycle.)

Embarcadero Plaza

Before crossing back over Market Street, we had to walk through Embarcadero Plaza, where Market ends (the name was changed from Justin Herman Plaza in 2017 after determining that Herman’s redevelopment work had particularly devastating impacts on African American and Japanese American residents). This expanse of concrete and brick surrounding the brutalist-style Vaillancourt Fountain and Sue Bierman Park directly to the north (together 5 acres of public land) is just begging for more biodiversity and general greening to create a space that is truly healthy for nature and people. What ideas do you have to complement the plaza’s existing Palm, Gingko, and Chinese elm trees?

Salesforce Park

A quick jaunt down Market Street while focusing up in the tree canopies aiming to eye another Tiger Swallowtail butterfly, we head over to Salesforce Park, the 5.4 acre public greenspace atop the Salesforce Transit Center. Amazingly, the city street sounds don’t make it up to this peaceful park of plants from around the world, fountains, benches, and event and performance spaces. Four stories above the new Transit Center, we can’t help wondering about the weight of the soil and the plants themselves. Our iconic Coast redwoods, one of California’s state trees and the tallest tree in the world, can weigh over a million pounds in its native habitat. 

First opened in 2018, then closed for repairs for nearly a year, the Salesforce Transit Center speaks to San Francisco’s aspiration to be a beacon of public transportation for the region and state…at least, as described in this promotional video. While not all plans have yet been realized, it’s worth checking out the public art installations. The Secret Garden floor, located at street level in the Grand Hall, was created by local artist Julie Chang and celebrates the diversity of San Francisco’s natural and cultural history and may evoke a sense of the Transit Center as a Victorian greenhouse. And back to the 4th-floor gardens, the seemingly random flow of the Bus Fountain, by Ned Kahn, intrigued one person on our walk who didn’t realize the water spouts are activated by the buses moving in the Transit Center below.

A respite from the bustle of SOMA, the Salesforce Park has excellent interpretive signs and offers free, monthly guided garden tours (4th Wednesday of the month, 10-11:30 AM) and birding walks (in partnership with Golden Gate Bird Alliance, 1st Wednesday of the month, 8-9 AM; see calendar for all events). Or grab a few friends and follow this official garden guide or this excellent walking tour from SF Trees.

Offshoots

POPOS

Along and beyond our route, you could also explore Privately-Owned Public Open Spaces, aka POPOS, and public art. The city’s 1985 Downtown Plan stipulated that developers provide publicly accessible spaces within, or on top of, their buildings and that they dedicate 1% of the building’s construction budget to public art (later, a contribution to the city’s art fund was added as an option). Many people are surprised that these massive office buildings sport signs welcoming you to their POPOS (in truth, sometimes the signs are well-hidden). Some POPOS are associated with cafes, and some provide restrooms, but all are meant to offer a respite from the hustle and bustle of downtown streets. Read more about POPOS and public art here and explore using this map (some POPOS may not be open due to construction or vacancy).

Transamerica Pyramid

The renovations to the iconic Transamerica Pyramid, roughly in honor of its 50th anniversary, include carefully preserving an existing Coast Redwood grove of nearly 50 trees and adding new Eastern Redbud trees. The Redwood Park beneath the pyramid is beautifully landscaped with shade-loving ferns, rhododendrons, and what looked like irises.  Also, public art exhibitions are planned for the park, “... celebrating innovation and creativity across the arts and sciences.” The current exhibit  by Claude and Françoise-Xavier Lalanne, features 25 animal sculptures set among the trees and fountain, will run into early 2025 and is worth a visit.

San Francisco Bay

Those interested in marine biodiversity might want to walk down to the Bay just south of the Ferry Building. Sometimes the bird watching is good here, though even more interesting may be what’s happening underwater. Near The Agricultural Building and Pier 14 is one of three sites along the Bay where SF Port and the Smithsonian Institution are experimenting with a Living Seawall, textured seawall tiles that allow marine critters, seaweed, and plants to attach. The idea is to create a more natural green infrastructure, in contrast to the gray infrastructure of most seawalls. Check out this KneeDeep Times article, Who’s on first?, to learn more about the experiment and its findings so far. This experiment is an example of a nature-based solution that SF Port is considering in its Waterfront Resilience Plan. Can you imagine other nature-based solutions for the Embarcadero to address sea level rise and storm surges due to climate change?

We hope you enjoy strolling downtown amidst biodiversity and public art in San Francisco’s expansive parks, POPOS, tree-lined streets, and plazas. Tigers, Dragons…and so much more to discover!

Text and photos by Helen J. Doyle, NTC Advisory Council member