Listen to the Story: Restoration ecologist Josiah Clark reveals the quiet battle for diversity in the urban landscape on Yerba Buena Island.
YERBA BUENA ISLAND, the tall rock where the Bay Bridge ducks into a tunnel between San Francisco and Oakland, is home to one of the Bay Area’s most overlooked ecological front lines.
Habitat Potential is a company of restoration ecologists that maintain the native landscape on the island and across San Francisco’s signature parks, including Golden Gate Park and the Presidio.
“Doing environmental work, I mean, it would be so easy to get grim. You know, everything feels kind of hopeless and dismal,” said the company’s founder Josiah Clark at the end of a long work day clearing eucalyptus leaves from a wooded area on Yerba Buena Island. “But I think that there’s enough beauty and productivity and robustness in nature to kind of carry the story through.”
The team identifies nearly every plant they encounter to determine whether it stays or goes. Their work protects native birds and butterflies by making sure their habitats don’t get crowded out by plants that they can’t eat or nest in.
Crew member Blake Sugarman said eucalyptus leaves are especially threatening because they blanket the forest floor and prevent other plants from getting light and air.
“Non-native leaves don’t break down easily because the decomposers they evolved with aren’t here,” said Sugarman. “And we don’t have enough koalas to eat them all.” Clark is a frequent contributor to ecological surveys conducted by the Golden Gate Bird Alliance, the century-old conservation nonprofit dedicated to environmental activism and education in the central Bay Area.
He also contributes to the Cornell Lab of Ornithology, a global network of multidiscipline participants who catalog species and the geographical locations of birds all over the planet. The archive is used for research by Cornell University’s College of Agriculture and Life Sciences.
Doing environmental work, I mean, it would be so easy to get grim… But there’s enough beauty and productivity and robustness in nature to kind of carry the story through.
Josiah Clark, founder of habitat potential
Armed with chainsaws, machetes and rakes, the crew’s work can resemble hand-to-hand combat against invasive species.
“We get to be that mechanism, very much mimicking the disturbance regimes that would have always managed these lands,” said Clark. “Mimicking fire and mimicking wind and mimicking browsing by animals that maybe aren’t here anymore. We’re losing huge parts of our green space to these invasive plants.”
Three hundred years ago, Yerba Buena Island would have been covered with tall grasses and coast live oak trees, seabirds and sea lions. Some of the songbirds evolved with a distinct dialect, like the white-crowned sparrow (nuttalli). Today only a few scrub jays remain, Clark said, and rare plant species, like the California goosefoot, hover on the brink.
Letting invasive plants take over would turn the region into an ecological monoculture of eucalyptus and fennel, Clark said, leaving the landscape prone to catastrophe. He said those conditions contributed to the 1991 Oakland hills firestorm, also called the Tunnel Fire, which killed 25 people and destroyed 1,520 acres and over 2,000 homes. Clark compares the battle against invasive species to similar forces in society.
“Like our civil rights, if we’re not constantly protecting them, constantly holding them up and identifying things, targeting things, having projects, following through, following up, coming back, doing it again. I mean, it’s just how it’s always been,” he said.
That sort of vigilance is needed to keep everything from turning into a monoculture. “And these invasive species that do kind of take and sequester all the resources for themselves,” he said. “This kind of top-down, non-trickle-down-type energy in the ecology that happens in the system. What they say is, in the future, we will really be judged not on what we created, but on what we chose not to destroy.”