Jon Christensen writes: "A Hollywood drama of butterfly extirpation and persistence over a century of urbanization," reads the headline on a recent scientific study in the Journal of Insect Conservation. The story that unfolds offers glimmers of hope for the rich biological diversity that lives amongst us in Los Angeles.
For two years, Tim Bonebrake and Daniel Cooper systematically surveyed Griffith Park to see which species of butterflies live there today. They spent 71 days across the seasons observing butterflies in six sites around the park. At the same time, they combed through historical field notes and specimen records from 1900 to 1960 to find the species that used to live there.
Their goal was to figure out how one beautiful, iconic slice of biodiversity was affected as a megacity developed around Griffith Park, effectively turning it into an island in an urban ocean. It's a well-known scientific axiom that local populations of species tend to blink out more quickly on islands. This is sometimes called a local extinction or extirpation.
In Griffith Park, 10 native butterfly species, 18 percent of the 55 native butterfly species that once lived in the park, have disappeared without a trace. What surprised Bonebrake, who is an old friend and colleague of mine, is not that so many species went extinct locally, however. It's that so many species survived.
Bonebrake and Cooper even discovered one butterfly thought to have vanished from the park long ago. The wonderfully named cloudy-tailed copper, Lycaena arota nubila, is a critically endangered butterfly that hangs on in a narrow swath of urban southern California. It was first described by local lepidopterist John Adams Comstock in 1922. Adams kept detailed notes on his observations during walks in the park and wrote one of the first field guides to the butterflies of California. Griffith Park was a favorite spot for naturalists in the early 20th century, and their field notes helped Bonebrake and Cooper establish a historical baseline to measure change.
Despite the fact that preserving species has never really been a significant priority for LA's city park system, Bonebrake and Cooper found that many native plants and butterflies have survived in Griffith Park. "Urban parks and open spaces can represent effective and valuable conservation reserve systems even when, as is the case for Griffith Park, conservation initiatives have been minimal or slow to develop," they conclude.
Griffith Park has one important thing going for it--size. In conservation, size matters. At 4,310 acres--almost seven square miles--Griffith Park is a large island of habitat in a sea of city. This makes it an especially important place for urban conservation--a kind of refuge for species that live amongst us, big enough even for one lonely mountain lion to survive, but sheltering hundreds of other, less iconic species too. Because of its size, Griffith Park could serve as an important node in a larger network of habitat fragments throughout the city.
Bonebrake and Cooper call for more explicitly recognizing parks and open spaces containing native shrubland ecosystems like Griffith Park as more than "waste land" within urban areas--even if they are not as big as Griffith Park. We should value these patches of habitat for their "significant natural resources" and develop explicit conservation strategies for these areas, which could help "stem ongoing losses of biodiversity in our increasingly urbanized world," they argue. Then we might "look forward to a possible 'Hollywood ending' for the wildlife of Los Angeles and other urban centers worldwide."
Photos of butterflies in Griffith Park courtesy of Tim Bonebrake. Top to bottom: Cloudy-tailed copper (Lycaena arota nubila), Anise swallowtail (Papilio zelicaon), Behr's metalmark (Apodemia virgulti), Echo azure (Celastrina echo).