The darling of famous biologist Paul Ehrlich, the Bay checkerspot butterfly has enjoyed plenty of scientific attention over the years. In fact, since 1960, its population size has probably undergone more observation than that of any other insect. Ehrlich developed the concept of metapopulations by studying the checkerspot, now a conservation paradigm. How ironic that the butterfly's numbers were at record-low levels by the 1980s — and it's been in long-term decline ever since.

Luckily for the Bay checkerspot, its population plunge was observed early on by biologists, earning it a federal Endangered Species Act listing in 1987. But the sensitive butterfly and its native host plants are no match for human development and nonnative plant invasions. Since the U.S. Fish and Wildlife service failed to designate critical habitat for the species after its listing, the Center filed suit and ultimately won more than 23,000 acres of habitat protections for the butterfly. Unfortunately, the agency slashed that protected habitat by 23 percent in August 2008, ignoring the conclusions of its own federal recovery plan as well as the threat of climate change, which reduces food availability for the butterfly's larvae.

Like all butterflies, the Bay checkerspot is extremely vulnerable to pesticides, which contaminate its host plants and poison its larvae. To protect species from toxic chemicals, the Center is challenging the Environmental Protection Agency's registration and authorization-for-use of 46 pesticides in and upstream of habitats for San Francisco Bay Area endangered species, including the Bay checkerspot. We've also released a comprehensive report, Poisoning Our Imperiled Wildlife, detailing the risks posed by pesticides to the checkerspot and other endangered wildlife in the Bay Area. We continue to monitor and oppose harmful chemical pesticide use in California through our Pesticides Reduction Campaign.