The Mission blue butterfly (Icaricia icarioides missionensis) is a federally endangered species that occurs in coastal grasslands from Marin through San Mateo Counties in central California. Regionally, the forb-rich coastal grasslands on which Mission blue butterflies depend are decreasing, lost to urban development and the lack of burning or grazing that historically maintained them. Another major threat to Mission blues is an episodic fungal pathogen that kills its primary host plant, particularly in years with wet springs. Recent monitoring data show Mission blue and host plant numbers and distribution declining in GGNRA parklands in San Mateo County. The Mission blue population has gotten so low at Milagra Ridge that it is at risk of extirpation, which would result in the loss of a core meta-population in San Mateo County. Translocating Mission blue adults into enhanced areas is a critical step to build resilience into this system and prevent extirpations of Mission blues in the face of climate change.
The Mission blue butterfly translocation project aims to replicate successful efforts taking place nearby at Twin Peaks in San Francisco. Under this project, Mission blue butterflies will be collected from healthy populations at San Bruno Mountain for translocation to Milagra Ridge. The goal will be to get populations at these sites to robust, self-sustaining levels. This project would be an important step towards recovery of the Mission blue butterfly. This project is a partnership between the National Park Service, Golden Gate National Parks Conservancy, Creekside Center for Earth Observation, San Mateo County Parks, and the U.S. Fish and Wildlife Service.