Insect conservation in an urban biodiversity hotspot: The San Francisco Bay Area

The San Francisco Bay Area hosts a diverse insect fauna and a dense cluster of urban areas. The high diversity of insects in the Bay Area arises for three primary reasons: its location in the California biotic province, the diverse local environment and the entomologist-area effect. The juxtaposition of high insect diversity and an area intensively used by humans led to the first recorded extinction as well as the first efforts to conserve insects in the United States. Habitat loss due to urbanization, agriculture, and invasive species is largely responsible for local extinctions and reduction in abundance of the remaining species. Invasive species such as the Argentine ant and pathogens causing mortality of oaks and pines are poised to have substantial impacts on the insect fauna of the Bay Area in the near future. Understanding which taxa can or cannot persist in remnant habitat patches within an urban or agricultural matrix, and what management practices would encourage persistence should be a focus of future research. Assessments of population status should be focused on insects at risk of extinction because of their restricted geographic ranges, low vagility, interactions with invasive species, or known reduction in their habitat. Assessments that combine examinations of museum collections, literature, and field surveys might enable determination of the status of many species within the Bay Area. Such an approach might better define the scope and magnitude of the problem of conserving insects in an increasingly urbanized region.