Bumble bees (Bombus) are social insects that depend on flowers for their nectar and pollen diet, making them important pollinators of both wild and crop plants. Many bumble bee species have been reported to be in decline, including in California, where ¼ of native species are threatened, some of these having been afforded federal- or candidate status state-level endangered species protection. Threats driving declines of California bumble bees are related to agricultural activities (especially pesticide use), habitat loss to development, and climate change-related ecological disturbance. One obstacle to bumble bee conservation is a lack of standardized data collection and monitoring, which is necessary to characterize population trends and detect declines. The California Bumble Bee Atlas is a community science effort to address this need. In its first two years, 650 participants have submitted more than 10,000 bumble bee observations using a standardized field survey protocol. The project has documented the persistence of many native species, while also detecting range shifts and declines for others. In this talk, we present data from the Atlas, exploring patterns of species diversity and abundance across the state’s diverse ecosystems, with particular focus on the state’s six bumble bee Species of Greatest Conservation Need.