As pollinators of native plants, bumble bees play a key role in structuring ecosystems. They also deliver the ecosystem service of pollination to many crops, providing a substantial monetary benefit to US agriculture. These bees are negatively impacted by agriculture, climate change, and habitat loss, with one-quarter of species native to North America now threatened with extinction. California is a bee biodiversity hotspot, but systematic surveys to document bumble bees have never been performed. Launched in 2022, the California Bumble Bee Atlas is a community science collaboration filling this gap, with volunteers gathering non-lethal survey data around the state, identifying species in need of conservation, and assisting partners with recovery efforts. This talk will describe the ecology and conservation of bumble bees, as well as the first year of results from the California Bumble Bee Atlas community science project.