When UC ANR conservation biologist Adina Merenlender launched the California Naturalist program in 2012, she was looking to do more than just educate people. She wanted to build a community — inspired to be stewards of the natural world and to push for the resources and policies needed to defend the state's threatened biodiversity.

“Success to me,” Merenlender said on an afternoon walk through the oak woodlands of the Hopland Research and Extension...