Seven years ago, Andrea Montoya took her grandson to play in Boulder Creek — and her life changed forever. “My husband said, ‘Did you see that structure over there? That’s called a bee house,’” Montoya recalls. Built by local group BeeChicas, it looked like a slanted bookshelf on a pedestal. But instead of books, it was filled with wooden logs drilled with small holes. Montoya had recently retired from her career as a physician assistant because of a rare inflammatory disease, and the bee house sparked her curiosity. “I got immediately drawn to it,” she says. “So I went home that day, sat down and started reading.” She read about native bees, their importance to the environment, and the threats they face. “And as soon as I learned about that, I realized that all they needed was more habitat. That seemed like such a simple fix,” Montoya says. She began to plant native flowers — first in her own backyard, then in her neighborhood. She raised money, enlisted volunteers and led planting...