Matt Ritter, a botany professor at Cal Poly San Luis Obispo, and Michael Kauffmann, a research plant ecologist, have written a new definitive guide to California's 95 native tree species, "California Trees." The authors discuss their field work across the state, from the rare conifers of the Klamath Mountains to the Joshua trees of the Southern California desert. They reveal how citizen science and new mapping techniques are documenting biodiversity hotspots, and how climate change and wildfires are rapidly reshaping California's forests.