A keystone species is an organism that defines and supports an entire ecosystem, filling a vital ecological niche. Without these species, ecosystems would be radically altered or even collapse. This full-color, pocket-sized field guide by best-selling naturalist Collin Varner highlights fifty keystone trees, flowering plants, fruit-bearing plants, marine plants, and fungi found across the Pacific Northwest bioregion. Each entry features clear photography, etymology, descriptions, habitat information, and risks and warnings. This convenient and easy-to-use reference is perfect for walkers, hikers, campers, and beachcombers and important for raising awareness of the need to conserve and protect these vital species. -- back cover.