Although California is often regarded as a regional civilization within the United States of America, this article argues that California justifies being considered a major civilization in itself, indeed the only genuinely 21stcentury civilization, if only because of its top ranking among world economies. The article traces the varied facets of California natural and social history to show the overriding importance of biodiversity as a perennially unifying theme for an understanding of that civilization, and it confronts the varied challenges to (...) this biodiversity that constitute more recent California history and politics. (shrink)