Biological diversity is considered one of today's most urgent environmental concerns, yet the term was first coined only twenty-five years ago. Why did the concept of biological diversity so quickly capture public attention and emerge as a banner issue for the environmental movement? In this book, Timothy Farnham explores for the first time the historical roots of biological diversity, tracing the evolution of the term as well as the history of the conservation traditions that contributed to its rapid acceptance and popularity. Biological diversity is understood today as consisting of three components - species diversity, genetic diversity, and ecosystem diversity. Farnham finds that these three tiers coincided with three earlier, disparate conservation traditions that converged when the cause of preserving biological diversity was articulated. He tells the stories of these different historical foundations, recounts how the term came into the environmental lexicon, and shows how the evolution of the idea of biological diversity reflects an evolution of American attitudes toward the natural world.