Book excerpt: Edited and written by Harvard Medical School physicians Eric Chivian and Aaron Bernstein, Sustaining Life presents a comprehensive--and sobering--view of how human medicines, biomedical research, the emergence and spread of infectious diseases, and the production of food, both on land and in the oceans, depend on on the earth's disappearaing biodiversity. With a foreword by E.O. Wilson and a prologue by Kofi Annan, and more than 200 poignant color illustrations, Sustaining Life contributes essential perspective to the debate over how humans affect biodiversity and a compelling demonstration of the human health costs.