In 1978, in his last years of residency in psychiatry at Mass General Hospital, Eric Chivian decided to do something bold. Encouraged by Australian physician, Helen Caldicott, who spoke of the medical dangers of the nuclear fuel cycle and of nuclear power, in particular, he decided to restart an old medical organization—Physicians for Social Responsibility. Their opening public meeting was scheduled, coincidentally, on the same day of the partial-core meltdown at the Three Mile Island nuclear power plant in Pennsylvania. Within weeks, Physicians for Social Responsibility became a national organization with thousands of new members as a result.  While many older physicians within the organization were more concerned with nuclear war, others were focused on the use of nuclear power. Both were interested in disseminating information about what they believed would be the devastating medical and environments effects of nuclear power use gone wrong. Chivian believes in the importance of physicians and other public health professionals getting involved in global environmental issues—that their role is to provide help in translating complex and abstract concepts that are often difficult for the public to understand into human health terms. To this end, he also created the Center for Health and the Global Environment at Harvard Medical—to this day the only organization of its kind at a medical school. Using three important species examples from his most recent book, Sustaining Life: How Human Health Depends on Biodiversity, Chivian describes the overwhelming and sometimes irreversible losses that can occur when we "take for granted what nature supplies us." What can we learn from polar bear physiology that allows them to hibernate for months at a time without developing kidney disease, osteoporosis, or diabetes? Why does the extinction of two gastric-brooding frogs species forever prevent us from developing a potential treatment for peptic ulcers? How can tiny c...