Species are going extinct at rates 100 to 1,000 times faster than they did before humans walked the Earth. With increasing concern, scientists are now realizing that loss of species can directly affect our health—perhaps most significantly through diminishing our chances of discovering better medicines and diagnostic tests. This gallery, adapted from the book Sustaining Life: How Human Health Depends on Biodiversity, features six species currently faced with extinction and their potential benefits to medicine.

At left, 'The Blue Marble' from NASA Goddard Space Flight Center.