Earth's biodiversity -- the profusion of plants and animals that work together to support life -- continues to shrink. Species are going extinct at a rate most scientists find alarming -- possibly as many as 150 a day -- while the populations of many surviving species are declining rapidly. Endangered species range from plants and large animals such as tigers and rhinoceroses to smaller creatures such as insects and honeybees. All play key roles in sustaining healthy ecosystems, which provide a variety of costly environmental services for free, such as filtering water and scrubbing carbon from the air. Some researchers believe the Earth could be approaching a so-called tipping point, in which biodiversity loss causes global ecosystems to change rapidly and dramatically, but other scientists doubt the theory. Meanwhile, there is widespread concern about humanity's ability to sustain itself in a world of diminishing biodiversity if the global population reaches 9.5 billion by 2050, as is projected. While many more areas are being protected today than in the past -- including the bio-rich Amazon rainforest -- conservation efforts are not keeping up with the loss of biodiversity.

Reed Karaim, a freelance writer living in Tuscon, Arizona, has written for The Washington Post, U.S. News and World Report, Smithsonian, American Scholar, USA Weekend and other publications. He is the author of the novel, If Men Were Angels, which was selected for the Barnes and Noble Discover Great New Writers series. He is also the winner of the Robin Goldstein Award for Outstanding Regional Reporting and other journalism awards. Karaim is a graduate of North Dakota State University in Fargo, North Dakota.