Conservation biology is the study of the biological diversity—biodiversity for short—of Earth. Biodiversity is the variety of different living creatures, both plants and animals. Conservation biology is a relatively new field of study, having its start in the 1980s. It applies the principles of many sciences in order to preserve biodiversity throughout the world.

While at the end of the twentieth century the number of described species was about 1.7 million, estimates put the total number of species at 5 to 30 million. Many scientists believe that Earth is experiencing the greatest episode of mass extinction since the extinction of the dinosaurs 65 million years ago. Current rates of species extinctions throughout the world are believed to be 50 to 100 times greater than rates prior to human impact. In tropical forests, the extinction rates are believed to be 1,000 to 10,000 times higher than the expected rate. Given the current rates...