Conservation biologists are applying their understanding of population, community, ecosystem, and landscape dynamics in establishing parks, wilderness areas, and other legally protected nature reserves. Choosing locations for protection often focuses on biodiversity hot spots. These relatively small areas have a large number of endangered and threatened species and an exceptional concentration of endemic species, those that are found nowhere else. Together, the “hottest” of Earth’s biodiversity hot spots total less than 1.5% of Earth’s land but are home to a third of all species of plants and vertebrates. There are also hot spots in aquatic ecosystems, such as certain river systems and coral reefs. Because endemic species are limited to specific areas, they are highly sensitive to deprivation of their natural environment. At the current rate of human development, some biologists estimate that loss of habitat will cause the extinction of about half of the species in terrestrial biodiversity hot spots in the next 10 to 15 years. Thus, biodiversity hot spots can also be hot spots of extinction. They rank high on the list of areas demanding strong global conservation efforts. Concentrations of species provide an opportunity to protect many species in very limited areas. However, species endangerment is truly a global problem, and focusing on hot spots should not detract from efforts to conserve habitats and species diversity in other areas.