Chapter 56: Conservation Biology and Global Change Biodiversity Conservation biology is a goal-oriented science that seeks to counter the biodiversity crisis, the current rapid decrease in Earth?s variety of life. Extinction is a natural phenomenon that has been occurring since life evolved on earth. The current rate of extinction is what underlies the biodiversity crisis. A high rate of species extinction is being caused by humans. The three levels of biodiversity: genetic diversity species diversity ecosystem diversity The four major threats to biodiversity: Habitat loss Human alteration of habitat is the single greatest threat to biodiversity Introduced species: invasive/nonnative/exotic species Overexploitation: harvest wild plants/animals