Threatened and Endangered Species Geography

An estimated global extinction rate that appears to be unprecedented in geological time (May 1990) has heightened concern for the increasing number of rare species. Moreover, this elevated extinction rate is being attributed to the activities of humans rather than to some calamitous natural disaster (Pimm et al. 1995). Conservation efforts to slow biodiversity loss have traditionally focused on species with few remaining individuals, based on the assumption that they are the most vulnerable to extinction (Sisk et al. 1994). Consequently, rarity has been used as an important criterion for identifying which species should be the focus of conservation efforts.