Threatened and endangered species geography

Species have been added unpredictably to the ranks of threatened and endangered owing to variation in petitions, listing procedures, and political will.  Although these erratic decisions chronicle our nation’s effort to conserve biodiversity, such apparent arbitrariness begs the question: Do the places where threatened and endangered species persist co-occur?  Although we do see concentrations of listed species (southern Appalachians, peninsular Florida, arid Southwest, Mediterranean California, coastal areas), conservation science has struggled with how to use this information to move beyond species-by-species conservation strategies that have dominated the 40-year effort to slow the erosion of our biological heritage under ESA.