U.S. Environmental Protection Agency


Date of this Version



Published in Social-Ecological Resilience and Law, ed. Ahjond S. Garmestani and Craig R. Allen (New York: Columbia University Press, 2014).


U.S. government work.


Biological diversity can be considered both temporally (Le., evolutionary time) and/or spatially and reflects the number, variety, and variability of organisms. It includes diversity within species (Le., genetic and morphological), between species (Le., alpha and beta), and among ecosystems (Le., beta and gamma). Over the past few hundred years, human activities have increased species extinction rates by as much as 1,000 times above the background rates that were typical over Earth's history (Figure 2.1) (Millennium Ecosystem Assessment 2005; but see He and Hubbell 2011). In the United States, there are approximately 1,900 species listed as threatened or endangered, with potentially thousands more at risk (U.S. Fish and Wildlife Service [USFWSj 2011a). The challenge of addressing biodiversity loss and the inevitable but largely unknown consequences associated with it presents a "wicked problem" characterized by complexity and high uncertainty (Farley 2007).