Population Extinction and the Biodiversity Crisis¹

Abstract

During the last decade the public has become increasingly aware of the accelerating loss of species from Earth’s biota. But the loss of species is only one aspect of the extinction crisis, and in many parts of the world may not be the most important facet of the decay of biological diversity. The focus among biologists upon the conservation of species [see, for example, Pimm and Gittleman, 1992; Reid and Miller, 1989; Scott et al., 1987; Wilson, 1989] is somewhat ironic because debates have raged (and persist) over how to define a species along the continuum of differentiation between organisms [Ehrlich, 1961; Ehrlich and Raven, 1969; Masters and Spencer, 1989; Mayr, 1970; Patterson, 1982; Wiley, 1981; Willis, 1981]. This chapter examines the implications of the extinction of populations and attempts to assess its importance relative to the extinction of species.

¹ An earlier and shorter version of this chapter appeared as Ehrlich and Daily [1993].

² We greatly appreciate the helpful comments on an earlier draft of the manuscript provided by Carl Folke, Karl-Göran Mäler, and Charles Perrings (The Beijer Institute) and Anne H. Ehrlich, Dennis Murphy, and Thomas Sisk (Center for Conservation Biology, Stanford). This work was supported in part by a grant from the W. Alton Jones Foundation and by donations from private individuals.