The application of island-biogeographic theory to patches of habitat: How much land is enough?

The problem of estimating the minimum-sized parcel of land needed to preserve a given suite of species is little-addressed. Two techniques available for such estimations are: (1) ‘the method of island biogeography’, which uses extrapolations of the species-area equation; and (2) ‘the method of addition’, which uses only the actual suite of ‘island’ under investigation. No rationale exists for choosing technique 1 a priori, although the choice is often made. The two techniques produce minimum area estimates which define a spectrum of potential minimum areas. Determination of the real minimum area requirement must rely upon detailed natural-historical observation.