APPENDIX 3

INDICATORS OF BIODIVERSITY AT DIFFERENT LEVELS OF SPATIAL AND HIERARCHCAL ORGANIZATION


The simplest indicator of biological diversity is the number of species in a community (richness); yet, this measurement of biodiversity is of limited utility and misses much that is relevant (Walker 1992, Levin 1997). Indices such as Simpson's, Shannon-Wiener's, and Margalef's (Pielou 1977) involve not only the number of species, but also their relative abundance, and provide information about the distribution of importance of the species in a community. The scale of investigation is also important: point, alpha, beta, and gamma diversities address the problem of measuring biological diversity at different spatial scales, namely from a few square meters to hundreds of square kilometers. Moreover, as Wilson (1992) pointed out, "although the species is generally considered to be the 'fundamental unit' for scientific analysis of biodiversity, it is important to recognize that biological diversity is about the variety of living organisms at all levels." For example, the genetic diversity within a population is an important indicator of the range of phenotypic responses to various environmental conditions. Functional diversity is based on functional classification rather than taxonomic classification; it is a measure of how organisms are distributed across functional groups. Finally, community diversity is computed by using the number, sizes, and spatial distribution of communities (sometimes referred to as patchiness).