Issue Information

There are many ways to measure species diversity. The simplest is species richness, that is, a simple count of the number of species present in a community. However, it can also be useful to take into account additional information. Species composition adds the dimension of species’ identity. Understanding of species composition is one of the foundations of community ecology. For example, if you are running a nature preserve, the number of species may not be nearly as important as the presence of certain native, rare, and/or endangered species. An additional level of detail is added by examining the relative abundances of species in a community. Abundance refers to the number of individuals within a species. Species diversity combines both species richness and species composition by measuring the relative abundance of each species, i.e. how common or rare each a species is compared to other species in the community. Relative abundance information allows a community ecologist to examine questions of still greater detail regarding the dynamics of ecological communities, such as which species are most dominant, which species are rare, etc. The Shannon-Weiner Diversity Index (H) is one calculation ecologists use to estimate diversity that includes both species richness and relative abundance.