The Usefulness of Evenness

Abstract

Evenness measures similarity in abundance across species. The term ‘evenness’ was introduced to ecology in 1964, but debate persists about precisely how to measure it and its usefulness as a concept. Here I provide a perspective on both matters. For how to choose evenness metrics, I echo previous calls for the application of the Lorenz-consistency axioms. These axioms are largely non-controversial but have often been neglected, leading to some ongoing use of evenness indices with unintuitive properties. Two widely used evenness metrics, Hill evenness and mean pairwise similarity, satisfy the axioms and are recommended. To assess the usefulness of evenness in ecological research, I focus on two case studies. The first explores how evenness can drive community biomass. The second explores how evenness can indicate the strength of immigration into an ecological community. I conclude that, with appropriately chosen metrics, the concept of evenness can facilitate productive research programmes. Therefore, despite some recently raised objections to it, evenness is a useful concept in ecology.