Pielou's evenness[3] is an index that measures diversity along with species richness. While species richness is the number of different species in a given area, evenness is the count of individuals of each species in an area. A calculated value of Pielou's evenness ranges from 0 (no evenness) to 1 (complete evenness). When taken into account along with other indices such as Simpson's index or Shannon's index, a more thorough description of a community's structure can be interpreted.[4]
Pielou's approach added mathematical modelling to ecology.[5] Quantifiable analyses could be done with theoretical ecology in areas like population and community ecology. Mathematics would provide insight into, for example, which factors are most significant to ecosystem stability and by how much compared to others.[1]
One of Pielou's papers mentioned the importance and uses of mathematical modelling in ecology as well as their limitations.[6] Population dynamics was better explained as to why they behaved in the ways that they did through modelling. Predictions to an ecosystem's behaviour and its outcomes became more of an explanation as to why, rather than simply a forecast, through the use of such models. If a model was unrealistic, it did not mean that it was wrong. Mathematical modelling allowed the creation of new hypotheses looking into why the model did not match observations. An outcome was not always one or the other, as it might have been different due to unforeseen circumstances or conditions initially thought as unimportant. This allowed mathematical models in ecology to be used as a standard for comparisons with other systems. No two ecosystems are identical, and the significant differences between them could be more easily identified.
^Pielou, EC (1981). "The Usefulness of Ecological Models: A Stock-Taking". The Quarterly Review of Biology. 56: 17–31. doi:10.1086/412081. S2CID84887700.