How do we calculate biodiversity?

Posted by Cain Blythe & Alan Feest on 25/09/2012

Biodiversity is de?ned in the 1992 Convention on Biological Diversity (CBD 1992) as:

"the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems."

How do we calculate biodiversity?

Copyright of Thomas Brown

Like many other politically determined conventions the above paragraph contains a large number of compromises and assumptions. The de?nition seems to be determined by the apparent need to list species as a means of recording biodiversity and yet the most commonly used ‘‘biodiversity indices’’ are measures of evenness (Shannon–Wiener and Simpson’s) or dominance (Berger–Parker) rather than lists. However, the list approach does not tell us anything about the balance of individuals of each species, and the ‘‘indices’’ approach can produce the nonsense that a site with 10 species can have a higher ‘‘biodiversity index’’ than a site of 100 species. This is the basis of the comment by Gaston and Spicer (2004) ‘‘. it is clear that no single measure of biodiversity will be adequate. Indeed, given its great complexity, it would be foolish to believe that the variety of life in an area, however small or large that area might be, could be captured in a single number.’’

In light of this it is argued (Feest, 2006 - there is a need to produce a methodology that uni?es sampling philosophy and yet is ?exible enough to cater for the individual characteristics of the taxonomic grouping, which is the subject of biodiversity status assessment.

Biodiversity in this paper can be regarded as a quality of a site that can be extrapolated from a number of measured characteristics of the populations studied that are shown to be present at the time of sampling. The use of this approach can address the whole of, or elements of, the headline indicators of the Convention of Biological Diversity. These indices can be measured through the use of a bespoke and openly available software programme called FUNGIB, created by Dr Alan Feest (available at  The software comprises a set of biodiversity quality indices for professional ecologists and scientific researchers from a single sampling dataset and has the facility to express biodiversity as numerical indices, allowing statistical tests for differences to be used to show significant change in populations and between groups.

The programme allows species lists (such as those used in previous biodiversity assessments) to be compiled in the normal way. However, it can also manage more complex datasets, extracting the value (positive or negative) of individual or groups of indices for predicting the presence or the absence of certain characteristics (such as habitat health and vitality, or the impacts of climate change or pollution). By analysing trends in the survey data it is possible to predict future impacts and to provide guidance in relation to management practices required to maintain favourable conservation status of habitats and ecosystems. The use of numerical indices allows the statistical testing of data for inferring the significance of difference or not.

FUNGIB presents the sample data in the form of a species accumulation chart, plus the following biodiversity quality indices:

Species Richness 

Shannon Wiener Biodiversity Index (for population numbers and relative biomass)

Simpson’s Biodiversity Index (for population numbers and relative biomass)

Berger-Parker Biodiversity Index (for population numbers and relative biomass)

Population Density 

Species Conservation Value Index (mean value and standard deviation)

Biomass Index

Modelled Species Richness (Chao 1 and 2) (estimated value plus standard deviation).

The data provided by this programme is concordant with that needed by the international biodiversity recording programmes such as GBIF, ALTER and EUMON (and later the SEBI 2020 target). It enables consistency of data collection and therefore transboundary comparisons of the potential impacts of policy decisions with respect to biodiversity. There is the facility in the programme to create other indices, such as a nitrogen sensitivity index, if required.