Measurement of biodiversity

Biodiversity is usually plotted as the richness of a geographic area, with some reference to a temporal scale. Types of biodiversity include taxonomic or species, ecological, morphological, and genetic diversity. Taxonomic diversity, that is the number of species, genera, family is the most commonly assessed type. A few studies have attempted to quantitatively clarify the relationship between different types of diversity. For example, the biologist Sarda Sahney has found a close link between vertebrate taxonomic and ecological diversity.

Conservation biologists have also designed a variety of objective means to empirically measure biodiversity. Each measure of biodiversity relates to a particular use of the data. For practical conservationists, measurements should include a quantification of values that are commonly shared among locally affected organisms, including humans. For others, a more economically defensible definition should allow the ensuring of continued possibilities for both adaptation and future use by humans, assuring environmental sustainability.

As a consequence, biologists argue that this measure is likely to be associated with the variety of genes. Since it cannot always be said which genes are more likely to prove beneficial, the best choice for conservation is to assure the persistence of as many genes as possible. For ecologists, this latter approach is sometimes considered too restrictive, as it prohibits ecological succession.

Taxonomic diversity

Biodiversity is usually plotted as taxonomic richness of a geographic area, with some reference to a temporal scale. Whittaker described three common metrics used to measure species-level biodiversity, encompassing attention to species richness or species evenness:

• Species richness - the simplest of the indices available.
• Simpson index
• Shannon-Wiener index

More recently, two new indices have been invented. The Mean Species Abundance Index (MSA) calculates the trend in population size of a cross section of the species. It does this in line with the CBD 2010 indicator for species abundance. The Biodiversity Intactness Index (BII) measures biodiversity change using abundance data on plants, fungi and animals worldwide. The BII shows how local terrestrial biodiversity responds to human pressures such as land use change and intensification.