Measuring Biodiversity

Biodiversity is the total amount of different species that are found in a given ecosystem, biome or the entire planet. It is an indicator of the health of an area. The greater biodiversity there is, the healthier the ecosystem is.

There are several ways to measure the biodiversity of a given area. The two most popular indices are the Shannon Index and the Simpson Index.

However, before we can talk about measuring biodiversity, two key terms we should know are richness and evenness.

Richness: Number of species per sample.

Evenness: Relative abundance of the different species making up the richness of the area.

The Shannon Index

H= Shannon Diversity Index

S= Total # of species in a community (richness)

Pi= Proportion of S made up of ith species

Eh= Equitability (evenness)

Equitability is measured H/Hmax. Hmax=lnS

To learn more about the Shannon Index go here: http://www.tiem.utk.edu/~mbeals/shannonDI.html

The Simpson's Index

It measures the probability that two individuals randomly selected belong to the same species (or other category)

n= total # of organisms of a particular species (in plants, the % of coverage is measured)

N= total # of organisms of all species

There is also Simpson's Index of Diversity, which measures the probability that 2 randomly selected individuals in a zone belong to different subspecies.

The formula is 1-D.

Finally there is the Simpson's Reciprocal Index, which measures the number of equally common subspecies that will produce the observed Simpson's index.

The formula is 1/D

For more information: http://www.countrysideinfo.co.uk/simpsons.htm