" Biodiversity is the variety of life
and its processes; and it includes the variety
of living organisms, the genetic differences
among them, and the communities and
ecosystems in which they occur.”
Biodiversity is the amount of the different species, plants and animals, that can be found within an ecosystem, biome or the entire Earth.
The biodiversity index help us to determine the amount of species in a given area. A very simple index goes as the following example:
| = biodiversity index |
The previous example is very basic. It might be used when little information is available and the experience of the analyst is limited. In order to carry out a better measurement of biodiversity is important to don't include only the number of species, but also the abundance of each specie.
In simple terms the main two aspects are the richness and the evenness.
Richness of species affect more directly the amount of biodiversity than the evenness.
The Simpsons Diversity index covers those two. It can actually refer to any one of 3 closely related indices:
where S is the number of species, N is the total percentage cover or total number of organisms and n is the percentage cover of a species or number of organisms of a species. In this form, D ranges from 1 to 0, with 1 representing infinite diversity and 0 representing no diversity.
Another widely used index is the Shannon index of diversity. It turns out to be poorer than other indices on most criteria:
pi = the proportion of individuals of species i in the sample, pi = ni/N.
IShannon = H = - Σ pi ln(pi)
The importance of these indices lies on:
- Understanding community structure.
- Outline odd behaviors
- Identify the rarity and commonness of an specie within a community
References.
"How to Calculate a Biodiversity Index." American Museum of Natural Art, n.d. Web. 17 Aug 2010. .
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