Karnataka 26. Uttaranchal

SAQ 3

By citing an ecosystem, (say tropical forest, or grassland) explain how different levels of diversity are interrelated.

5.4 MEASURING BIODIVERSITY

Conservation and management of biodiversity require measurement of biodiversity because it is important to make choices about “what, where, and how” to conserve. Measurement can be considered at all three levels of biodiversity: genes, species and ecosystems. As they are all interrelated, however, it is difficult to talk about measures at one level while ignoring the others. It is also difficult to measure biological diversity because there are so many ways of measuring it, and the situation is made more complex because of problems associated with the interpretation of data resulting from the different forms of measurement.

5.4.1 Measuring Species Diversity

The measurement of species diversity provides an important preliminary assessment of overall biodiversity. There are many ways by which species diversity is measured i.e. species richness, taxonomic diversity, taxonomic uniqueness and species-diversity indices.

• Species richness

This is the most widely used measure of species diversity. In simple terms it is a count of the total number of species in a given area. It gives equal weightage to all species and does not take into account the number of individuals that represent a particular species. A large number of individuals of a single species will result in greater genetic diversity, and thus positively influence overall biodiversity.

Complete counts of species richness of an area are rarely possible, so that the measure of species richness is often based on sampling smaller representative sites within the area to be assessed. Accuracy of sampling is thus important in estimating species richness of a given area. To describe the complex spatial patterns of biodiversity, ecologists and biogeographers have found it useful to express species richness into four major categories:

1. Point richness

2. Alpha (α) richness, 3. Beta (β) richness, and 4. Gamma (γ) richness

Point richness refers to the number of species that can be found at a single point in space.

Alpha (α) richness refers to the number of species found in small, homogenous area. Alpha diversity refers to the diversity in a particular area or ecosystem and is usually expressed by the number of species (i.e. species richness) in that ecosystem.