biodiversity and how to measure it

Biodiversity

Biodiversity exists at three interrelated levels: species diversity, genetic diversity, and community-level diversity. When we talk about plant biodiversity, we refer to the full range of plant species, the genetic variation found within those species, and the biological communities formed by those species. For vascular plants, biodiversity includes all species of ferns, gymnosperms, flowering plants, and related smaller groups such as clubmosses and horsetails. The genetic variation found within populations and among populations arises through the mutation of individual genes or chromosomes and is rearranged by genetic recombination during the sexual process. Genetic variation is important not only for the survival and evolution of species; it is also important to people for breeding improved crop plants with higher yields.

Biological diversity also refers to all biological communities, including temperate forests, tropical forests, grasslands, shrub lands, deserts, freshwater wetlands, and marine habitats. Each of these biological communities represents an adaptation of plants to particular regimes of climate, soil, and other aspects of the environment. This adaptation involves ecosystem interactions of each biological community with its physical and chemical environment. For example, the ability of a forest community to absorb rain water and slowly release the water into streams and the ability of a swamp to process and detoxify polluted water are both aspects of ecosystem-level biological diversity that are of central importance to human societies.

Measuring Biodiversity

Biological diversity can be measured in various ways, each of which captures some of the overall meaning of biological diversity. The most common method of measuring biological diversity is simply to count the number of species occurring in one particular place, such as a forest or a grassland. Since it is not possible to count every species of plant, insect, fungus, and microorganism, the usual procedure is to count certain types of organisms, such as birds, butterflies, all flowering plants, or just tree species. This type of local diversity of species is usually referred to as species richness or alpha diversity. A tropical rain forest might contain three hundred or more tree species in a square of forest measuring 400 meters on a side, whereas a temperate forest of equal area might contain only forty tree species. Biological diversity can also be measured in larger areas. For example the country of Colombia has more than fifty thousand species of higher plants, in contrast to sixteen hundred species for the United Kingdom and nearly sixteen thousand for Australia. This type of regional or large-scale diversity is referred to as gamma diversity.