For example, many agricultural farmers cultivate monocultures- large populations of genetically identical plants- therefore having the same abilities and inabilities. Although all the plants may flourish in the same conditions at the same time, this also makes them all susceptible to the same parasite or changing environmental conditions all at the same time. Closely related to Genetic Diversity is Species Diversity, which is said to be the typical focus of scientists as it easier to work with. This is because species are easily identifiable with out the use of a microscope as opposed to genetic diversity or ecosystem diversity, which requires complex procedures to be taken over a prolonged period of time. .
This level of diversity refers to both the species richness, the number of species there are currently interacting together and their relative abundance, the ratio of common species to rare ones, with in a community. A community is classified as "an assemblage of species living close enough together for potential interaction"" (Campbell, Reece, Mitchell-1999- Biology 5th edition, pg 1107). Species diversity is of particular importance because each species of plants, animals or microorganisms plays a very distinct role in the functioning of the ecosystem. So the addition of a completely new variety of plant or animal or the rapid decline in the population, which often leads to extinction, of another species affects the entire balance of the ecosystem. For example a deciduous forest in West Virginia has 10 tree species all growing successfully there, although the general population of trees is made up 84% yellow poplar and sassafras, while four out of the ten species are only represented by singular trees. Thus, this particular forest would be an example of low species diversity.
Although linked with species diversity, ecosystem diversity is perhaps the level of diversity that is least understood by scientists because of its complexity.