Biodiversity

Definitions and Approaches

Biodiversity is often described in hierarchical terms including genetic diversity, species diversity, and ecosystem diversity. Genetic diversity refers to the genetic differences between populations of a single species and between individuals within a single population; species diversity refers to the frequency and variety of species within a geographical area; and ecosystem diversity refers to the variety of habitats, the dynamic complexes of plant, animal, and microorganism communities and their nonliving environment, which interact as a functional unit and their change over time.

Varieties of rice, number of plants and animal species coexisting in a geographical area, and number of ecosystems in a forest area exemplify genetic, species, and ecosystem diversity, respectively.

Species diversity can be further distinguished into three types: alpha, beta, and gamma diversities. Alpha diversity refers the diversity at one site, i.e., the number of species coexisting within a single biological community. Beta diversity is species turnover across an environmental or geographical gradient, and gamma diversity refers to the total number of species in all habitats within a region. The “region” means a geographical area that includes no significant barriers to dispersal of organisms.

Some scientists have argued for the necessity of making distinctions between “functional” and [Page 119]“compositional” perspectives in approaching biodiversity, rather than using hierarchical terms. The functional approach is primarily concerned with ecosystem and evolutionary processes, while the compositional approach sees organisms as aggregated into populations, species, higher taxa, communities, and other categories.

Despite a wide range of definitions, biodiversity emerges as a concept linked primarily to the idea of biological variation that is largely unknown in its extent, and its future values.

Why Does Biodiversity Matter?

Biodiversity is important for human beings in a number of ways. First, species have utilitarian (subsistence and commercial) value to humans. Diversity of biological organisms is a crucial component in the livelihood of many poor people, as they often depend on the diversified plants and animals to meet their nutritional, medicinal, and energy needs. Different cultures and societies use, value, and protect these resources and services in a variety of ways. Moreover, there are huge prospects of benefiting from unknown genetic and species diversity. Second, biodiversity represents the natural balance within an ecosystem. Detoxification and decomposition of wastes by biological communities (particularly bacteria and fungi); generation and renewal of soil fertility, including nutrient cycling; and pollination of plants are just a few examples of ecological services associated with biological diversity. As biodiversity is reduced, internal and natural controls must be replaced by more artificial controls (in the form of management and resources), which may not be successful to the same extent. Third, species have intrinsic value. Many argue that protecting them from the terrible finality of extinction by saving their habitats is an ethical responsibility.

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