Biological diversity (or biodiversity) refers to the variety of ecosystems and species of plants and animals that can be found in nature. There are three levels at which biodiversity is important: genes, species and ecosystems. McNeely and his colleagues describe these levels:

Genetic diversity is the sum total of genetic information, contained in the genes of individual plants, animals and microorganisms that inhabit the earth. Species diversity refers to the variety of living organisms on earth and has been variously estimated to be between 5 and 50 million or more, though only about 1.4 million have actually been described. Ecosystem diversity relates to the variety of habitats, biotic communities, and ecological processes in the biosphere, as well as the tremendous diversity within ecosystems in terms of habitat differences and variety of ecological processes. (1990, p. 17)

When people talk about preserving biodiversity they generally mean that a full and diverse range of plant and animal species should be maintained. It has been argued that current human activities are causing the mass extinction of species at a rate never before experienced. Several species become extinct each day, while scientists estimate that the extinction rate in pre-human times was just a few species per thousand years. In the past, species were often protected because technologies were relatively harmless, and population patterns and cultural customs and taboos prevented overexploitation.

The rate of extinction of native mammal species in Australia today is particularly high compared with other countries. As in other countries, extinction has been caused by the removal of forests and bushland for agriculture, forestry and urban development; competition from introduced and cultivated plants and animals; and pollution of and changes to waterways.

Environmentalists argue that the destruction and modification of habitats that results from economic activity is threatening the ability of life forms to evolve and therefore to survive through adaptation. They differentiate between conservation, which means maintaining the ability of species to evolve, and preservation, which provides only for the maintenance of individuals or groups of species, but not for their evolutionary change. This latter view was expressed by Stuart Harris, chair of some of the ecologically sustainable development working groups, when he said that 'we should set aside representative samples of the range of Australia's biodiversity' (1991, p. 8) and the Business Council of Australia, who concluded that the only feasible policy is no extinction of important species.

Some economists argue that an underlying cause of species loss has been that the value of biodiversity has not been included in measures of national wealth. They say that many of the benefits arising from biodiversity have not been exchanged in the market place and as a consequence have been ignored or grossly underestimated. This means that the costs of protecting areas and preventing developments that are incompatible with species protection have seemed too high compared with the benefits.

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Source: Sharon Beder, The Nature of Sustainable Development, 2nd edition, Scribe, Newham, Vic.,1996.

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