Estimates of the number of species vary widely because many species-rich ecosystems, such as tropical forests, contain unexplored and unstudied habitats. Among small organisms in particular many are unknown. For example, it is thought that less than 1% of the world's bacterial species have been identified.

The most significant threat to biodiversity comes from the destruction of rainforests and other habitats. It is estimated that 7% of the Earth's surface hosts 50-75% of the world's biological diversity. Costa Rica, for example, has an area less than 10% of the size of France but possesses three times as many vertebrate species.

Loss of biodiversity

Since the start of the 20th century there has been the most severe and rapid loss of biodiversity in the history of the planet. We are in a period of mass extinction. In the geological past, several periods of extinction have occurred and they appear to be associated with catastrophic events, such as a large meteorite hitting the Earth or massive volcanic activity. It is believed that the current loss of species is mainly due to the loss of habitats. Although the most significant threat to biodiversity comes from the destruction of rainforests, even in Britain the loss of species continues at a worrying rate. On average each county in Britain loses a species every ten years.

The Rio Summit

In 1992 an international convention for the preservation of biodiversity was signed by over 100 world leaders (the Rio Summit). The convention called on industrialized countries to give financial and technological help to developing countries in order to allow them to protect and manage their natural resources, and to profit from the commercial demand for genes and chemicals from wild species. However, the convention was weakened when the USA refused to sign because of fears it would undermine the patents and licences of biotechnology companies.

Marine protection areas

In 1995, 1,306 sites worldwide were designated as marine protection areas (MPAs). Of these, 155 areas were singled out for further protection, including the Bering Strait and Kachemak Bay, both in Alaska. The MPAs were selected on the basis of genetic diversity, biological productivity, and the extent to which they provided habitats for endangered species.

essays

Earth Summit

Extinction: A Race against Time

The Fate of the Rainforests

Forest Fires in Borneo

Human activity and the enviroment

Habitats and diversity

weblinks

Animal Diversity Web

ARKive

Biodiversity: Measuring the Variety of Nature

‘Biodiversity Loss Threatens New Treatments’

Center for Biodiversity: Study of Plants and Animals

Exploring the Environment