Explain what the term biodiversity means, and why it is important.

Biodiversity can be defined broadly as the variety of life of Earth. The Convention on Biological Diversity includes variation between species (species diversity), within a species (genetic diversity) and between ecosystems (ecosystem diversity) within their definition.

Biodiversity is important on many levels, from the scale of an ecosystem, to the global scale. An ecosystem is a community of organisms that interact with each other and their environment. A great way of visualizing an ecosystem is through a foodweb, which shows the transfer of energy between organisms within the system, and how each organism depends on one another. Biodiversity at this scale is important because it ensures ecosystem stability. With a large number of species present in an ecosystem the extinction of one is less likely to have a major impact on the rest of the system. This is because those that rely on the extinct species for food, are able to adapt their diets given the variety of species present. In addition, genetic diversity within a species is important because a large gene pool permits adaptation to a wide range of changing environmental conditions, through natural selection. This is particularly important when faced with rapid climate change.

Biodiversity is also incredibly important to humans. Ecosystems provide humans with 'ecosystem services' such as the maintenance of the climate, sources of timber, food, medicine and the removal of pollutants. A greater number of species present, the more ecosystem services the system can provide. For example on a global scale, the Earth's biosphere provides a major global carbon sink, offsetting a large amount of fossil fuel emissions. Biodiversity ensures the maintenance of this system, and buffers a rise in atmospheric carbon dioxide concentrations. Without this sink climate change would take place at a rate significantly greater than we are experiencing today.