The biological world of which humans are a part has an immense diversity. There are believed to be from 10 to 100 million species, of which only 1.4 million have been described.

But species are being lost all the time as their habitats are built on or converted to agriculture.

There are believed to be many species which produce chemicals of use to humans in, for example, medicine. But if these are unknown to western scientists (though often known to the native inhabitants) their loss will prevent their use.

However, at least as important is the fact that our food crops are limited in number and depend on a small gene pool. (Hunter gatherers used a larger number). Plant diseases can weaken existing crops. If the wild species have disappeared it may not be possible to breed new disease resistant crops from the wild genes.

Traditional varieties of such crops as wheat and maize are lost when farmers are encouraged to use modern hybrid varieties instead of their traditional varieties. But the hybrid types have often been bred from the traditional varieties.

In Europe the Commission has tried to prevent the sale of unapproved varieties of vegetables and fruit. It can be argued that each traditional variety was adapted to the area where it was found so that new varieties imposed over a whole area are likely to be less suited to particular climatic conditions in any one locality. Therefore the limitation is unacceptable (it is believed to have been adopted as a result of commercial pressure from seed producers).

On a larger scale the different functions of species are often unknown. The elimination of species may prevent their ecological function being done. The results of this are impossible to foresee but can be assumed to be bad. As the rule in a complex system is that any change to one component will affect all the others, the mass extinctions may perturb the world system in unforeseeable ways.

Forests are an important source of diversity. The nearer the equator, the larger the number of species found. The tropical forests are endangered by a demand for timber from the industrial countries: US, Europe and Japan and increasingly from China. Many of the species may be being lost, even though the native inhabitants are aware of benefits from many of them. This is damage apart from the general climate regulating qualities of the forest as a whole. In the near future, if not already, the main cause of species loss will be climate change.

Important BBC tv series on interdependency
BBC series on interdependency of all species.

The only way to prevent species extinction is to preserve their habitats. But the main cause of habitat destruction (or modification) is human population pressure. If the human population goes on rising, land will continue to be taken for agriculture and the wild species be displaced. Climate change up to two degrees is probably already impossible to avoid, so many species will be squeezed out of their habitats.

What may be needed is a love of diversity rather than the urge to make everywhere the same, and to grow the same crops everywhere.

The UN Conference on Environment and Development proposed a treaty on diversity by which drug companies would pay a part of their royalties for substances discovered in rain forests and other natural systems. The treaty was opposed by the United States, presumably to protect US industry. (Signed by President Clinton) The object of the treaty was to encourage those states with wilderness to preserve it rather than cut it down for grazing or building and agriculture.