Biodiversity, long championed by environmentalists, is finally enjoying its moment in the sun. Suddenly everybody but President Bush wants to defend the Earth's stock of species, down to the last ant or spider. But nobody knows how many species there are.
A British expedition in central Guyana, co-ordinated by Dr Mike Gillman and Dr Mark Johnston, of the Open University, may produce some of the answers. Between now and the end of November, 22 scientists in a variety of disciplines will look at bats, other mammals, birds, insects and plants in a phased programme to measure biodiversity in the Iwokrama rain forest, an almost undisturbed 360,000-hectare area where a sustainable forestry programme has been started with help from the Commonwealth Secretariat.
Dr Gillman explains that at present nobody can say what sustainable means when applied to the species living in the forest.
He asks: "Is it possible to fell 10 per cent of the trees without reducing the variety of species? Which trees are the most critical? We do not know. In the long term we would like to carry out experiments to discover the answers, but the immediate objective is simply to establish what there is there."
The scientists will first identify five or six distinct areas in the forest with different vegetation and morphology. Within every area they will identify zones of one hectare that are typical of the area as a whole. Within every hectare counts will be made of mammals and insects. The scientists will study the variety of trees and observe which are fruiting. To identify and count mammals and marsupials, 250 traps will be set in every square hectare, and the creatures caught will be counted and marked. They will then be freed, and from the proportion caught a second time, an estimate of the total population can be made.
Densities of animals are expected to be low, but the same cannot be said of insects. A naturalist who visited the area in the 1930s said there were 1,000 species of butterfly alone, against 59 in the whole of the UK. Insects will be counted and identified by a more brutal method. A fog of insecticide will be released through the forest canopy and the rain of insects pouring down will be caught. Dr Nigel Stalk, at the Natural History Museum in London, will be responsible for identifying the huge number of specimens sent back.
A similar experiment in the Brunei rain forest, covering only ten trees, found 20,000 insects belonging to 2,500 different species. So far, in the entire world, a total of a million insect species have been described, but a further five to seven million species are thought to remain undiscovered, about 40 per cent of them beetles.
So the Guyana expedition seems certain to discover many new species, examples of which will be deposited in institutes in Guyana to build up national collections.
Ultimately, Dr Gillman would like to continue the work by investigating how sensitive all these species are to disruption. Then, for the first time, sensible estimates of the likely loss of biodiversity from tree-felling or other forest disturbance may be possible. Dr Gillman says that will take at least five years and require substantial funding.
