Hard choices

... about which regions to conserve have just become easier, thanks to an experiment in Uganda

Published: Thursday 15 October 1998

THE biggest challenge before us as we face the new millennium is not developing better, faster and cheaper technologies, but trying to save whatever now remains of the planet's biodiversity. There are various ways to do this, but before these methods can be adopted, scientists and environmentalists have to identify which regions are to be protected. And this process of identification can turn out to be an expensive exercise, agree most experts. However, a new study of forests in Uganda shows how cheaper surveys of birds and butterflies can accurately indicate the best areas to protect.

Right now, conservation is really a game of numbers. Conservationists attempt to set aside combinations of areas that preserve the greatest number of species. But counting all the species in a given area can often be difficult, and occasionally even impossible. In cases where it can be done, it invariably turns out to be expensive and time-consuming. For example, a recent survey of 2,452 species of birds, butterflies, large moths, woody plants and small mammals in over 50 forests in Uganda cost researchers five years and an astronomical sum of over a million us dollars.

Andrew Balmford of the University of Sheffield, UK, teamed up with the researchers who carried out this back breaking work to look for a cheaper method of surveying biodiversity. They wanted to see if they could get enough information from fewer groups of species to enable them to select a combination of land parcels that would contain the greatest biodiversity. "We asked: can we focus on just one or two groups, rather than on all five?" Balmford says.

But they soon discovered that areas with many species of butterfly, for instance, did not necessarily have an equal number of bird or moth species. Further, in many cases, two different forests may be inhabited by the same species, so setting both aside would not necessarily increase the number of species conserved. "It's important that a site is not only rich, but that it has different species to other sites you pick," he says.

So the researchers developed a computer software to calculate the combination of forests that would contain the greatest number of different species while adding up to a fixed total area of land. The software counted species that appeared in more than one forest only once. When asked to consider only birds or only butterflies, the software accurately selected the groups of forests with the greatest overall diversity.

John Lawton, the director of the Centre for Population Biology at Imperial College's Silwood Park campus in Berkshire, UK, says the Ugandan experiment could prove crucial for future conservation efforts. "We have a practical tool now" he says. "If I had to make hard choices in the absence of perfect information - and we never have perfect information - one would use this method."

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