Ten years ago, Harvard naturalist Edward O. Wilson estimated that 30,000 species were going extinct every year. Now, scientists are taking an even darker view. According to the World Conservation Union's latest Red List, a staggering one in eight birds, one in four mammals and one in three amphibians are threatened with annihilation. And by the end of the century (because of climate change) species could disappear at 10,000 times the natural rate.
But thousands of new species are also being identified each year. A case in point: the clouded leopard of Borneo and Sumatra. This spring, biologists examined the DNA of the 40-pound, three-foot predator for the first time in 100 years. Previously thought to be members of the same species as clouded leopards from mainland Asia, they found that the Borneo feline has at least 40 unique genetic traits - which makes the two cats as different as lions are from tigers.
Borneo, in fact, is a hotbed of biological discovery. Like the Amazon and the African Congo, the "Heart of Borneo" - a plot of rain forest the size of Kansas - is unusually diverse. On 9.7 hectares, for example, there are about 700 different species of trees, as many as exist in all of North America. And in 2006 alone, scientists identified 30 new species of fish, 16 species of ginger, two tree frogs and three new trees in Borneo's rain forest.
Meanwhile, collections manager William Stanley and his colleagues at the Field Museum in Chicago not only discovered a new species - they identified an entirely new genus. Originally, scientists classified the kipunji monkey as a kind of mangabey. Then a Tanzanian farmer found one of the monkeys (formerly seen only in photos) dead in a trap. Closer analysis revealed that it was the first new African monkey genus described in 80 years. "It was mind-blowing," says Mr. Stanley of his team's 2005 findings.
And yet discoveries like these merely scratch the surface of life on the planet. In all, researchers have named about 1.8 million species - which leaves five million to 30 million species unclassified. Or, depending on where in that broad range scientists stake their claims, 90 per cent of species to go.
Of course, part of the problem is simply finding species that live deep in the ocean, on inaccessible land or in erratic (read: elusive) habits. But there is also another big hurdle to cataloguing even the species already known to exist - the tricky nature of taxonomy.
The question of exactly what makes a species a species is a hotly debated topic among evolutionary biologists. The widely accepted definition is that if two creatures can breed and produce fertile offspring, then they are members of the same species. For instance, horses and donkeys can breed, but their offspring - mules - are sterile. Hence, donkeys and horses are different species.
But this rule of thumb doesn't always ring true. Lions and tigers, for example, can occasionally produce fertile young. And plants and life forms such as bacteria interbreed all the time. "We'll never have one universal criterion by which all specimens may be unambiguously placed in a single species," says Daniel Brooks, a parasite taxonomist at the University of Toronto.
Nonetheless, Prof. Brooks has personally identified hundreds of new species (he admits he lost count a long time ago). "If I've got four or five traits that are different, then I feel better about saying this is a new species," he says.
But it's a slow process. It can take years of scrutinizing the creature's anatomy and comparing it with everything else known to science in order to figure out if something truly distinct has been found. Until then, specimens have been known to sit in drawers for more than 50 years before being identified as a new species.
