The Rarest of the Rare

In a world of increasingly unpredictable environmental pressures, conservationists are focused on identifying the rarest of rare animal and insect species before they disappear altogether.

While these species vary considerably -- some are birds; others are reptiles, fish and mammals -- they have one thing in common: Each one evolved in a small region and is found nowhere else, making these species especially vulnerable to extinction.

They lie on a continuum of imperilment, according to the International Union for Conservation of Nature (IUCN), a private nongovernmental group that publishes an annual "Red List" classifying species as critically endangered, endangered or vulnerable to extinction.

A different group, the Wildlife Conservation Society recently published "State of the Wild," focusing on a dozen species on IUCN's Red List, a varied collection that includes the Abbott's booby, which nests on Christmas Island in the Indian Ocean, and the Burmese roofed turtle, which used to be abundant in Burma before hunters targeted the creatures and their eggs.

The threats that have helped devastate vulnerable species are similarly varied. Fishing bycatch is a key reason why there are 150 vaquita porpoises left in the northern Gulf of California, the one region of the world where they live. In Sri Lanka, water pollution and the destruction of rain forest habitat have nearly wiped out Tetrathemis yerburii dragonflies.

While total number of species on the Red List continues to rise, some are recovering, according to WCS program assistant Catherine Grippo: Of the 381 species reassessed in 2007, 74 had gained in numbers.