What do long-dead animals, satellite technology, and biologists counting lizards have in common? Together they may be able to help predict population distributions of animals threatened with extinction.

This is particularly important as the rate of habitat loss accelerates in regions where very little data is available.

"Before you can really conserve a species one of the fundamental pieces of information you need to know is where they occur," said Christopher Raxworthy, associate curator of vertebrate zoology at the American Museum of Natural History. "It's amazing just how poor our understanding of species distribution in some areas is. This is particularly true in the tropics which are both poorly studied and contain the greatest number of species."

A Global Biodiversity Assessment issued in 1995 estimates there are approximately 1.75 million species—animals, plants, fungi, and micro-organisms—known to science. An estimated 12 to 13 million remain as yet unidentified. Tropical rain forests are estimated to contain more than half the species on the planet. Yet loss of habitat, climate change, human encroachment, and reduction of species' gene pools all threaten to greatly reduce the planet's biodiversity.

"With the loss of tropical forest at the rates we're currently seeing, we're really the last generation of biologists who will have the opportunity to identify and set up new reserves," said Raxworthy. "Time is running out."

Chameleons in Madagascar

Raxworthy and colleagues developed a computer model to study chameleons, lizards known for their ability to change color depending on their mood or surroundings, in Madagascar.

Madagascar, which lies off the coast of Africa, is the fourth largest island in the world. Tens of millions of years of isolation from the African mainland resulted in making the island nation a hotbed of species found nowhere else in the world. According to Conservation International, at least 90 percent of the reptiles found on Madagascar exist only there.

By combining on-the-ground field evidence, satellite data, and information collected from museum specimens—some dating back to the 1800s—the scientists generated layers of maps that not only correctly predicted where known populations were living, but also identified areas that contained chameleon species previously unknown to science.

Speeding up the process of identifying species distributions could help prevent the loss of threatened animals in a range of settings.

"A government or organization could want to protect a particular species, or set aside a reserve with the maximum amount of unprotected biodiversity, or set aside land to protect the highest number of species," he said. "Just knowing where species are with a reasonable amount of accuracy can be useful."

Beyond Madagascar

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SOURCES AND RELATED WEB SITES American Museum of Natural History Chameleon Conservation Conservation International's Biodiversity Hotspots Wildlife Conservation Society