Is Global Warming Leading to Extinction?

At the end of a rugged road, two hours from downtown San Diego, scientists are hoping to find a Checkerspot butterfly -- and avoid stepping on a few tiny black caterpillars.

"In the 1950s, over the whole city, you literally had millions of these [Checkerspots] flying around -- so thick, you had to turn on the windshield wipers," says biologist Camille Parmesan with the University of Texas in Austin.

Meanwhile, other scientists are finding similar voids among Harlequin frogs usually found in the Monteverde Cloud Forest Preserve of Costa Rica.

"They used to be so common, you had to be careful not to step on them as you walked along the stream margins," says Alan Pounds, an ecologist and resident scientist at the preserve. "There's an overall effect that is related to the climate change. But the most dramatic changes, the frightening changes are the complete extinctions of certain species."

The wild orchids here are also in danger from global warming, say scientists.

"If the climate of Monteverde continues to change, I don't see how extinction can be avoided," says Karen Masters, a conservation biologist for the Council for International Educational Exchange at Monteverde.

But the changes -- and missing plants and animals -- aren't just in the lush forests of Costa Rica. On the other side of the planet on a remote jungle ridge in Madagascar, an American expedition finds three entire species of frog missing.

"Perhaps they have gone extinct," says Christopher Raxworthy, associate curator of the American Museum of Natural History's Division of Vertebrate Zoology. "If you had an increase in temperature, this is exactly what you would expect."

Global Warming, Global Threat

All over the planet, hundreds of scientists are finding plants and animals suddenly scattering, withering or outright disappearing as our world approaches sustained temperatures higher than today's species ever evolved to be able to survive in.

The new heat wave is attacking in many ways -- from melting the sea-ice that polar bears need for hunting to bringing tropical rains two months too early, so plants blossom too soon to feed the animals that depend on them.

Three separate scientific survey studies, which pull together hundreds of field studies from around the world, add to the same picture. The increase in the average global temperature is causing havoc in many ecosystems -- and on a scale that's hard, at first, even to imagine.

One study by 19 established scientists on five continents, predicts "on the basis of mid-range climate warming scenarios, for 2050, that 15 [percent] to 37 percent of species in our sample will be committed to extinction."

"Do we want to destroy the creation? That's the question," says Edward O. Wilson, professor and curator of entomology at the Museum of Comparative Zoology at Harvard University. "That's what we're doing -- and at an accelerating rate."

For half a century, Wilson has uncovered the cohesive complexity of all life on Earth and focused on how its rich biodiversity is being destroyed by human attacks, ranging from spreading pesticides to wiping out wildlife habitats. He's found it painful to assess how global warming is now piling its assaults on top of all the others.

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