Is Global Warming Leading to Extinction?

"I'm optimistic by nature, but I have to admit it's getting scary," says Wilson. "Most people who've analyzed the situation believe that we could -- again, if the situation is unabated -- could lose half the species of plants and animals in the world by the end of the 21st century. We're simply plinking them out of existence -- in many cases without even knowing what they are."

Nobody meant for this to happen. And as hard news about global warming has become visible -- glaciers melting fast around the world, more frequent spikes in heat-driven weather -- there's been emotional debate. Some who deny it's even happening are accused by others of just being in denial.

It's not surprising there's been such disagreement and confusion about global warming because, in one sense, it's quite simply the biggest problem we've ever faced. It's affecting the entire planet -- and all at once.

And since the warming atmosphere envelops all life forms in its blanket, this is also the most complex story ever. Many millions of species with their intricate patterns of inter-dependence are each disrupted differently.

So to begin to understand it, we need people who are not afraid of complexity, who even enjoy it -- such as the scientists we sought out for this report.

Butterfly Lessons

First, biologist Camille Parmesan explains a few basics of the worldwide problem, with the help of the Checkerspot butterfly.

"This is their main food plant, goldfields intermixed with plantain," says Parmesan. "They really like these little white and yellow flowers because they have very short tongues. You can see him probing into the flower."

Parmesan is also the lead author of a global survey that finds half of all plant and animal species on Earth are already affected by the warming.

But her specialty is butterflies. Around the world, she's found the same north-south extinction pattern as here, just a few yards from the California-Mexico border.

"In the northern part of its range, humans have caused a lot of extinctions because humans have destroyed almost all of its habitat," says Parmesan. "Down at the southern edge of its range, in Baja, it's been getting warmer and drier and these little host plants have been drying up too quickly and the caterpillars have been starving."

"It's a classic case of a species that is squeezed between the forces of climate change driving it extinct in the south and human habitat destruction driving it extinct in the north," says Parmesan.

This year, something in the weather made them hatch two months too soon. When biologists checked this remote mesa top a few weeks later, they found that the few Checkerspots left no eggs and no caterpillars. With no next generation, a natural part of Southern California comes even closer to extinction.

Perils at a Preserve

Costa Rica's Monteverde is a land of rainbows because it's a land of rain and, even more, of mists and clouds. Its creatures and plants evolved over millions of years to live in and use the mist that blows at them.

Some 500 kinds of orchids get their only nutrients from its droplets, says Monteverde's biologist, Karen Masters.

"It carries all their food," she says. "Cloud and mist water have high concentrations of hydrogen ions, nitrates, ammonium ions… and so they are nutrient rich."

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