Is Global Warming Leading to Extinction?

July 18, 2005 — -- 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.

"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."

The mist's cooling moisture is vital to thousands of local animal species, like this captive glass frog, whose pumping heart you can see through its skin. Glass frogs also sing.

"This used to be a great place for listening to glass frogs at night," says Pounds. "You could hear them over the roar of the waterfall"

But not any longer. Since the late 1980s, this Cloud Forest preserve has been under a complicated attack from global warming. "Birds, reptiles, mammals… a variety of species have been affected," says Pounds.

Where Have All the Clouds Gone?

We first met American scientist Alan Pounds here 11 years ago when he was trying to figure out why Monteverde's famous Golden Toad and Harlequin frog had vanished.

He had begun to suspect something in the weather. And now, still living in his tiny house in the forest and crunching hard data that he and others have collected, he's got some answers.

After years of monitoring animal populations, tracking fluctuations in the mist and working with climatologists, he found the warmer temperatures are making the clouds form higher up. The clouds' base had lifted, making "them less effective in delivering moisture to the forest," says Pounds.

The normal brief dry spells, have been getting longer. And plotting the length of dry spells each year, parallel to the number of species that disappeared each year, he found they matched exactly.

"The patterns suggest quite strongly that the changes are climate-related," says Pounds.

Invasion of the Aggressors

The warmer temperatures attack different species differently. And scientists such as Pounds can't always tell exactly how it attacks any one species. Monteverde's missing frogs may well have succumbed to a fungus that clogs their permeable skin.

"We think changing climate is affecting the probability of outbreaks or helping certain diseases spread over the landscape, loading the dice for epidemic outbreaks," says Pounds.

But animals that don't get that disease -- birds, insects and reptiles -- also disappeared in the drier years. The reason might be because as the clouds move up the mountain, so do other more aggressive species.

Pounds showed us lizards and birds such as the long-beaked toucan.

"This is a toucan from further down the mountain but it's started moving up into the cloud forest," says Pounds. Its big beak is adapted to reach into nests of other species and steal eggs.

"There's a lizard," he showed us. "This is an example of a species that has moved up the mountain. It's increasing in abundance at this altitude and the species that used to be very abundant here? Now, we don't see them at all."

No Refuge at the Mountain Top

Such changes are occurring atop other tropical mountains also bathed in mist -- in Madagascar. Expeditions led by scientist Chris Raxworthy of the American Museum of Natural History, also find a number of animal species are scrambling upslope in tandem with the rising temperatures.

But even at the top of the mountain, there may be no safety. Scientists there find that three species of frogs, last seen in 1993, are now missing.

"All three of them were found at the very top of the mountain," says Raxworthy. "Perhaps they've gone extinct… when species get to the top of a mountain they have nowhere to migrate to, they have no option but to go extinct."

Species have started "falling off mountaintops," as scientists put it, in many countries.

Lower elevation species have another problem. As animals seek cooler ground -- up-slope or toward the global poles -- they often bump into human civilization. Multi-lane highways, giant malls, cities and other natural areas clear cut for human become unpassable for wild species.

Orchids in the Mist

It's not just animals affected by the temperature changes either. Plants, the basis of all animal life, struggle with global warming as we found back among the rich plant life of Costa Rica.

Two-thirds of Monteverde's plant species, including its orchids, never touch the ground because they're epiphytes -- plants that grow on top of other plants. So changes that affect one plant, may bring adverse effects to all the other plants that are supported by it.

Look closely at Monteverde's orchids, as American scientist Karen Masters does, and you see some already in serious trouble.

"I'm trying to mimic the mist frequencies of the 1970s, so I collect mist daily and apply it to each individual orchid," says Masters.

Half of the test-orchids in the forest get sprayed by Masters while the others get no mist except from the weather.

"We know mist frequency is declining here. They're probably not adapted to increasing periods of dessication, of dryness," says Masters. "I hate to say with certainty what the outcomes will be, so that's why I'm running the experiments."

But Masters says her results so far show in today's weather, some of her wild orchids -- and by implication thousands of other plant species here -- are stressed.

From around the world, scientists now report mammals, mollusks, grasses, trees are being disrupted in ways they would expect from global warming. Species are either trying for cooler ground or losing weight or thinning out -- and in effect throwing natural schedules out of sync.

Despair and Hope

The scientists are not telling us that the world is coming to an end, but that there will be change and increasing uncertainty about just exactly what that change is going to be. So what the scientists are telling us is that we've got to get ready, to adapt and to try to help all of life adapt.

But how could we even think about a problem so big? What do the scientists think and feel about what they have discovered? How do they live daily with the knowledge about what the rising temperature is doing to life on Earth?

"I see sometimes biologists that have been working at a site for a very long time and toward the end of their experiences, they become somewhat jaded, they become saddened, because they feel there's been this inevitable degradation of the forest or the species that they've come to know and love," says Chris Raxworthy.

"The Biosphere. That's the totality of life on the face of the Earth. It's a razor-thin membrane of living organisms," says Wilson. "That's our bubble, we live in that. Have we got any big risk in it? We got a lot of risk in it!"

"It's an urgent situation, but it's not a situation that should paralyze people with fear or with inaction," says Masters. "I am very optimistic that we will adjust. There's such an amazing groundswell, such an amazing movement by people around the world."

"If we continue business as usual, yes, I think life as we know it is going to change drastically," says Parmesan. "And we're going to have massive extinctions."

"This is a challenge that's one of the most daunting before humanity now," says Wilson. "It is also a magnificent challenge, that I think that people understand that they would want to be part of it."

The biologists are telling us if the average global temperature keeps going up it's not a question of if -- but how many -- more species will be lost.