Randolph E. Schmid, Associated Press Yahoo News 10 Oct 08;
If you can't stand global warming, get out of the tropics. While the most significant harm from climate change so far has been in the polar regions, tropical plants and animals may face an even greater threat, say scientists who studied conditions in Costa Rica.
"Many lowland tropical species could be in trouble," the team of researchers, led by Robert K. Colwell of the University of Connecticut, warns in Friday's edition of the journal Science.
"The tropics, in the popular view, are already hot, so how could global warming harm tropical species? We hope to put this concern on the conservation agenda," Colwell said.
That's because some tropical species, insects are an example, are living near their maximum temperatures already and warmer conditions could cause them to decline, Colwell explained.
"We chose the word 'attrition' to emphasize slow deterioration," he said. "How soon that will be evident enough for a consensus is difficult to say."
But the researchers estimated that a temperature increase of 5.8 degrees Fahrenheit (3.2 Celsius) over a century would make 53 percent of the 1,902 lowland tropical species they studied subject to attrition.
That doesn't mean today's jungles will one day be barren, however.
"'Tis an ill wind that blows nobody any good. Some species will thrive," Colwell said. "But they are likely to be those already adapted to stressful conditions," such as weeds.
What of the others?
There are few nearby cooler locations for tropical plants and animals fleeing rising temperatures.
In the tropics in particular, going up rather than out may be an answer.
That's because tropical species with small ranges would have to shift thousands of kilometers north or south to maintain their current climatic conditions. "Instead," Colwell said, "the most likely escape route in the tropics is to follow temperature zone shifts upward in elevation on tropical mountainsides."
For example, moving uphill, the researchers said, temperature declines between 9.4 degrees Fahrenheit (5.2 C) and 11.7 degrees (6.5 C) for every 3,280 feet (1,000 meters). To get a similar reduction moving north or south, species would have to travel more than 620 miles (1,000 kilometers).
Of course moving won't work for everyone; species already living on mountaintops will have no place to climb.
The study provides an important illustration of the potential risk to tropical species from global warming, Jens-Christian Svenning of the University of Aarhus, Denmark, and Richard Condit of the Smithsonian Tropical Research Institute note in a commentary on the findings.
"These numbers suggest large risks," but are likely to be controversial because there remain large gaps in the knowledge of species' sensitivity to climate change, added Condit and Svenning, who were not part of the research team.
Meanwhile, a separate paper in Science reports that warming climate has already scrambled the ranges of small mammals in Yosemite National Park.
Ranges for some high-elevation mammals such as the alpine chipmunk have shrunk, while animals living at low elevations, such as the harvest mouse, have expanded their ranges into higher reaches, Craig Moritz of the University of California, Berkeley, and colleagues report.
Earlier this year a study of 171 forest species in Western Europe showed most of them are shifting their favored locations to higher, cooler spots. For the first time, research can show the "fingerprints of climate change" in the distribution of plants by altitude, and not only in sensitive ecosystems, said Jonathan Lenoir of AgroParisTech in Nancy, France.
His team found "a significant upward shift of species optimum elevation, the altitude where species are the most likely to be found over their whole elevation range."
Global warming sending tropical species uphill: study
Yahoo News 9 Oct 08;
Global warming is driving tropical plant and animal species to higher altitudes, potentially leaving lowland rainforest with nothing to take their place, ecologists argue in this week's issue of Science.
In a rare study on the impact of global warming in the tropics, University of Connecticut ecologist Robert Colwell and colleagues worked their way up the forested slope of a Costa Rican volcano to collect data on 2,000 types of plants and insects.
"Half of these species have such narrow altitudinal ranges that a 600-meter (2,000 feet) uphill shift would move these species into territory completely new to them," said a summary of their article released Thursday.
Many species would be unable to relocate at all, as most tropical mountainside forests have become "severely fragmented" by human activities.
Tropical lowland forests -- the warmest on Earth -- would meanwhile be challenged by the absence of replacement species. Flora and fauna unable to move uphill could also perish, unless it turns out they they can bear higher temperatures.
"Only further research can estimate the risk," the summary said, "but Colwell's report indicates that the impact of global climate change on some tropical rainforest and mountain species could be significant."
In another article, Science reports this week on a similar uphill trek by squirrels, mice and other small mammals in Yosemite National Park in California, one of the oldest wilderness parks in the United States.
Comparing a landmark 1918 study against fresh data about Yosemite's wildlife numbers, it found that small mammals have moved to higher altitudes, or reduced their ranges, in response to warmer temperatures.
"We didn't set out to study the effects of climate change," said Craig Moritz, a zoologist and integrative biology professor at the University of California at Berkeley who led the study.
"But the most dramatic finding in the Yosemite transect was the upward elevational shift of species," he said. "When we asked ourselves what changed, it hit us between the eyes -- the climate."
While such population movements have not altered Yosemite's biodiversity, Moritz's research team felt that rapid changes to the climate in less than a century could be a problem, a summary of the article said.
While half of the small mammal species at Yosemite have shifted their ranges, the other half has not. That means wildlife communities -- and the way in which species interact -- have changed, the summary explained.
If such change happens too fast, said James Patton, a member of the study, "elements of the (ecosystem) may start to collapse because a keystone element gets pulled out too quickly".
The study used as its starting point a detailed 1918 survey of Sierra Nevada wildlife by a Berkeley professor, when the snow-capped mountain range was under threat from gold mining and overgrazing.
