WASHINGTON — 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 study 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, warned in Friday's edition of the journal Science.
That's because some tropical species are living near their maximum temperatures already, and warmer conditions could cause them to decline, Colwell said.
The researchers estimated that a temperature increase of 5.8 degrees Fahrenheit 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.
"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 great distances 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 and 11.7 degrees Fahrenheit for every 3,280 feet. To get a similar reduction moving north or south, species would have to travel more than 620 miles.
Of course moving won't work for everyone; species already living on mountaintops will have no place to climb.