Global warming isn't just a threat to polar bears in the rapidly warming Arctic, a new study says: Species in the tropics are beginning to feel the effects as well, and it will only get worse. Researchers surveyed more than 1,900 species of plants, insects, and fungi in a Costa Rica rainforest and came to the troubling conclusion that if world temperatures continue to rise as predicted over the next 50 years, half of those species will have to move to completely new territory to find an appropriate habitat. The situation is complicated for tropical species, says lead researcher Robert Colwell; shifting north or south doesn't bring significantly lower temperatures, so species will have to take up residence at higher altitudes to survive.

In the absence of mountainsides to serve as a cool refuge, those plants and insects that cannot face higher temperatures may disappear as it would require migrations of hundreds or even thousands of miles to find a suitable cooler climate—crossing habitats utterly changed by human impacts. "For lowland tropical species whose geographical range lies far from mountains, for example in the middle of the Amazon," Colwell says, "the prospect for extinction cannot be dismissed" [Scientific American].

The report, published in Science [subscription required], suggests that the treasured biodiversity of rainforest may be just as endangered as the icy splendor of the Arctic. Many of the insects and plants inhabit narrow ranges, and Colwell argues that some species

will have to move their ranges as much as 2,000 feet higher if the climate heats up by as much as 6 degrees, and that will put them into wholly new environments facing competition that evolution hasn't equipped them to face.... At the same time, species already living near [mountaintops] will find themselves with nowhere higher to move [San Francisco Chronicle].

Some experts disagree with his assessment, says Colwell, because of the region's ancient history.

"The current conventional wisdom even among scientists is that tropical species will be OK despite global warming because in ancient times -- 5 to 50 million years ago -- the climate was warmer and there were tropical forests," he said. "We argue this is not so clear. That there needs to be much more research done to see if this is the case," he said [Reuters].

And while researchers are busy figuring this out, Colwell suggests that it wouldn't be a bad idea to protect tropical mountainsides from development, just in case some species are looking for a new home. Related Content: 80beats: Should Humans Relocate Animals Threatened by Global Warming? 80beats: Plants "Climb" Mountains to Escape Global Warming