SAN FRANCISCO, June 12 (Xinhua) — Two U.S. researchers have foreseen dramatic population declines in Mexico, Central America, Africa, India and other tropical locales due to climate change.

Solomon Hsiang, Chancellor's Associate Professor of Public Policy at the University of California, Berkeley, and Adam Sobel, a professor of applied physics and math at Columbia University, suggest that global warming by just 2 degrees Celsius is likely to force some tropical plant, animal and human populations to relocate hundreds of kilometers from their current homes.

Earth's temperature rise of average 2 degrees this century is considered "optimistic" compared to business-as-usual forecasts.

Using a model to demonstrate how climate dynamics in the tropics can magnify the consequences of warming as it is experienced on the ground, the pair conclude in a research published in the latest issue of journal Scientific Reports that even small changes can have dramatic impacts.

"We're not making specific predictions about migration patterns of individual species, but the geophysical constraint is that, as the tropics get hotter, you'll have to go far, essentially leaving the tropics, to cool off," said Sobel. And because the tropics are uniformly hot, when things get hotter by a small amount, populations will have to move far to find relief.

While the researchers describe climate-related displacements in the tropics as "an almost complete evacuation of the equatorial band" that could impact ecosystems as well as human well-being, Hsiang explains it with an analogy: "Imagine you have a fixed budget you can spend on your apartment and rents are the same throughout your entire neighborhood. If all the rents go up, even by just a little bit, you might have to move very far to find a new place you can afford."

"We know that people and species of all kinds move for all kinds of reasons, not just to stay at the same temperature," said Sobel. "At the same time, the uniformity of tropical temperatures is a basic fact about the temperature structure of Earth, and still will be as the climate changes."

The authors report that some oceanic and continental populations would have to move as far as 1,000 miles, about 1,600 kilometers, or more to stay within their "temperature budget."

Simulations suggest the cooler edges of the tropics could get crowded, where populations might theoretically climb by 300 percent or higher. At those densities, disease and conflict over resources, among other issues, would bring their own complications.

Cautious in applying their findings to human populations, since moving is only one of many strategies humans will use to cope with warming, the two researchers note that extraordinary human migrations cannot be ruled out.