Scientists have warned that global warming is likely to reduce the health of the world's tropical species.
The team of scientists, from UCLA and the University of Washington, have also said that a little bit of warming may actually move certain organisms, particularly insects, in the high latitudes closer to their optimal temperature.
"In the tropics, most of the organisms we have studied, from insects to amphibians and reptiles, are already living at their optimal physiological temperatures," said Curtis Deutsch, UCLA assistant professor of atmospheric and oceanic sciences and co-author of the study.
"When warming starts, they do less well as they move toward the hottest end of their comfort range. Even a modest increase in temperature appears rather large to them and negatively impacts their population growth rates," he added.
According to Deutsch, the biodiversity of the planet is concentrated in tropical climates, where there is a tremendous variety of species.
"This makes our finding that the impacts of global warming are going to be most detrimental to species in tropical climates all the more disturbing," he said.
According to the study, the range of temperature tolerance that an organism has is largely dependent on how much temperature variability it experiences. In the tropics, the amount of temperature variability is very small and there is little difference between summer and winter.
To live in their environments, organisms in the tropics should have a relatively narrow tolerance for temperature change, while in the high latitudes, organisms should be able to tolerate a much wider variation in temperature.
In addition, what hurts the insects hurts the ecosystem.
Insects carry out essential functions for humans and ecosystems — such as pollinating crops and breaking down organic matter back into its nutrients so other organisms can use them.
For the short term, the impact of global warming will have opposing effects.
While in the tropics, warming will reduce insects' ability to reproduce; in the high latitudes, the ability of organisms to reproduce will increase slightly. But, if warming continues, the insects in the high latitudes would eventually be adversely affected as well. "
Our results imply that in the absence of any adaptation or migration by these populations in the tropics, they will experience large declines in their population growth rate," said Deutsch. "This could lead to a fairly rapid population collapse," he added.