Global warming on Animals

Cold-blooded and other animals that are unable to regulate their internal temperature may have a hard time tolerating global warming, according to an analysis by biologists from the University of California, Berkeley, and San Francisco State University.

A meta-analysis of studies that measured the ability of animals to deal with extremes of heat and cold found that, on average, most ectotherms are not very flexible. Terrestrial ectotherms, such as lizards and insects, are even less adaptable than fish and crustaceans, they found.

As Earth warms, these animals will be “living at temperatures much closer to their limit, ” said the study’s lead author, Alex Gunderson, a postdoctoral fellow at UC Berkeley and SF State’s Romberg Tiburon Center. This means that they are less likely to be able to survive yearly temperature swings, which themselves may become more extreme with climate change.

“Because animals have some ability to acclimate to higher temperatures, scientists hoped that they might be able to adjust their physiology to keep up with global warming, ” he said. “We found by compiling these data in the first large-scale study of hundreds of different animals that the amount they can actually adjust is pretty low. They don’t have the flexibility in heat tolerance to keep up with global warming.”

As a result, these animals have limited options as temperatures increase worldwide, he said. They can either move northward or to higher and cooler elevations, alter their behavior to spend more time in the shade, or evolve more thermal tolerance than they have today. Global temperature averages are rising so fast, however, that animals may not have time to evolve the physiological ability to tolerate higher heat.

“Our results suggest that their ability to acclimate to increasing temperatures will not buffer them from the changes that are occurring and that they are going to have to depend on behavioral or evolutionary change to persist, ” Gunderson said.

He and co-author Jonathon Stillman, a UC Berkeley assistant adjunct professor of integrative biology and SF State professor of biology, will publish their analysis online May 20 in the Proceedings of the Royal Society B. The study was funded by the Berkeley Initiative for Global Change Biology and SF State.

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