Climate Change Too Fast for Ectotherms?

Ecotherms like reptiles, amphibians and fish are normally able to adapt to changes in the climate, and have done so in the past, but this time around climate change may be moving too fast for these animals to keep up, a new study suggests.

Many animals can adapt to a warming world by modifying the function of their cells and organs in order to compensate for such environmental shifts. But with the overall global temperature expected to climb 3.6 degrees Celsius (38.5 Fahrenheit) by the end of the century, along with increased temperature fluctuations, ectotherms especially would have to be able to function across a broader range of conditions.

That's because ectotherms, which make up more than 90 percent of all animals, rely on external sources of heat to control their body temperature. Therefore, they are heavily influenced by environmental temperatures, where rapid human-caused climate change could present them with some huge challenges.

"It is important that animals maintain the right balance between the large number of physiological functions despite environmental fluctuations. An increase in temperature that leads to changed reaction rates can upset that balance and cause the decline of individuals and species," lead study co-author Professor Frank Seebacher, from the University of Sydney in Australia, said in a statement.

Researchers studied 40 years of published data to determine how these cold-blooded animals altered their biological functions in response to sudden fluctuations in environmental temperatures. According to the study, the physiological rates of ectotherms, such as heart rate, metabolism and locomotion, had already increased in the past 20 years alone along with rising temperatures.

Such a direct impact could spell disaster for many species. For example, Seebacher notes, if an animal's metabolism or cardiovascular system can't deliver energy and oxygen to muscles due to rising temperatures, it can't hope to forage for food, migrate or interact with other individuals. A warming world would threaten a species' very survival, and cause a domino effect throughout the rest of the ecosystem.

"The overall trend in the last 20 years has been to increased physiological rates," Seebacher said, "and we predict that this would continue to increase with increasing temperature."

The findings were published in the journal Nature Climate Change.

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