Animals in tropics will be hit hardest by climate change

Even though the Arctic is warming much faster than the tropics, the report says lizards, amphibians and other cold-blooded creatures living in equatorial regions will experience the greatest change in metabolic rates as the planet warms.

As their metabolism rate rises, they will need more food and are likely to lose more water through evaporation, said researcher Michael Dillon at the University of Wyoming and his colleagues, who predict widespread repercussions.

"Because the tropics are the centre of Earth's biodiversity and its chief engine of primary productivity, the relatively large effects of temperature change on the metabolism of tropical ectotherms may have profound local and global consequences," the scientists conclude in their report published in the journal Nature on Thursday.

Ectotherms depend on external heat sources, which explain why reptiles spend so much time basking in the sun.

The scientists say there is mounting evidence that even small temperature changes can push tropical organisms beyond their optimal body temperatures and cause substantial stress, while organisms in temperate and polar regions can tolerate much larger increases because they are already accustomed to large seasonal temperature swings.

"Just because the temperature change in the tropics is small doesn't mean the biological impacts will be small," co-author Raymond Huey at the University Washington said in an accompanying release. "All of the studies we're doing suggest the opposite is true."

Rising animal metabolic rates mean tropical creatures could require more food and oxygen, which could mean less time and energy for reproduction, the researchers say. "Metabolic rate tells you how fast the animal is living and thus its intensity of life," says Huey.

The researchers used nearly 500 million temperature readings from more than 3,000 stations around the world — including many in the Canadian Arctic — to chart temperature increases from 1961 through 2009. Then they calculated the effect of the rising temperatures on metabolism rates and concluded it is "in fact far greater" on creatures in the tropics than those in the Arctic.

"The expectation was that physiological changes would also be greatest in the north temperate-Arctic region, but when we ran the numbers, that expectation was flipped on its head," said Dillon, the report's lead author.

"Large effects of recent climate warming on metabolic rates are predicted for invertebrates, amphibians and reptiles in equatorial West Africa, the Caribbean and Central America, Ecuador, eastern equatorial Brazil and the Persian Gulf region," the report says.

Source: montrealgazette.com