Species in the Fast Lane: Speeding Up Growth and Metabolism

Climate change could jumpstart the metabolisms of tropical species

Earth Lion is a tropical chameleon. Photo: Richards Inyem

Metabolism is more than just what may be responsible for sluggishness or weight gain. In fact, it’s the basis of life, controlling everything from growth and reproduction to energy production and cell formation through a series of chemical reactions.

Air temperature can affect metabolism, especially for species that rely on the external weather to control body temperature. Ectotherms like reptiles and amphibians get lethargic when it’s cold and frisky when it’s warm.

New research published in the October 7 edition of Nature points out that global warming could be having an unsuspecting impact on metabolisms, especially in the tropics. Much concern over species has focused on the Arctic and mid to high latitudes, where shifts in temperature are most extreme.

The tropics are the center of Earth’s biodiversity. Image Credit: Aaron Gronstal

But the University of Wyoming-led team writes that species in the tropics (they studied ectotherms) will have greater absolute shifts in metabolic rates than Arctic species, even though the temperature difference in the tropics is smaller. This is due to the way metabolic rate increases.

The impact of climate warming on metabolic rate has never been quantified on a global scale, they write. “Here we show that estimated changes in terrestrial metabolic rates in the tropics are large, and are in fact far greater than those in the Arctic, even though tropical temperature change has been relatively small.”

So what’s the result? Higher metabolic rates mean these species will need to eat more, and thus be vulnerable to starvation unless food resources also increase. The more energy devoted to food could reduce reproductive capacity, while complex food webs could be severely impacted through more predation and herbivory. Insect-borne tropical diseases could increase.

“Because the tropics are the center 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,” they write.

Species may experience survival ‘tipping points’ at high temperatures

Some species seem to be taking climate change really hard, while others appear to be skating through it with little impact.

Moss campion is vulnerable to high temperatures in the Rockies. Photo: Ben K on Picasa

But looks can be deceiving. As temperatures continue to rise, resilient species may, too, find themselves under too much change to survive. A new study published in the recent journal Nature explores how Arctic and alpine species are coping.

Ecologists Daniel Doak from the University of Wyoming and William Morris from Duke University conducted a long term study of plants in the high altitudes of Colorado and New Mexico and along the Alaskan coastline. They found a complex set of responses to temperature increases. Survival was poor, in many cases along the most drastic extremes of the southern edges. But that negative response was somewhat offset by faster plant growth.

The scientists don’t believe that the two patterns cancel each other out. They found that extreme cold and warm years do not create the conditions for rapid growth.

They believe there’s quite possible a tipping point in which survival will overwhelmingly fall off. The tipping point will be different for each species and their responses will be sudden.

The lesson is that even if a species seems to be okay for the moment, there’s likely a breaking point at some higher, undetermined temperature.