Do you know about shrinkage?
No, not the kind that happens in men's swimming trunks when it's cold, as we were taught in the classic Seinfeld moment.
In a quick inventory of climate change's impacts on the environment, a recurring theme emerges in our lakes, forests, Arctic ice coverage, animals and even the global gross domestic product: Shrinkage.
In a perspective piece for the journal Science, for example, Kaustuv Roy writes about the spectrum of animal species shrinking in response to global warming.
It follows the logic of Bergmann's rule: A controversial assertion that a species' body mass increases with latitude, or colder climes, while animals tend to be smaller in the tropics. Bigger animals have smaller surface to volume ratios and can more effectively conserve heat in cold environments, the rule states, while smaller animals with larger surface to volume ratios are better adapted to warmer environments because they can more effectively dissipate heat.
So as the world gets warmer, historical patterns dictate that animals will get smaller.
"Basically the premise is, if you look at a number of studies, there is a link between the environment, the temperature and the size of a species," Roy, a biologist at the University of California said in a phone interview.
For example, researchers studying the size of sheep on Scotland's Hirta island recently published a study in Science that was the first to establish a direct link between an animal's size and climate change.
The 20-year study showed that bigger sheep were more likely to survive the harsh, bitter winters of the 1980s. But as the winters warmed over the years, the genetic advantage to being bigger disappeared, resulting in smaller animals and reduced natural selection.
Roy also cites Israeli passerine birds as another example of global warming-induced shrinkage. Between 1950 and 1999, the body mass of Israeli passerine birds were observed to decline significantly in a study out of Tel Aviv University. In the meantime, minimum summer temperatures increased by an average of 0.26 C per decade during the second half of the 20th century.
Likewise, cod fish have also diminished in size over the past few decades, Roy said, as a result of another kind of pressure -- human harvesting.
"Humans are highly size-selective," he said. "We always take the big fish."
Before the collapse of Newfoundland's cod stocks in 1992, for example, stocks were abundant and the fish huge, said Roy, who lived and studied in Newfoundland in the late 1980s.
But since overexploiting the seas, cod have diminished in size, a biological response to human harvesting that happened quickly, over the course of just a few decades, he said.
"One thing we do know, is that the sizes of a species has gone down as a result of harvesting," Roy said.
But it's not only animals that are projected to diminish in size, their habitats are shrinking, too. In Africa, desertification and drier climates near Lake Chad are forcing farmers to drain the lake for irrigation purposes. What was once a lake of 25,000 sq. km. has been reduced to a mere 500 sq. km. in just 40 years.
Climate change is also expected to increase forest fires across the planet.
This year, Arctic sea ice cover shrunk to its second lowest level since satellite measurements began in 1979. Second only behind last year's record low.
Glaciers, while they've always grown and receded over time, are also shrinking at alarming rates. According to UN figures, the average rate of melting and thinning doubled between 2004 and 2006, among the 30 reference glaciers.
So despite what some contrarians may say, size does matter.
http://www.torontosun.com/life/green...99146-sun.html
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