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Climate change causing reduction in sizes of animals and plants: study.

Summary: Climate change is reducing the body size of many animal and plant species, including some which supply vital nutrition for more than a billion people already living near hunger's threshold, according to a study published Sunday in the journal Nature Climate Change.

PARIS Paris, in Greek mythology
Paris or Alexander, in Greek mythology, son of Priam and Hecuba and brother of Hector. Because it was prophesied that he would cause the destruction of Troy, Paris was abandoned on Mt.
: Climate change is reducing the body size of many animal and plant species, including some which supply vital nutrition for more than a billion people already living near hunger's threshold, according to a study published Sunday in the journal Nature Climate Change.

From micro-organisms to top predators, nearly 45 percent of species for which data was reviewed grew smaller over multiple generations due to climate change, researchers found.

The impact of rapidly climbing temperatures and shifts in rainfall patterns on body size could have unpredictable and possible severe consequences, they warned.

Previous work established that recent climate change has led to sharp shifts in habitat and the timing of reproductive cycles. But impact on the size of plants and animals has received far less attention.

Jennifer Sheridan and David Bickford at the National University of Singapore looked at scientific literature on climate-change episodes in the distant past and at experiments and observations in recent history.

Fossil records, they found, were unambiguous: Past periods of rising temperatures had led both marine and land organisms to became progressively smaller.

During a warming event 55 million years ago -- often seen as an analogue for current climate change -- beetles, bees, spiders, wasps and ants shrank by 50 to 75 percent over a period of several thousand years.

Mammals such as squirrels and woodrats also diminished in size, by about 40 percent.

The pace of current warming, though, is much greater than climate change during the so-called Palaeocene-Eocene Thermal Maximum.

It, too, has begun to shrink dozens of species, the study found.

Among 85 examples cited, 45 percent were unaffected. But of those remaining, four out of five had gotten smaller, while a fifth got bigger.

Some of the shrinkage came as a surprise. "Plants were expected to get larger with increased atmospheric carbon dioxide carbon dioxide, chemical compound, CO2, a colorless, odorless, tasteless gas that is about one and one-half times as dense as air under ordinary conditions of temperature and pressure. ," but many wound up stunted due to changes in temperature, humidity and nutrients available, the researchers said.

For cold-blooded animals -- including insects, reptiles and amphibians - the impact is direct: experiments suggest that an upward tick of 1 degree Celsius translates into roughly a 10 percent increase in metabolism, the rate at which an organism uses energy. That, in turn, results in downsizing.

The common toad, for example, has measurably shriveled shriv·el  
intr. & tr.v. shriv·eled or shriv·elled, shriv·el·ing or shriv·el·ling, shriv·els
1. To become or make shrunken and wrinkled, often by drying:
 in girth GIRTH., A girth or yard is a measure of length. The word is of Saxon origin, taken from the circumference of the human body. Girth is contracted from girdeth, and signifies as much as girdle. See Ell.  in only two decades, along with some tortoises, marine iguanas and lizards.

Overfishing has been blamed for decreased body size in both wild and commercially harvested aquatic species, threatening the key source of protein of a billion people around the world, mainly in Africa and Asia.

But experiments and observational studies have shown that warming waters play a role as well, especially in rivers and lakes.

Birds -- including passerines passerines

birds belonging to the order Passeriformes.
, goshawks and gulls -- and mammals like soay sheep, red dear and polar bears, have also trended toward less bulk.

Some of the more worrying changes are at the bottom of the food chain, especially in the ocean, where tiny phytoplankton phytoplankton

Flora of freely floating, often minute organisms that drift with water currents. Like land vegetation, phytoplankton uses carbon dioxide, releases oxygen, and converts minerals to a form animals can use.
 and calcium-building creatures are dwindling in size due to acidification acidification

a technology used by processors to preserve foods by adding acids (such as acetic, citric, phosphoric, propionic and lactic acid) and thereby reduce the risk of growth of harmful bacteria.
 and the reduced capacity of warmer water to hold oxygen and nutrients.

Carbon pollution has probably locked in an additional 1 C increase in average global temperatures, and continued emissions of greenhouse gases could push up the thermometer another 4-5 C by centuries end, according to the U.N.'s Intergovernmental Panel on Climate Change “IPCC” redirects here. For other uses, see IPCC (disambiguation).
The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment
.

Because warming is occurring at unprecedented rates, "may organisms may not respond or adapt quickly enough," especially those with long generation times, the authors noted in an email.

"We do not yet know the exact mechanisms involved, or why some organisms are getting smaller while others are unaffected," they added. "Until we understand more, we could be risking negative consequences that we can't yet quantify."

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Publication:The Daily Star (Beirut, Lebanon)
Date:Oct 18, 2011
Words:671
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