Climate change spawns the incredible shrinking ant

Reuters 16 Oct 11;

HONG KONG Oct 17 (Reuters) - Plants and animals are shrinking because of warmer temperatures and lack of water, researchers said on Monday, warning it could have profound implications for food production in years ahead.

"The worst-case scenarios ... are that food crops and animals will shrink enough to have real implications for food security," Assistant Professor David Bickford, of the National University of Singapore's biological sciences department, said.

Bickford and colleague Jennifer Sheridan trawled through fossil records and dozens of studies which showed that many species of plants and creatures such as spiders, beetles, bees, ants and cicadas have shrunk over time in relation to climate change.

They cited an experiment showing how shoots and fruit are 3 to 17 percent smaller for every degree Celsius of warming in a variety of plants.

Each degree of warming also reduces by 0.5 to 4 percent the body size of marine invertebrates and 6 to 22 percent of fish.

"Survival of small individuals can increase with warmer temperatures, and drought conditions can lead to smaller offspring, leading to smaller average size," they wrote in their paper which was published in the journal, Nature Climate Change, on Monday.

"Impacts could range from food resources becoming more limited (less food produced on the same amount of land) to wholesale biodiversity loss and eventual catastrophic cascades of ecosystem services," Bickford wrote.

"We have not seen large-scale effects yet, but as temperatures change even more, these changes in body size might become much more pronounced - even having impacts for food security." (Reporting by Tan Ee Lyn; Editing by Nick Macfie)

Climate change downsizing fauna, flora: study
Marlowe Hood AFP Yahoo News 17 Oct 11;

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 released Sunday.

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 far greater than during this so-called Palaeocene-Eocene Thermal Maximum (PETM).

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," 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 one 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 in girth 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, goshawks and gulls -- and mammals such as soay sheep, red dear and polar bears, have also trended towards less bulk.

Some of the most worrying changes are at the bottom of the food chain, especially in the ocean, where tiny phytoplankton and calcium-building creatures are dwindling in size due to acidification and the reduced capacity of warmer water to hold oxygen and nutrients.

Carbon pollution has probably locked in an additional 1.0 C increase in average global temperatures, and continued emissions of greenhouse gases could push up the thermometre another 4.0 to 5.0 C (7.4 to 9.0 F) by centuries end, according to the UN's Intergovernmental Panel on Climate Change (IPCC).

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."

The study is published in the peer-reviewed journal Nature Climate Change.

Animals Shrink as Earth Warms
Wynne Parry LiveScience.com Yahoo News 17 Oct 11;

As global temperatures rise this century, the result of human-caused climate change, many living things will shrink, thanks to a host of changes in the environment, as well as the direct effects of warming, two researchers write.

If everything were to shrink at the same rate, this wouldn't be a problem. Smaller plants would feed smaller fish that would feed smaller sharks, for example. However, it appears that organisms don't all react at the same rate, so change is likely to throw ecosystems out of whack, putting some species at risk of extinction, according to Jennifer Sheridan and David Bickford of the National University of Singapore.

This isn't a new phenomenon; during past periods of natural global warming, beetles, bees, spiders, algae called diatoms, pocket gophers and woodrats have shrunk, according to fossil evidence. For example, the burrows dug by invertebrates, including beetles, bees and spiders, during a warm spell about 56 million years ago, show the creatures shrank by 50 to 75 percent, the researchers write in a study published on Oct. 16 issue of the journal Nature Climate Change.

Some modern shrinkage is expected to come about indirectly. For example, an increasing acidity in the ocean — caused by increased carbon dioxide in the atmosphere — interferes with some organisms' ability to build their calcium carbonate shells or skeletons (such as corals, scallops and oysters). Acidification also decreases growth rates among phytoplankton, the tiny plants that float in the ocean, and this has implications for the food chains that depend on them. [Colorful Creations: Gallery of Incredible Coral]

Plants were expected to thrive on the excess carbon dioxide humans have expelled into the atmosphere, because they use it to create sugars by photosynthesis. However, things have not played out this way over the past century. Plant growth is highly dependent on water, and while climate models predict that some areas will get wetter and others drier over the coming decades, many places are expected to experience higher variability in rainfall. This means longer dry periods even in wetter regions, which will ultimately reduce growth, according to the authors.

Cold-blooded animals — most of the animals on Earth — are directly affected by changes in temperature, which increase their metabolic rates. This means they need more food to maintain their body sizes, or shrink. Temperature also affects cold-blooded creatures by amping up their development rates, so the animals reach maturity at smaller sizes. Other research has explored how this plays out in copepods, tiny crustaceans that play an important role in marine food chains.

It is established that among warm-blooded animals, a colder climate means a larger body size, because larger animals are better able to conserve their body heat, and there is evidence that size decreases in warmer regions. For humans, changes in organism size could have a direct effect on our food supply, for instance, through crops and fisheries.

There are exceptions: Climate change is expected to increase the growing and feeding season in high-latitude places, and hence allow organisms to get bigger. (An exception to the exception: Polar bears are shrinking along with the Arctic sea ice upon which they live.) Also, animals with broad diets may be able to compensate for shrinking meals by shifting their diets.

"Continued global warming is likely to favor smaller individuals, and we predict that organism size will continue to decrease over the century," Sheridan and Bickford write.