Climate change is reducing the body size of many animal and plant species - such as this Sambas stream toad (or Bornean rainbow toad), which was discovered earlier this year - including some which supply vital nutrition.
Credit: AFP/CONSERVATION INTERNATIONAL/File, Indraneil Das
PARIS: Plants and animals are reducing in size as a result of global climate change and it could have negative implications for food security, new research suggests.
From micro-organisms to top predators, nearly 45% of species for which data was reviewed grew smaller over multiple generations due to climate change.
The study, published in the journal Nature Climate Change, also warned that some of these organisms supply vital nutrition for more than a billion people already living near hunger's threshold.
The impact of rapidly climbing temperatures and shifts in rainfall patterns on body size could have unpredictable and possible severe consequences, said the researchers from the National University of Singapore.
"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."
Fossils reveal shrinkage
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% over a period of several thousand years. Mammals such as squirrels and woodrats also diminished in size, by about 40%.
Current warming more severe
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% 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% 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.
