A new research has indicated that Koalas and other leaf-eating animals may be threatened because of climate change causing eucalyptus leaves to become inedible.
The research, carried out in Australia, saw eucalyptus leaves, which are the staple diet of Koalas, turning to leather.
Koalas and greater gliders depend entirely on eucalyptus leaves for food, while some other marsupials, including brushtail and ringtail possums and many wallaby species, feed extensively on the leaves.
Also, numerous insect species feed exclusively on eucalyptus leaves.
Scientists have reported mysterious declines in populations of greater gliders and brushtail possums in parts of Queensland in areas where the bushland remains in pristine condition, and where there are no apparent pressures from hunting, disease or other factors.
In fact, greater gliders have disappeared from places where they were numerous 20 years ago.
According to zoologist Jane De Gabriel, the falling nutrient levels in eucalyptus leaves could explain the population declines.
James Cook University researcher Ivan Lawler found through experiments in greenhouses that increased levels of carbon dioxide reduced the levels of nitrogen and other nutrients in eucalyptus leaves and boosted tanins, a naturally occurring chemical toxin.
As a result, the levels of protein in the leaves, essential to the survival of leaf-eating marsupials, fell sharply.
"The balance in the leaves shifts from nutrients to non-nutritional fibre. It eventually reaches a threshold when leaves are no longer tenable as a food source," said Dr Lawler.
"The food chain for these animals (koalas) is very finely balanced, and a small change can have serious consequences," he added.
According to Dr Lawler, eucalyptus leaves were already poor nutritionally, with low protein levels, requiring a koala to eat 700g a day to survive.
"With more carbon dioxide, animals need to eat more and more leaves to get their required protein levels," he said.
What De Gabriel found from her research in woodlands west of Townsville was that brushtail possums bred more frequently in areas of bushland with high levels of protein in the eucalyptus leaves. The breeding success rate was five times that of possums in areas with low protein levels.
"This suggests that in areas where nutrient levels are inadequate, animals will not be able to reproduce successfully," said De Gabriel.
The report concluded that the animals most at risk in Australia are those living at high altitudes in Queensland's wet tropics and in the Alps.