Koalas at Risk From Climate Change
The Associated Press, Discovery.com, May 7, 2008
Koalas are threatened by the rising level of carbon dioxide in the atmosphere because it saps nutrients from the eucalyptus leaves they feed on, a researcher said Wednesday.
Ian Hume, emeritus professor of biology at
Hume presented his research on the effects of carbon dioxide on eucalyptus leaves to the
The researchers found that carbon dioxide in eucalyptus leaves affects the balance of nutrients and "anti-nutrients" -- substances that are either toxic or interfere with the digestion of nutrients.
An increase in carbon dioxide favors the trees' production of carbon-based anti-nutrients over nutrients, so leaves can become toxic to koalas, Hume said.
Some eucalyptus species may have high protein content, but anti-nutrients such as tannins bind the protein so it cannot be digested by koalas.
Hume estimated that current levels of global carbon dioxide emissions would result in a noticeable reduction in
Out of more than 600 eucalyptus species in
"Koalas produce one young each year under optimal conditions, but if you drop the nutritional value of the leaves, it might become one young every three or four years," Hume said.
Hugh Tyndale-Biscoe, a marsupial physiologist, described Hume's predictions of declining koala numbers as speculative but credible.
Eucalyptus leaves already have little nutritional value, he said, and koalas have adapted to their poor diet by sleeping to conserve energy.
"It's a very precarious existence," Tyndale-Biscoe said. "They basically sleep for 20 hours a day and then they've got four hours to do everything else -- occasionally eat a leaf and maybe once a year go after another koala" to mate.
Tyndale-Biscoe said koalas had already disappeared from parts of