Koalas are threatened by the rising level of carbon dioxide pollution in the atmosphere because it saps nutrients from the eucalyptus leaves they feed on. Carbon dioxide pollution is contaminating eucalyptus leaves, koalas' primary food source. Ian Hume, professor of biology at Sydney University, said he and his researchers also found that the amount of toxicity in the leaves of eucalyptus saplings rose when the level of carbon dioxide within a greenhouse was increased. Hume estimated that current levels of global carbon dioxide would result in a noticeable decrease in Australia's koala population in 50 years due to a lack of non-toxic leaves.
Out of more than 600 eucalyptus species in Australia, koalas will only eat the leaves of about 25, Hume said. Changing the toxicity levels in the trees could further reduce the varieties that koalas find appetizing, he said.
"Koalas produce one young each year under certain conditions, but if you drop the nutritional value of the leaves, it might become one young every three or four years," Hume said.
Eucalyptus leaves already have little nutritional value, he said, and koalas have adapted to their poor diet by sleeping to conserve energy.
Koalas basically sleep for 20 hours a day and then they've got four hours to do everything else.
Koalas had already disappeared from parts of Australia but remained plentiful in others and were unlikely to be wiped out by climate change. They already have been displaced from the most nutritious trees on the most fertile land by the spread of farms and suburbs, he said.
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