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May 14th 2008

Koalas at risk from climate change

The rising level of carbon dioxide pollution in the atmosphere is threatening the charismatic koala, by sapping nutrients from eucalyptus leaves, the favourite food of this Australian marsupial.

The scientists that uncovered this worrying effect also found that an increase in carbon dioxide causes toxicity levels in eucalyptus leaves to rise. While eucalyptus leaves are already highly toxic, an increase in toxicity could result in the leaves becoming unpalatable to koalas.

The effects of carbon dioxide on eucalyptus trees led scientists to suggest that at current levels of carbon dioxide emissions, the number of koalas in Australia could noticeably reduce over the next 50 years.

Currently, koalas produce an average of one young each year, but if their primary food source becomes less nutritious, this could fall to one young every three or four years.

While there are more than 600 species of eucalyptus in Australia, koalas only eat the leaves of about 25. If toxicity levels in the trees increased, koalas could find themselves with an even more limited diet.

The leafy diet of the koala does not provide much energy, but long periods of sleep, along with their relatively small brains, help compensate for this.