Australia's most endearing species is already under threat from severe drought and loss of habitat as housing encroaches on woodland. The research showed that the level of toxicity in the leaves of eucalyptus saplings rises, and their nutrient content falls, when they were exposed to higher levels of carbon dioxide. "What currently may be good koala habitat may well become, over a period of not so many years at the rate that carbon dioxide concentrations are rising, very marginal habitat," Daily Telegraph quoted Ian Hume, Professor of Biology at Sydney University as saying.
"I'm sure we'll see koalas disappearing from their current range even though we don't see any change in tree species or structure of the forests,'' he stated.
Eucalyptus leaves have so little nutritional value that the animals have to sleep for 20 hours a day to conserve energy. The animals were also fussy eaters of Australia's more than 600 species of eucalypt trees and would only browse on the leaves of about 25. The koalas would be unable to adapt to the greater toxicity of gum tree leaves, said Prof Hume.
Forced to descend to the ground in search of trees with more nutritious leaves, the koalas would be more vulnerable to being hit by cars and attacked by predators such as dingoes and domestic dogs.