Koalas get more than 90 per cent of their water from eucalyptus leaves. Eucalyptus leaves - which koalas depend on for survival - are being destroyed by abnormally high levels of greenhouse gases. Scientists warned early in 2008 that increased levels of carbon dioxide in the atmosphere were reducing nutrient levels in the leaves, and also boosting their toxic tannin content.{gallery}thirsty_koalas:::1{/gallery}
That has serious implications for koalas and other marsupials that eat only, or mainly, the leaves of gum trees. These include a number of possum and wallaby species. "What we're seeing, essentially, is that the staple diet of these animals is being turned to leather," said Bill Foley, a science professor at the Australian National University (ANU) in Canberra. "This is potentially a very significant development for the future of some marsupial populations. Life is set to become extremely difficult for these animals."
Climate change could help to explain decreases in the numbers of brushtail possums and greater gliders (a large possum) in certain parts of Queensland where none of the usual factors - disease, hunting, loss of habitat - appears to be to blame. Jane De Gabriel, a zoologist at ANU, reported that brushtail possums had been found to breed more prolifically in woodland areas where the protein levels in eucalyptus leaves were high. This suggests that in areas where nutrient levels are inadequate, animals will not be able to reproduce successfully. What follows are extinctions of wildlife populations.
Like koalas, greater gliders feed only on eucalyptus leaves. Greater gliders have disappeared from some habitats where they were abundant 20 years ago. Brushtail possums, ringtail possums and many wallabies rely on the leaves as the major component of their diet. Ivan Lawler, a researcher at Queensland's James Cook University, found that when there was more carbon dioxide in the atmosphere, the levels of nitrogen and other nutrients fell.
With more carbon dioxide, animals need to eat more and more leaves to get their required protein levels.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. The food chain for these animals is very finely balanced, and a small change can have serious consequences." WWF Australia warned recently that rising temperatures threatened numerous Australian native species, including the tree frog, the hare kangaroo, the tiny tree kangaroo and the greater bilby.
In a 2008 report WWF said that such creatures - already endangered as a result of wide-scale land clearing and the introduction of exotic predators - could be pushed into extinction by climate change and its knock-on effects.