Jun 29, 2009, 11:41 GMT
Sydney - The idea of Australia is inseparable from the sight, the smell and even the taste of its eucalyptus trees.
Kangaroos shade beneath them, koalas munch their leaves, and when Australians go out bush, in the words of the song, it's to be among the gum trees.
There are over 700 species and they are in super-abundance in the wild. No problem there.
In farming country though, it's a different matter. Researchers at the Australian National University (ANU) warn that landscapes in which the gum trees dot the fields are under threat.
'In our lifetime, we'll already see a very different landscape,' ANU ecologist Joern Fischer said. 'When you drive through there in 30 years from now, you would have a lot more dead trees standing up, or just not being there any more.'
Most agricultural land is given over to sheep and cattle. Fertilizers are used to make the grass grow. The animals spend most of their lives in the one field.
Fischer explained that continuous grazing means that most saplings never grow into trees. Instead, they are stifled by the grass, trampled and killed.
'We're finding that at least half of grazing lands are not regenerating with trees under status-quo management,' he said.
Fischer predicts that the future is one of treeless plains - unless farming practices change and there is a shift to rotational grazing.
When plots are left fallow for a few years, saplings can reach maturity, because they don't compete with dressed grass and they don't get trampled to death when they are young.
The difficulty is that productivity is lost with rotation and, currently, there are not mechanisms to compensate the landowner for shifting away from continuous grazing.
The ANU study is published in the US-based journal Proceedings of the National Academy of Sciences.
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