WASHINGTON - Settlers who came to Australia 50,000 years ago and set fires that burned off natural flora and fauna may have triggered a cataclysmic weather change that turned the continent's interior into the dry desert it is today, say researchers.
Their study, reported in the journal Geology, supports arguments
that settlers changed the landscape of the continent with fire.
"The implications are that the burning may have changed the climate of the Australian continent by weakening the penetration of monsoon moisture into the interior," said Gifford Miller, of the University of Colorado at Boulder, who led the study.
The geological record shows the interior of Australia was much wetter 125,000 years ago. The last Ice Age changed the weather across the planet, but as the glaciers retreated 12,000 years ago the monsoons returned - except the Australian monsoon.
The Australian monsoon now brings about 1000mm of rain a year to the north but only about 130mm of rain falls on the interior. Miller's study suggests large fires could have altered the plant population to decrease the exchange of water vapour with the atmosphere, stopping clouds forming.
The researchers, working with John Magee of the Australian National University in Canberra, used computerised global climate simulations to show that if there were some forest in the middle of Australia, it would lead to a monsoon with twice as much rain as the present pattern.
Fossil evidence shows birds and marsupials that once lived in Australia's interior would have browsed on trees, shrubs and grasses rather than the desert scrub environment that is there today.
It also shows large charcoal deposits most likely caused by widespread fires, conveniently dating to the arrival of people.
People are also blamed for killing off 85 per cent of Australia's huge animals, including an ostrich-sized bird, a 7.5m lizard and a car-sized tortoise.
- REUTERS
