Australian Climate: Man Made

http://www.planetark.com/dailynewsstory.cfm/newsid/29201/story.htm

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 country's interior into the dry desert it is today, US and Australian researchers said on Tuesday.
Their study, reported in the latest issue of the journal, Geology, supports arguments that early settlers literally changed the landscape of the continent with fire.

"The implications are that the burning practices of early humans may have changed the climate of the Australian continent by weakening the penetration of monsoon moisture into the interior," Gifford Miller of the University of Colorado at Boulder, who led the study, said in a statement.

The geological record shows that the interior of Australia was much wetter about 125,000 years ago.

The last Ice Age changed the weather across the planet but monsoons returned as the glaciers retreated 12,000 years ago -- all except the Australian Monsoon.

The Australian Monsoon now brings about 39 inches (one metre) of rain annually to the north coast as it moves south from Asia, but only about 13 inches (33 cm) of rain falls on the interior each year.

Miller's study suggests that large fires could have altered the plant population enough to decrease the exchange of water vapor with the atmosphere, stopping clouds from forming.

The researchers, working with John Magee of Australian National University in Canberra, used computerized 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 current pattern.

Fossil evidence shows that 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 percent of Australia's huge animals, including an ostrich-sized bird, 19 species of marsupials, a 25-foot-long (7.5-metre) lizard and a Volkswagen-sized tortoise.

Some experts have suggested climate change caused by burning killed off these species, rather than direct hunting by human.