University of Colorado at Boulder Professor Gifford Miller said the study builds on his research group's previous findings that dozens of giant animal species went extinct in Australia roughly 50,000 years ago due to ecosystem changes caused by human burning. The new study indicates such burning may have altered the flora enough to decrease the exchange of water vapor between the biosphere and atmosphere, causing the failure of the Australian Monsoon over the interior.
"The question is whether localized burning 50,000 years ago could have had a continental-scale effect," said Miller, a fellow at CU-Boulder's Institute of Arctic and Alpine Research. "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."
A paper on the subject by Miller appears in the January issue of Geology. Co-authors include CU-Boulder's Jennifer Mangan, David Pollard, Starley Thompson and Benjamin Felzer of the National Center for Atmospheric Research in Boulder and John Magee of Australian National University in Canberra.
Geologic evidence indicates the interior of Australia was much wetter about 125,000 years ago during the last interglacial period. Although planetary and meteorological conditions during the most recent ice age caused Earth's major monsoons to waver, all except the Australian Monsoon were "reinvigorated" to full force during the Holocene Period beginning about 12,000 years ago, he said.
Although the Australian Monsoon delivers about 39 inches of rain annually to the north coast as it moves south from Asia, only about 13 inches of rain now falls on the c