A shifting diet of two flightless birds inhabiting Australia tens of thousands of years ago is the best evidence yet that early humans may have altered the continents interior with fire, changing it from a mosaic of trees, shrubs and grasses to the desert scrub evident today, according to a University of Colorado at Boulder-led team.
Nearly intact eggshell of the extinct giant bird Genyornis newtoni, discovered near Port Augusta, South Australia in 2002. Note puncture hole from predator in upper left. The egg has been dated by both Optically Stimulated Luminescence (OSL) and Amino Acid Racemization (AAR) at 60,000 years, about 10,000 years before megafaunal extinction. Photo by G H Miller
7 Plant ecosystems in monsoonal Australia burn frequently through natural ignition by lightning strikes during the build up to the wet season, when dry lightning storms are common. But burning is also promoted by human ignition, from both traditional burning practices of Aboriginal Australians and governmental land managers. In Kakadu, a World Heritage Area east of Darwin, ecosystems have adapted to millennia of Aboriginal burning. Consequently, land managers strive to maintain the "natural" vegetation through prescribed burns in consultation with Aboriginal advisors. Land managers deliberately set this fire, 100 km south of Darwin. Photograph by Gifford H. Miller, Sept. 1998.
The unprecedented ecosystem disruption is now thought to have led to the extinction of Australias large terrestrial mammals, which disappeared shortly after humans colonized the continent about 50,000 years ago, said Professor Gifford Miller of CU-Boulders Institute of Arctic and Alpine Research. Scientists have shown there were no significant swings in the continents climate during that period, leading most to believe that humans had a hand in the extinctions through over-hunting, spreading disease or by altering the vegetation of the vast interior through systematic burning.
Using isotopic studies of fossil eggshells from both indigenous emus and the extinct, ostrich-sized Genyornis, a new study by Miller and colleagues publishing in the July 8 issue of Science magazine shows that the ecosystems flora changed swiftly and dramatically after humans arrived.
Gifford Miller | EurekAlert!
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