The Japan Times, January 9, 1999
Bush fires set by early settlers burned out Australian animals, study says
WASHINGTON (Reuters) Australia's earliest human settlers probably wiped out many of the continent's big birds and other trademark animals by setting vast brush fires and changing the local ecology, researchers said Thursday.
Researchers said tests on the remains of one bird species showed it went extinct about 50,000 years ago, and indicated neither climate change nor hunting was to blame.
The best explanation was that big fires set by humans disrupted the brush on which the animals depended for food, said Gifford Miller of the University of Colorado at Boulder and his colleagues.
"Australia suffered a major loss of its large- and medium-size land mammals in the Late Pleistocene," a report stated in the journal Science. "All marsupials exceeding 100 kg, or 19 species, and 22 of 38 species between 10 and 100 kg became extinct, along with three large reptiles and the ostrich-size bird, called Genyornis newtoni."
"Two other large, flightless birds, the emu and the cassowary, survived."
They examined preserved eggshells left behind by the giant Genyornis and found evidence that the bird died out at three locations in Australia at about the same time. Other evidence suggested that climate changes at that time were modest, and insufficient to drive Genyornis to extinction.
"We suspect the systematic burning by the earliest colonizers - used to secure food, promote new vegetation growth, to signal other groups of people and for other purposes - differed enough from the natural fire cycle that key ecosystems were pushed past a threshold from which they could not recover," Miller said in a statement.
Studies of the bird's remains show it was a browser. Such animals, which include deer, eat a wide variety of plants, including leaves and bushes - the same plants that are destroyed in brush fires.
When such animals disappeared, so did the carnivores that ate them.
Australia had many large animals before humans arrived, including Genyornis, which was about the size of an ostrich, a hippopotamus-size relative of the wombat, a Volkswagen-size tortoise and a huge snake, 8 meters long.
Like the big animals that once roamed the Great Plains of North America, many disappeared soon after humans arrived on the scene.
Some scientists contended that overhunting, or perhaps climate change, was responsible. But Miller said there was very little evidence that people ate Genyornis. He said the case would be the same with the other large animals.
The findings may also reopen debate about what happened to America's big animals.
There were natural fires in Australia, and some plants depend on fires for their reproductive cycles. But Miller said the human-set fires would have exceeded that level.
"One possibility is that burning practices of the earliest human immigrants differed enough from that of the natural fire cycle to disrupt ecosystems across the semiarid zone," the researchers wrote.
"We also documented a change in vegetation at about that time. We believe what happened is that the browser's shrubs vanished," said University of Washington researcher Marilyn Johnson.
Bushes were replaced with desert scrub, she said.
Other studies have found evidence of large fires just after people first arrived on the Australian continent 60,000 years ago.
"There are sediment cores from mainland Australia where charcoal levels increased at about the same time that humans arrived on the continent," Johnson said.
AUSTRALIA'S EARLIEST human sealers probably wiped out many of the continent's big birds, including the pictured Genyornis, and other unusual animals, researchers at the University of Colorado reported Thursday. The Genyornis is illustrated as being attacked by an 8-meter-long giant lizard in this picture by Peter Trusler. REUTERS PHOTO