Aboriginal burn-off theory hosed down
TRADITIONAL THEORY SUGGESTS THAT Australian Aborigines have regularly burned-off the bush as a method to manage the landscape over the last 50,000 years. But an analysis of fossilised charcoal now contests that idea.
The new research suggests that Australia’s bushfire history can be explained by climate change and natural fire patterns, and that fires didn’t increase when Aboriginal people first arrived about 50,000 years ago.
“The [European settlers] made these grand assumptions about the Aborigines… which now we can see weren’t true,” says Dr Scott Mooney, a palaeontologist from the University of New South Wales.
Burn-offs or small, cool fires were thought to be used by Aboriginal people both for hunting and for the prevention of larger fires. They raze grass and other fuels, ideally eliminating the chances of a larger fire igniting. Early European settler records show that Aboriginal mobs were familiar with fire. They wrote about patches of smoke regularly appearing in the distance in certain times of the year.
Scott’s team examined and dated ancient swamp samples from 223 sites in Australia, Papua New Guinea, Indonesia and New Zealand, to determine the amount of charcoal present. The results hinted that bushfires raged through Australia 70,000 – 28,000 years ago, then decreased until 18,000 years ago, at the height of the last ice age. About 200 years ago they dramatically increased again, coinciding with European settlement.
The findings, published in the latest Quaternery Science Reviews, suggest that Australia’s fire history was more consistent with global fire and climate change than Aboriginal influence. “Fires are linked to environmental trends not to the activities of Aboriginals,” Scott says.
However, Dr Scott Heckbert an environmental economist with CSIRO Ecosystem Sciences in Darwin argues that charcoal records may not be the best way to study historical burnoffs as the smaller spot fires lit by Aborigines might not always result in much charcoal. He adds that most Australian plants wouldn’t be distributed around the country the way that they are now if people hadn’t burned-off the land through history.
Dr Gavin Prideaux, a palaeontologist from the Flinders University in Adelaide, also believes the new study placed too much emphasis on charcoal records: “It’s an important piece of evidence, but it’s not the only piece of evidence.”
Isotope records (variation in the different weights of chemicals that reveal key information) about an animal’s diet can also be useful evidence for fire history, he adds. “Isotope records from fossilised eggs belonging to the Genyornis [the extinct giant thunderbird] show that something changed in their diet that led to extinction 50,000 years ago. The change of diet happened to coincide with humans coming to Australia,” says Gavin. “Fire currently seems to be the most plausible explanation for the shift in vegetation.”
Moreover, there are other explanations for the increase in charcoal after European settlement, such as the relocation of Aboriginal people to settlements and urban areas, Gavin adds. “The devastating bushfires from the last two centuries took place because Aborigines lost access to their landscape. They were no longer starting these smaller fires.”