The Canberra fires of 2003: a pine planataion on the edge of the Brindebella Ranges ignites
Credit: SMH
Whether or not humanity in general is exacerbating global warming and thus intensifying the droughts that plague the Australian continent - the driest after Antarctica - it's clear Australians themselves are contributing to their water shortage. The country's most economically important river system, the Murray-Darling, which drains much of Queensland and New South Wales, is drier now than it has been at any time in recorded history, its feeble flow the result of drought and voluminous withdrawals for farms, cities and reservoirs.
Some Australians further narrow the culprit to 'Big Irrigation': three water-intensive crops - cotton, rice and sugar - together account for about a third of the country's agricultural water consumption. The Murray-Darling basin's rice farms collectively use almost as much water as all of Australia's 20 million people, and some argue that Australian farmers should grow less thirsty produce. At any rate, tying up more and more water in water-intensive agriculture makes the rest of the place drier and more prone to burning.
But are global warming, increased drought, and recent human activity really the most important factors in making Australia increasingly prone to fire? Some ecologists have argued, on the contrary, that Australia is fire-prone chiefly because Australia's Aborigines made it so. In books such as The Future Eaters by moted biologist Tim Flannery, former director of the South Australian Museum in Adelaide, and The Burning Bush by Stephen Pyne, an environmental historian at Arizona State University in Tempe, USA, the idea is advanced that Aboriginal practices in place for tens of thousands of years were what really transformed the land into a fire-dependent ecosystem.
According to the hypothesis, Aborigines practised relentless, widespread burning in Australia for millennia - to drive game, clear land, forge pathways, and encourage new growth. The frequent burning would have eliminated shade-loving plants and favoured fire-loving, Sun-worshiping eucalypts.
The latter have developed specialised, enlarged woody growths called lignotubers, which can store nutrients and water in the earth, out of the reach of fire. If a tree is destroyed by fire, the lignotubers can send up new shoots almost immediately. In addition, the layered bark of the eucalypt forms a protective shield, which burns off in successive layers like the heat shield of a spaceship on re-entry. So, the argument goes, over many aeons, a self-reinforcing, dynamic process emerged: people burned the land, eucalypts thrived, people burned some more.
The hypothesis has two major practical implications for today's Australia: modern agriculture, by eliminating fire from its toolbox, has inadvertently increased the risk of massive fires by allowing fuel to accumulate through the years. Thus, to reduce the risk of large fires, smaller ones should frequently be set.
In favour of the hypothesis, some Aborigines are known to have practised "fire-stick farming" in some regions - purposeful, periodic clearing of large areas to manipulate the land for their own purposes. But opponents of the hypothesis counter that ascribing the evolution of a fire-prone ecology solely to the hand of fire-wielding humans is too simplistic.
Re-examining the early written records of the first European explorers in Australia, Rod J. Fensham of the Queensland Herbarium in Toowong found that although Aboriginal burning was prevalent along Queensland's coast, it was infrequent inland. Most of the early accounts of Aboriginal fire use, moreover, were written during a tumultuous era. Aborigines were losing their land, becoming exposed to new diseases, and running into conflicts with Europeans. The fires the explorers saw may not have been set to manage the land, but rather to protect Aborigines from European intruders, or perhaps signal the newcomers' presence to others.
