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What in the blazes? The fires to come |
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The Tuggeranong Valley aflame in the 2003 Canberra bushfires |
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Ecologist Dr Geoff Cary is working on better strategies to deal with Australian bushfires.
Photo courtesy of Belinda Pratten, Freeswimmers
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Bushfires capture an ambiguous standing in the minds of Australians. They are respected as part of the natural order of things in our tinder-box landscape, yet they are also a scourge, chasing people from their homes, swallowing property and lives. One scientist believes we are going to have to be much smarter about this animate element. He believes that in addition to warmer days, rising waters and parched earth, climate change will lead to many more bushfires than we've experienced in the past.
Dr Geoff Cary is a fire ecologist at the Fenner School of Environment and Society at the Australian National University who is using computer modelling to verify his beliefs. When he is asked to explain what he does one term crops up with regularity: "fire regime." This describes the frequency and intensity of bushfires in a particular area over a period of time.
The concept of fire regimes, Geoff explained, was pioneered in the mid 1970s by now Fenner School visiting fellow, Dr Malcolm Gill.
"Gill pointed out the importance of understanding the interval between fires, the intensity of the blazes and the seasons in which those fires occur," said Geoff.
"Since then, some researchers have sought out patterns of vegetation change in areas routinely burned and other scientists have attempted manipulative experiments, studying the effects of deliberately ignited blazes in a controlled area over long periods of time," he said. "Both of these efforts have tended to concentrate on the ecological effects of bushfires.
"However there's been much less study about what drives fire regime patterns in the first place. We have a good understanding at the national scale, but we don't have a long history of mapped fires to draw on and that's something we want, which has led to our work here at the Fenner School."
The computer model developed by Geoff and his colleagues is FIRESCAPE. This process-based computer model allows users to test the relationships between factors including fuel loads, fire behaviour, weather, ignition likelihood, and suppression capacity - the ability of humans to extinguish fires where and when desired.
"From these equations it's possible to compile a picture of fire regimes across complex landscapes and has since been tested with data from the Sydney basin, the ACT, southwestern Tasmania, Central Australia, and Montana in the United States," he said.
Geoff said the computer model builds up a picture of patterns in fire regime over a continuum of terrains and vegetation types, and over periods up to 100 years in length.
"The way we test the model is to run it in landscapes with the current climate and our current understanding of fuel and vegetation dynamics and the relationship to fire spread, then compare to a number of different-sized fires that you would get over a period.
"You can highlight areas of the landscape that are likely to have shorter intervals between fires which are the ones with a higher fire probability in the next few years. But whether that happens or not largely depends on the weather so we're averaging the results over much longer simulations.
"To test the affects of climate change we also introduced a 3.5 degree increase in temperature, which is about the middle of what we might expect," he said. "We then increased rainfall by a fifth and decreased rainfall by a fifth, as it's uncertain how global warming will influence precipitation.
"The interesting thing was that four out of five of those models responded in the same way: with increased areas burned in the study areas, irrespective of whether they were wetter or drier, gave us a consensus across the models."
In other words, Geoff is confident that a warmer planet will lead to more persistent and intense bushfires in forested systems around the world.
As fires occur more often, they are going to become increasingly difficult to extinguish, especially the lower intensity fires. If these fires are not dealt with quickly, the likelihood is that they will burn for longer periods, which increases the chances of them continuing to burn when severe weather occurs.
Faced with this prospect, Geoff argues that emergency services and other fire management personnel would be best to focus on rapid responses, extinguishing hot spots while they are still relatively small.
"I don't dismiss other forms of fire control, such as prescribed burning and the creation of containment lines around large fires but see these as part of a coordinated strategy that has early and rapid response as its major component," he explained. "None of these measures will prevent fires altogether, so people need to consider where they wish to live and measure the risks.
"Fires are a part of the natural ecosystem in Australia, they are part of the landscape so we need to be more thoughtful about where we build our assets and how we maintain our properties during fire seasons," Geoff concluded.
Author: Simon Couper
ANU Reporter the magazine of The Australian National University.
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Bushfires are naturally stored solar energy that is out of control. Native Australian trees convert sunlight into oils that get stored in leaves and end up burning like petrol.
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Each year 'disaster-level' bushfires (where the total insurance cost of the event was more than $10 million) cost Australia an average of $77 million.
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The NSW Rural Fire Service estimates that 94% of bushfires are started by humans. Half of these are a result of a burn-off that gets out of hand, and an increasing number are a result of arson. Other man-made reasons include spot fires caused by burning embers being blown away from buildings already burning, spark from power lines, sparks from mechanical sources, cigarette butts thrown out of cars, camp fires, etc.
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The Canberra bushfires of 2003 caused severe damage to the region. After burning for a week around the edges of the ACT, the fires entered the suburbs of Canberra on 18 January 2003. Over the next ten hours, four people died and more than 500 homes were destroyed or severely damaged.
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