BRENDAN TREMBATH: As firefighters around Australia gain control over bushfires which have killed two people and destroyed hundreds of homes, researchers are doing their bit to minimise fire risks.
Australian National University Associate Professor Geoff Cary is a project leader at the Bushfire Cooperative Research Centre.
He told Whitney Fitzsimmons what most urgently needs to be addressed.
GEOFF CARY: We can think about the various aspects to solving the bushfire problem in terms of three categories; controlling fuels and fire regimes, increasing the resistance of assets, such as houses, to damage from bushfires, perhaps moving assets away from the path of fires, not for houses but certainly for people.
Our work has looked mostly at controlling fuels and fire regimes. We looked at 499 houses affected by three of the largest bushfires on Black Saturday. We found that the amount of tree and shrub cover immediately around the house within about 40 metres of the house was really critical in determining whether the house would survive.
For example, houses that had a very high tree and shrub cover within 40 metres had a 70 per cent chance of being destroyed under those catastrophic conditions, whereas the probability of being destroyed if the tree and shrub cover was very low was as low as 30 per cent.
Other factors that determined the likelihood of house loss included how far away houses were in an upwind distance to trees and whether the house had a remnant native garden or a planted garden.
WHITNEY FITZSIMMONS: In your view, what have we learned from past events such as Black Saturday that can help us with the future?
GEOFF CARY: Well we've learned which particular land management practices will help us in saving houses. A combination of a lower tree and shrub cover around the house, some close prescribed burning if it's conducted recently, having neat and tidy gardens. All of these things combined will significantly reduce the probability of a house being destroyed.
WHITNEY FITZSIMMONS: What role is climate change playing in this?
GEOFF CARY: Climate change will affect bushfire occurrence in a number of ways. It will affect the rates of vegetation growth in some locations. In drier environments the vegetation will decline. In other locations the vegetation will become more available to burn under the warmer and drier environments.
It will certainly increase the ambient fire weather. Climate change is likely to affect the rates of ignitions of bushfires, particularly lightening ignitions, and there's some research that indicates that the rate of lightening ignition will increase across Australia.
WHITNEY FITZSIMMONS: The enquiries into bushfires have increased in size, particularly since the Black Saturday tragedy. But does this actually mean that they're more effective?
GEOFF CARY: I think this indicates a significant increase in the bushfire problem but also an increase in our understanding of the complexity of the problem and just the different dimensions, the different nature of the things that we need to deal with.
So it's recommendations and outcomes from these inquiries prompt us to think about the relative costs and effectiveness of these measures.
Some collaborative work between the Australian National University and the University of Wollongong looked at how much prescribed burning would be needed to halve the risk of bushfires to people and property. And we found that prescribed burning across 7 to 10 per cent of the landscape per year would be required to halve that risk in south eastern Australia and the cost associated with this to treat the fire prone forest and woodlands in south eastern Australia was in the order of $200 million a year.
BRENDAN TREMBATH: Associate Professor Geoff Cary from the Australian National University speaking to Whitney Fitzsimmons.