“In most bioregions, prescribed burning is likely to have very little effect on the subsequent extent of unplanned fire, and even in regions where leverage occurs, large areas of treatment are required to substantially reduce the area burned by unplanned fire,” according to the study, published in the Journal of Biogeography.
The Sydney Basin, which includes the Blue Mountains, was one of the four areas where controlled burns had an impact over the 1975-2009 period studied. But even there, to limit wildfire area burnt required conducting hazard-reduction burns of three or four hectares.
Interestingly, in all regions studied, extreme weather was a stronger predictor of risk – up to ten times – than the extent of past fires.
While much of south-eastern Australia had a moderately warmer than average winter, temperatures have shot up in October, which many centres likely to challenge heat records for the month. The El Nino influence is also beginning to be felt, with the shifting wind patterns triggering a reduced rainfall outlook for much of eastern Australia, adding to the fire threat this season.
Shane Fitzsimmons, Commissioner of the NSW Rural Fire Service, said controlled burning was just one tool available to reduce bushfire risk.
Since about 90 per cent of homes lost to fires are the result of ember attacks, the onus rests largely with people preparing a defendable space around their residences, and doing all they can to remove combustible material in gutters and next to their houses, he said.
Ross Bradstock, director of the University of Wollongong’s Centre for Environmental Risk Management of Bushfires and another of the study’s authors, said the condition of forest fuels within about one kilometre from homes appears to be a crucial factor in determining risks.
Hazard-reduction fires near homes, though, is costly in terms of resources needed to ensure blazes don’t get out of control. Negative impacts, such as smoke and other disruption on communities, were among the trade-offs residents in bushfire-prone areas had to take, he said.