Australia — MANAGEMENT to lessen the severity of bushfires must be guided by community values, Bushfire CRC research director Richard Thornton says. That makes things complicated.
Prescribed burning ahead of bushfire season is the surest way to limit the prospect of a hazardous fire – although it can’t prevent them – but every prescribed burn is different, depending on what its objective is.
For instance, burning off ground litter demands a different sort of burn, and different weather conditions, than one designed to reduce the fire-carrying bark in some forests.
It all comes under the broad heading of “land management”, Dr Thornton said, and how we want land to be managed varies from place to place.
Much of Australia’s bushland has evolved around regular low-level burning by Aboriginal people. With colonisation by fire-phobic Europeans, the continent’s fire regime changed from frequent but small fires to infrequent and large fires.
After a succession of devastating bushfires in the past decade, and the promise of more to come in a warming climate, the pressure to develop a widespread system of pre-colonisation mosaic burning for land management is growing.
Prescribed burning isn’t a guarantee that catastrophic bushfires won’t occur, Dr Thornton said.
In certain weather, any fire is going to be a bad fire, and some fires will always be impossible to control.
During Victoria’s Black Saturday bushfires, fire was spotting 30-40km ahead of the main fire front, a prospect that can’t be managed for.
The challenge for prescribed fire policy is that 21st Century Australia has a very different relationship with nature than the people who managed the country for the past 50,000 years.
The potential for a bushfire to cause property loss is highest in peri-urban areas, but these are also where the greatest friction occurs between fire services and property owners who don’t want their environment blackened and their homes to smell of smoke.
Too many prescribed burns can reduce biodiversity – as can too few in some places. Burning for an ecological outcome requires different conditions and management than burning purely for hazard reduction.
Australia today also more ways of lighting accidental fires compared to those available in the days before settlement.
Work by Bushfire CRC researchers found that just six per cent of bushfires are lit by natural sources, like lightning. The rest are lit by human activity – possibly half lit deliberately, either by arson or misguided burning-off, and most of the remainder by accident, through sources like cigarette butts, slashers and chainsaws.
Education might help cut back some of these ignition sources, Dr Thornton said, but unexpected ignition will always happen.
Most of the major Black Saturday fires were lit by power lines brought down by gusty winds and trees. Of the two that were arson lit, one was started by a pair of teenagers too mentally impaired too prosecute.