Bushfires are bound to recur and wreak even more devastation unless we undertake pre-emptive fuel-reduction burn-offs, writes Peter Westmore.The tragic loss of four lives and the destruction of 500 houses in the January 2003 bushfires in and around Canberra were the subject of a Coroner's inquest concluded last December.Most media reports focused on the actions of the ACT Government and Emergency Services Bureau and Bushfire Service in handling the fire emergency.
But Chapter Four of the coronial inquiry examined the state of the forests around the ACT at the time of the bushfires, and made recommendations for the future which have relevance throughout Australia.
The Coronial inquiry heard that there had been numerous bushfires in or near the ACT since 1920, perhaps the most serious of which were in 1939 and 2001, shortly before the latest disaster.
Reduced impactThe report quoted a paper by CSIRO bushfire scientist, Phil Cheney, which stated:
"Since settlement, basic fuel reduction in both forest and pastoral lands has reduced the impact of bushfires. There are few official records of deliberate burning-off, but oral histories suggest that burning-off in the Cotter catchment was extensive between 1926 and 1945 and low-intensity fires in the spring of 1938 reduced the impact of the 1939 fires, and crash-grazing (grazing pastures until they are eaten out) was common around homesteads on the rural leases until the 1970s."
It added that broad-area burning was conducted in the bushfire areas during the late sixties and seventies, "but after 1985 an active hazard-reduction burning program has not been pursued".
In the mid-1990s, following serious fires in New South Wales, an inquiry was held by Mr H.R. McBeth into the then ACT Parks and Conservation Service, and into the activities undertaken by the service to modify the impact of bushfires in the ACT.
After reviewing the history of bushfires in the ACT, the McBeth inquiry stressed: "If the existing government statutes, departmental structures, reporting relationships and programming of wildfire-mitigation works continue as currently structured, it is inevitable that significant loss of assets will accrue together with loss of life during the next single, multiple or configuration fire event.
"The urban-rural interface will obviously bear the brunt of such losses.
"The author stresses a set of climatic conditions will eventually produce 'fire weather' conditions of such an intensity that such losses will occur. It is not if such a disaster will occur, but when."
He concluded that the only way of mitigating the effects of such a fire would be to reduce forest fuel loads.
In 2002, the year before the Canberra fire, Emergency Services Bureau planning officer Rick McRae pointed out that "Namadgi National Park covers a large fraction of the ACT, and is the area in which extensive landscape fires are most likely to occur …. For most of the twentieth century, the area suffered very large wildfires every decade on average. The legacy of these was that its fire-age distribution was concentrated in a few large clusters. However, there has been no large fire in 20 years now, and basically the entire area is now at or near equilibrium — i.e., maximum fuel loads. Only around 20 ha out of 120,000 would be fuel reduced in any way."
Mr McRae recommended a broad area fuel-reduction program involving prescribed burning of areas of the national park in rotation, to achieve a "fire age spectrum" where roughly 20 per cent of the park was burned in the previous 10 years, a further 20 per cent in the previous decade, and so on.
The CSIRO fire expert, Mr Cheney, gave evidence to the inquest that "hazard-reduction burning will reduce the total load of fine fuel and is also effective in reducing the height and flammability of elevated fine fuel such as shrubs and suspended dead material. Burning is the only practical way of reducing the fibrous bark on trees which is the prime source of firebrands that cause spotting [i.e. spot fires ahead of the main fire front]".
Mr Cheney also said that if a bushfire is sustained by 20 tonnes of combustible fuel per hectare, it can only be suppressed in conditions of low fire danger. He confirmed that the WA Department of Conservation and Land Management (CALM) was the only organisation in Australia to have undertaken prescribed burn-offs.
"In my opinion," he said, "they are certainly the most advanced in using prescribed fire and fire management generally."
He also said that CSIRO research had shown that litter on the floor of eucalypt forests built up relatively rapidly after a fire, so that within five to eight years, you have accumulated sufficient fuels" to sustain bushfires, "and that it requires re-treatment to reduce the fire behaviour to a manageable level".
Unless this lesson is learned, the wildfires which engulfed the suburb of Duffy in Canberra, and which burned in Alpine areas of Victoria in January 2007, will recur every year in different parts of Australia.
— Peter Westmore.
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