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Does fuel reduction burning help prevent damage from fires?

There has been an outcry in Tasmania against legal restrictions on fuel reduction. AAP Image/Twitter Botonaine

As the fires that started in Tasmania in early January continue to burn, a rising flow of letters to the editor, radio raves and internet utterances are questioning whether the state and local governments in Tasmania have done enough to reduce fuel in the forest.

People urge lifting legal restrictions on fuel reduction related to threatened species and vegetation conservation. They want money spent on nature conservation programs, like fox control, be diverted to control burning the bush. They blame the Greens for everything. Some hark back to the days when hardy, practical Tasmanians were able to burn the bush at will in their traditional ways.

What is our scientific knowledge of these issues? Are the Tasmanian governments managing the bushfire risk appropriately?

February 7 1967 was a day of comparable severity to January 4 2013. Both days hovered between extreme and catastrophic on the current fire danger scale. Most of southeastern Tasmania burned on February 7, more than 100 human lives were lost and thousands of buildings were reduced to corrugated iron leaning on a brick chimney. On January 4 2013, no lives appear to have been lost, the fires have covered only a small part of the southeast and about 170 buildings have been incinerated.

The major reason for this spectacular difference in outcomes is the small number of fires that were alight or were ignited on January 4 2013, compared to the extremely large number on 7 February 1967. Back then, the response of some people to a bad fire day was to light up surrounding bush to protect their properties.

In 1967 fire was seen as a tool for use by everyone on the land. For instance, fire was widely used to eliminate unpalatable growth on grazing properties. Today, most graziers do not use fire, because of the legal and social difficulties associated with ignition. The lack of fire on these grazing properties has caused a thickening of the tree layer and higher levels of fuel on the ground. In some places, short grasslands that do not readily burn have been replaced by highly flammable shrubs. Many nature conservation values have suffered a decline.

In 2013 most of the Tasmanian population has been convinced by weight of argument, experience and legal coercion that burning the bush is too risky an activity not to be left to professionals. This change in social attitudes has resulted in a dramatic drop in fire frequency in dry eucalypt forests, the ones most likely to burn.

The main reason for the lack of human mortality on January 4 2013, compared to other catastrophic fire days, is the emergency response activity of state government agencies. They have developed integrated emergency response plans that involve all government and volunteer organisations, and have deluged the local populace with information on how to prepare for fires and what to do when a fire occurs.

Fuel levels in the bush are very much a minor issue in mitigating property damage and human mortality from vegetation fires. An analysis of property loss in the catastrophic 2009 Victorian bushfires showed that there was no difference between being adjacent to state forest and being adjacent to a national park, despite the higher level of fuel control in the former.

The best predictor of loss was the vegetation within the vicinity of the house. Having no woody growth (presumably a surrogate for no ground fuel) meant a better chance of having a house after a fire.

It has become abundantly clear that fire protection of property relates largely to what happens immediately around a property and the minimisation of opportunities for spark ingress to the buildings themselves. There is also a substantial random component in property survival that motivates fleeing in extreme and catastrophic conditions. In extreme and catastrophic fire weather, the front burns through or leaps fire breaks, apparently bare paddocks, salt water inlets, rivers and any other obstacles to its progress, with spot fires up to 20km ahead of the main set of flames.

In less than extreme fire weather, areas of fuel-reduced bush will act as safe places for back burning and may act as barriers to spread. However, if nothing else is done, large areas need to be planned burned to lower the probabilities of losing fire-susceptible assets.

Karen King and her associates modelled the areas that needed to be burned in western Tasmania to reduce losses of fire-susceptible rainforest and alpine vegetation. Burning less than 10% of the area of buttongrass moorlands per year had virtually no effect.

In southeastern Tasmania and elsewhere, it is not possible to safely control burn the widespread wet eucalypt forests. On extreme and catastrophic fire days, fires will burn through recently fuel-reduced dry forests and apparently bare paddocks to burn explosively in these wet forests.

Tasmanian government agencies responsible for fire management are well aware of the above realities. They see fuel reduction as desirable in some situations, while being only a small part of the process of preventing and mitigating fire disasters. In both planning and implementing fuel management and fighting fires, the Parks and Wildlife Service, Forestry Tasmania and the Tasmanian Fire Service work well together to achieve the outcomes they can within the budgets they are given.

In response to the fire at Scamander in northeastern Tasmania in 2007 and the inquiry into the Victorian 2009 fires, the Green ministers convinced the Tasmanian State Government to increase funding for planned burning. This not only has the minor importance in fire disaster prevention described above, but is also useful for maintaining timber values by preventing crown fires, and for maintaining populations of the many native species that suffer from a lack of fire regimes suited to their life cycles.

We need much more planned burning for ecological purposes. We probably do not need much more for fire disaster prevention and mitigation. However, burning the bush after fire disasters has been a time-honoured way for Australians to cope emotionally with their powerlessness in the face of extreme natural events, so we are highly likely to see more of it.

Perhaps it can be done where it is needed for nature conservation. The letter writers and tweeters are unlikely to notice.

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