Fuel reduction (also called controlled burning) is a key tool used by land managers to reduce the intensity of fires when they do occur. Its a simple theory: do a controlled, ‘cool’ burn through an area to reduce the amount of fuel on the forest floor.
In Victoria, there is an annual target, whereby public authorities need to try and burn 5% of public land each year. This has lead to widespread criticism that Parks are burning areas a long way from ‘assets’ (house, farms, etc). In effect, it seems that the target has become political rather than about reducing fire risk. There is also evidence that some fire regimes being imposed on some landscapes may be causing ecological harm or even potentially increasing fuel loads through changing vegetation structure.
As noted by the Victorian National Parks Association, “The Victorian Bushfires Royal Commission’s recommendation to burn 5% of Victoria’s public land each year for fuel reduction was not actually recommended by its own expert committee. That group of fire scientists and ecologists almost universally recommended burning 5% of the ‘foothill forests’ (largely our stringybark forests), and that the burning should be monitored as an experiment”. So we have a land management tool being applied across the state, including in areas where there is no evidence that it will reduce fire risk.
The 5% statewide target has been strongly criticised in three consecutive reports by the Commission’s own implementation monitor, and the recent investigation of the target by Victoria’s Inspector General of Emergency Services has recommended it be replaced by strategic fuel reduction objectives.
It is now being reported in the media that new research published in the Journal of Biogeography is suggesting that controlled burning is not effective at reducing fire risk in many parts of the ACT, NSW, Victoria and South Australia.
The research, published in a report called Biogeographical variation in the potential effectiveness of prescribed fire in south-eastern Australia looked at the impacts of fuel reduction practises in 30 bioregions across south eastern Australia. It found that there were only four regions where prescribed burning made a difference to the intensity of later fires. Each of these were notable for its forested areas, relatively high rainfall, high fire activity and mild climate.
The report found that:
Leverage (ie reduction in fire intensity as a result of controlled burning) was inferred in four bioregions while in the other 26 bioregions no leverage was detected or prescribed fire had the opposite effect (fire-follows-fire). Leverage occurred in the forested eastern section of the study area, where rainfall, fuel load and fire activity is high and fire weather is mild. In all bioregions, weather was a stronger predictor than past-fire extent of area burnt in a particular year.
As you would expect, the research highlights the fact that different types of vegetation respond to fire in different ways:
Our analysis of leverage shows that the effectiveness of prescribed fire varies regionally in predictable ways, which means that fuel management strategies applied in one region are not necessarily applicable in another. In most bioregions prescribed burning is likely to have very little effect on 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.
This is significant because there is a tendency to ‘one size fits all’ approaches in how public land managers do their burns. Because of the political imperative to reach the 5% target and the economy of scale that comes with putting staff and resources into the field, many of our burns tend to be large (greater than 100 hectares) rather than the ‘mosaic’ effect that had previously been created by traditional indigenous land use, which used many small fires across the landscape.
This report highlights yet again the fact that the current burning model is a very blunt instrument which is being used in an environment where we need a much more site appropriate and nuanced manner.
The report is not available for free, but details on purchasing the report can be found here.
There is an article from the Sydney Morning Herald available here.