A body of research is challenging long-held beliefs that lessening fuel load inherently lowers fire risk.
Studies published by researchers from the Australian National University and Curtin University since 2022 have claimed long-held research that underpinned the Western Australia Department of Biodiversity, Conservation and Attractions’ burning regime is incorrect.
Their study published in August of that year replicated the department’s underpinning research from 2009 and determined prescribed burns had negligible effects on bushfire area. Another study published in March of 2022 found that forests in southwest Australia are at their highest fire risk during the tens of years of regrowth after a fire, but continuously decrease in fire risk once reaching their mature period.
A new study, just published by the researcher Philip Zylstra, an Adjunct Associate Professor at Curtin University, and David Lindenmayer, a Distinguished Professor at the Australian National University, delved further into this dichotomy and examined whether a full phase-out of prescribed burning would decrease severe bushfires and help forests return to their original, pre-frequent disturbance states.
The researchers said their study shows long-unburnt forests limit fire without human intervention, even as the climate changes. They found that 77% of all areas burned in over 500,000 hectares (1,235,527 acres) of forested national parks in southwest AU were due to prescribed burns, with 20% burned from escaped prescribed burns and 23% from backburning.
“If large-scale prescribed burning and incentives to backburn ended, the area burned annually would immediately fall 87%, leaving only fires started by lightning, accident or arson,” the researchers wrote this month in an article for The Conservation. “Our modelling suggests less area would be burned in the hotter, drier climate of 2100 than it is today if both widespread burning policies were ended.”
“Humans have a deep-seated desire to intervene in nature. But our research shows long-unburnt forests act to limit fire without human intervention – even as the climate changes.”
The researchers instead called on authorities to invest in rapid fire detection and attack, better resourcing firefighters, training and employing more specialist remote area firefighters and exploring fire-fighting drones.
They stressed that these latest findings relate only to the forests of south-west Western Australia. However, they quote their own 2023 research to claim that other Australian forests, and Northern Hemisphere forests, may also become more flammable through burning.
A spokesperson from the Western Australia Department of Biodiversity, Conservation and Attractions said that any claims that forest flammability declines with age rest on inadequate data and following them would be unwise.
“[DBCA] research confirms that prescribed burning is effective in reducing the frequency, severity and size of bushfires in south west forests when at least 45 per cent of the landscape has a fuel age of less than six years since last burnt,” the Department statement sent to The Conversation said. “Removing fire from fire-prone ecosystems often leads to high-severity fires, as seen in a range of significant bushfires that have occurred in Australia and overseas.”
The same researchers faced similar pushback from the department after they published their March 2022 study. The researchers say that scientists from the department told them that their own records contained flawed data and suggested ignoring all records for old forests. The researchers said their findings only became stronger after they removed the reportedly flawed data.
Read the researcher’s full article in The Conversation.
8 Comments
I would put more reliance on the version of Australian fire history at the link below, than I would the poorly informed segment of the 1939 Royal Commission so heavily relied on by the authors of the above story.
https://southeasttimberassociation.com/wp-content/uploads/2015/02/Howitt-Influence-of-Settlement-on-the-Eucalyptus-Forests-1890.pdf
So to answer the question posed at the beginning of the story, the answer is no. Properly planned and implemented low intensity burns are not worsening Australian bushfires.
https://southeasttimberassociation.com/wp-content/uploads/2022/02/To-Burn-or-Not-to-Burn-Nov2021.pdf
“Incentives to backburn”? In NSW at least, the term “backburning” refers to the use of a small controlled fire which is used to remove fuel in the path of a going fire. It burns “back” towards the main fire, usually against the prevailing wind. The only incentives are to stop the fire.
I understand that the Federal Government will provide funds to States for back burning – so there is a form of financial incentive for doing a back burning.
This research is deeply flawed. It ignores the 60,000 years of Aboriginal burning. It ignores the fact that the ‘fuel load’ that grows after fire is actually Australia’s unique biodiversity and, without that vegetation, we would lose many species of wildlife. It is flawed because, as an alternative, it proposes rapid detection and response (which already happens, by the way) but it is dangerous, irresponsible and suicidal to put firefighters on the ground in vegetated areas that have not been burnt for 50+ years and where the fuel loads are extreme. And it ignores the fact that aerial firefighting appliances – planes and helicopters – are severely limited when they can operate (not at night, in strong winds or heavy smoke) and they are very inefficient at putting out fires in forested vegetation where the tree tops hold on to most of the water that is dropped.
Broad area prescribed fire may be used for objectives other than hazard reduction, for example habit management.
Focused hazard reduction, by fire or other means, to locations immediately adjacent to assets, i.e. asset protection zones, remains valid.
I will assume the researchers misspoke, or were misquoted, when mentioning “incentives to backburn”. Backburning, as a fire suppression technique, also remains valid.
Evidenced based WA prescribed burning data clearly highlights that increasing prescribed burning reduces the extent of bushfires. Prescribed burning works, but in SE Australia not enough is being done, around 0.6 % of NSW forests per year, just not adequate. If regular mild prescribed burning doesn’t occur, fuel loads build up to horrendous levels, putting communities and firefighters at risk. EPA mapping of NSW forests in a 2021 report clearly highlight the huge extent of old long term fuels across contiguous landscapes, easy to see why long fire runs occurred. And the impacts on ecosystems from intense bushfires were severe and long duration, a drive up to KNP would highlight this. And the dead tree fuel and dense regrowth following the 2003 and 2019/ 20 bushfires is alarming. Large numbers of lightning strikes in dense fuel areas is not a pretty thought. Aircraft retardants and water aren’t that effective in dense fuels and fuel strata, where there is a lot of standing dead timber, on windy days, at night and at other times. More funding needs to be applied to mitigation.
Roger Underwood.
I write as someone who has been involved with bushfire management in WA forests all my adult life, indeed since 1958. I have been a fire lookoutman, a firefighter, a district forester, a researcher, a bushwalker, an Incident Controller, an administrator, and an activist promoting improved bushfire management. Never once in all these years and occupations have I seen a situation in which the fire threat in the forest declines with increasing age since the last fire, as asserted in your article. Moreover, I have seen many, many times where a fierce fire burns out of an area with heavy fuels into an area with light fuels, and it drops down in intensity, making control easier and safer.
Above all, the Zylstra/Lindermeyer theory has one serious flaw: this is to consider ‘area burned’ as the significant metric. The area burned is meaningless compared with fire intensity. Mild trickling fires have only an ephemeral impact, while high intensity fires destroy, and not only do they annihilate the biodiversity, they threaten human lives and assets. To deny that high intensity fires are more likely to occur in heavy, long-unburnt forests than in forests subjected to fuel reduction prescribed burning is to deny reality in favour of fantasy.
Until Zylstra/Lindermeyer come up with an effective way of preventing large, high intensity fires, they will have status only as critics and academic ideologists, not as serious proponents of responsible forest management with any grasp of practical realities in the real bushfire world.
The authors advance the claim that forest structure, particularly live understorey, is the dominant driver of bushfire behaviour. This view remains highly contested within fire science, and for good reason.
Their argument draws heavily on the 2022 Western Australian understorey paper — a study that has already attracted substantial technical criticism. The use of photographs from the jarrah forest to illustrate fire behaviour is also problematic. As any field forester or fire scientist knows, photographs can be highly site-dependent and, on their own, prove very little about fuel dynamics across a landscape.
The central technical problem is that the authors’ framework places dominant weight on live understorey fuels, while giving minimal attention to the dead surface and near-surface fuels that actually generate the overwhelming majority of a fire’s energy.
In forests such as karri, around 90 per cent of fire energy is derived from surface and suspended fuels such as litter, bark, fine twigs, and dead scrub material. Live understorey vegetation generally contributes only about 10 per cent of the total fuel load. Shrubs can briefly extend the flame height as they flash, but they do not control fire intensity. Fire intensity is overwhelmingly determined by the amount of dead fuel available to burn.
A simple thought experiment illustrates this clearly: Remove the surface and near-surface fuels but leave the live understorey, and a bushfire will struggle to spread. Remove the live understorey but keep the surface and near-surface fuels, and the forest will still sustain high-intensity fire.