State government agencies are amplifying bushfire risk in south-western Australia, say scientists, who further say that government efforts to discredit their research have backfired, resulting in newer and even stronger research.
The original paper by a team of researchers from Curtin University, the Australian National University and the University of Western Australia, published in 2022, examined 55 years of WA’s fire history data.
Researchers say prescribed burning is doing more harm than good.Credit: Wade Ranson
Research lead, Curtin University Associate Professor Philip Zylstra, a former remote area firefighter in New South Wales, said their analysis of records kept by the Department of Biodiversity, Conservation and Attractions concluded that prescribed burning makes the bush more flammable.
The research was dismissed a few months later without explanation by then-WA minister for the environment, Stephen Dawson.
In 2023, the department finally provided its reasoning to Zylstra, who used this information to re-analyse the data.
This re-analysis has now been published in the journal Environmental Research Letters and Zylstra said it found the results were actually more compelling once the department’s concerns were accounted for.
“[Department] scientists argued that due to some areas of poor data quality, all records showing decreasing bushfire risk in [long-unburnt] forests should be removed,” he said.
“Why? The data they were concerned about only covered 1.6 per cent of the area. We removed that small area instead, re-ran the analysis, and the better data gave stronger evidence that burning the bush is a bad idea.”
The two camps agree that burning the bush prompts the growth of a dense understory in the short term that increases fire risk.
But the department believes this is temporary and that it is still the best approach to burn at least every six years.
Zylstra’s team says fire risk would drop if the forests were allowed to grow older because forests would “self-thin” as competition among regrowth resulted in less ground cover as individual plants competed for resources.
Zylstra said forests were unlikely to burn for a short period after a fire, hence the perceived effectiveness of the department’s six-year burn cycle. But they were very likely to burn following that period, as the regrowing understorey became taller and denser.
“All arguments are answered and excuses are gone. Management must protect old forests and properly resource rapid suppression rather than burning,” Professor Zylstra said.
Fellow researcher Emeritus Professor Don Bradshaw from UWA said prescribed burning was “a surefire way to keep the forest highly flammable”, and other team member, ANU Distinguished Professor David Lindenmayer, said the current approach gave “short-term gain for long-term pain”.
But a departmental spokesman said the new analysis still lacked appropriate critical evaluation of the data and did not adequately address persisting sampling issues or landscape factors.
“Following their recommendations would be unwise as it would likely lead to substantially increased fire risk and impact for many decades,” he said.
“Policy continues to be informed by the best available science. The department maintains a statewide fire research program building on knowledge gained over more than 60 years.
“Research shows 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 it was last burnt.”
The spokesman said prescribed burning was the state’s principal risk mitigation strategy for protecting the community from the devastating impacts of bushfires.
“Large, high-severity bushfires burning in long-unburnt fuels reinforce the importance of reducing fuel loads,” he said.
“That way, ground crews and aircraft have a greater chance of success to suppress bushfires quickly and safely.”
The department agreed with the researchers that quick detection and direct on-ground suppression efforts were critical in minimising the size and impact of bushfires.
In July 2023, calls for an independent inquiry into Western Australia’s prescribed burning program were rejected by a parliamentary committee despite scientists and conservation groups labelling the practice damaging and outdated.
A state government spokesman said the department’s fire management program aimed to manage bushfire risks to people, assets, and the environment, while ensuring healthy ecosystems and the conservation of biodiversity values.
“As detailed in the state government’s Forest Management Plan 2024-2033, climate change is affecting landscape dryness and fuel availability, and the frequency and intensity of extreme fire weather,” he said.
“This has the potential to cause larger, more frequent, and damaging bushfires.
“Continuing to focus prescribed burning efforts in zones that protect settlements and other assets, combined with other risk mitigation activity, will mitigate bushfire risk to communities.”
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