Traditional fire management strategies such as hazard reduction burns, logging, and the thinning of undergrowth have increased the flammability of forests, new research has found.
Key points:
- The lead author of the report says fire management techniques need to be reconsidered
- The researchers say interfering with nature is increasing the risk of severe fires
- The RFS says the report does not offer practical advice
A report entitled "Identifying and managing disturbance-stimulated flammability in woody ecosystems" has revealed that logging or prescribed burning can prevent a forest maturing and becoming less flammable.
The report, published in scientific journal Biological Reviews, draws on studies of the severe bushfires in 2009 and 2019-2020 to identify factors that may increase the intensity of a burn.
Lead researcher David Lindenmayer, a forestry and environmental management expert from Australian National University, said the findings questioned the effectiveness of traditional fire management strategies.
"This is quite confronting," he said.
"We need to start thinking differently about what's happening in our forests."
'Pulse in flammability'
The report found that as trees grew taller the risk of extreme blazes decreased.
"The chances of flames jumping from the understorey to the over storey — to create very dangerous crown fire conditions — is reduced," Professor Lindenmayer said.
"The forest transitions to something that's cooler, wetter, less fire-prone and less susceptible to very high severity fire."
Professor Lindenmayer said the management techniques that were in place disrupted forests from maturing.
"Our history of forest management, including past logging and past thinning, has actually added to the fire burn," he said.
"Prescribed burning will reduce fuel loads for a few years, and then, as the forest regenerates after having been disturbed, you get this pulse in flammability."
Professor Lindenmayer said periodic hazard reduction burns could leave a forest in a higher state of flammability indefinitely.
"The risks associated with increasing the flammability of the forest are real, as we've seen," he said.
"We need to think about how a nature-based approach can shift forests back towards being less flammable than they are now."
The report recommended hazard reduction burning, if used at all, should be done close to housing and carried out frequently, before the spike in forest flammability.
"The jury's out on how effective that might be," Professor Lindenmayer said.
RFS disputes findings
RFS community risk director Simon Heemstra said while the report offered some insights regarding fuel accumulation it did not outline anything the organisation could put into practice.
"To wholesale adopt the recommendations of this report would make the landscape much more dangerous and threaten life and property," he said.
Dr Heemstra said prescribed burns reduced the fuel load, helped certain vegetation reproduce, made putting out small fires easier, and provided training for RFS staff.
"There is always a reduction in risk when you reduce part of the fuel," he said.
"Fires are going to be not as intense, not run as fast, and be more easily controlled.
"Our losses of property and risk to human life are significantly reduced once we reduce fuel load.
"The more we implement prescribed burning and have strategies to try to reduce ignitions and suppress fires, the more we're reducing these big fires with a very significant impact."
Dr Heemstra said the report was overly simplistic in its suggestions about lightning strike modelling and drones dropping retardants on ignitions to prevent sparks becoming bushfire blazes.
"There are options we need to look at in the future, but it's not a silver bullet and it needs to go in the mix with everything else we are doing as far as bushfire risk management," he said.
Dr Heemstra said the RFS aimed to burn bushland every five to 10 years to minimise risk.
He said that was an ancient practice.
"The Australian landscape was shaped after tens of thousands of years of management through Aboriginal Australians and their cultural burning practices," he said.
"There is a lot to be learned and understood from the use of fire in the landscape."