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How often and where prescribed burning takes place needs a rethink if Australia's plants and animals are to be preserved, according to a study of biodiversity loss due to the Black Summer fires.
Some 3 billion vertebrate animals were estimated to die or be displaced by fires on the east coast alone.
But the severity of these losses depended largely on past fire history within the 10.3 million hectares that burnt, according to a new study published in the journal Nature.
The study analysed 62 datasets compiled from several universities and government departments containing 810,000 records of 2,200 plant and animal species in New South Wales, Victoria, Queensland, South Australia and Western Australia.
The researchers quantified the impact on biodiversity in the burnt areas following the Black Summer fires.
Ecosystems that had three or more fires in the 40 years leading into the 2019–20 fire season had negative impacts on biodiversity 87–93 per cent larger than areas that had only burnt once or not all in the same period.
Sites that had burnt within less than 10 years of Black Summer also had 70 per cent higher negative impacts on species than areas that had not been burned for 20 years.
Six ecosystems were covered, including alpine, wetland, rainforests and dry and wet eucalypt forest.
While overall Black Summer had a 55 per cent negative impact on the amount of different species, 44 per cent was positive.
Study lead author Don Driscoll, a terrestrial ecologist from Deakin University, said some groups of animals such as mammals saw especially severe declines.
"A lot of species are vulnerable to effects of fire, which we are really concerned about, but the increases from a conservation perspective don't balance that ledger,"he said.
"Also there are increases with feral predators, which are more effective hunters in those [burnt] habitats.
"The dilemma is our study shows sites frequently burnt before fire get much bigger declines caused by the fire."
Murdoch University disturbance ecologist Joe Fontaine, who was not involved in the study, said the evidence was clear that nature's responses to fire become more extreme with past disturbances, such as prescribed burning.
"More fires in recent years, higher levels of drought impact, and less protected area were all associated with greater destabilisation," he said.
"This greater variance is cause for concern and is one indicator and pathway of ecosystem collapse. It has been documented in other contexts, such as coral bleaching of the Great Barrier Reef."
Dr Fontaine said the new study suggested a greater need to consider biodiversity risk when planning prescribed burns, but should also be validated in areas other than eastern Australia.
How much fire should we have?
The study suggested that intermediate fire intervals, between 11 and 20 years, created the least disruption for biodiversity. Long intervals between burns were also needed to provide species' refuges.
Professor Driscoll said having unburnt areas around a site that been burnt also limited the negative biodiversity impacts of a fire.
He also noted the study found slightly fewer negative impacts to biodiversity within nature reserves and national parks, but not state forests that still included recreational and logging uses.
The findings clash with current practices for reducing bushfire risk to people and property, which vary across the country but include smaller six- and eight-year intervals.
Professor Driscoll said he thought there were implications for fire management out of the study.
"We could reduce the impact of these megafires by breaking them up, by trying to create unburnt patches.
"Current management is to use frequent fuel reduction burning to limit the effect of large fires.
"What we do by frequently burning forests is set them up for a big fall with the next fire."
Loading...As an alternative to frequent prescribed burns, other than for protection of lives and property, Professor Driscoll said fire management agencies in government should invest more urgently in rapid fire suppression.
This would include investing more resources into quickly detecting and extinguishing fires before they grow too large.
Professor Driscoll said he thought there were signs agencies were embracing changes in how they managed risk to biodiversity with intense fires predicted to become more common due to climate change.
"[There's] the famous example of efforts going into Wollemi pine, so putting in sprinkler systems and deliberately putting out fires when it comes into those ecosystems," he said.
What do fire managers think?
An Australian Capital Territory government spokesperson said the study provided significant data that were valid for consideration in fire management planning for the territory.
The spokesperson said the government recognised the threat of megafires and was considering ongoing research around biodiversity as it developed its new strategic bushfire management plan.
"Over past years, the ACT government has invested in strengthening ecological and biodiversity considerations in fire management activities, including fire preparation, prevention and suppression operations.
"Protecting biodiversity during bushfires is a key priority and is best performed in an integrated manner alongside the priority of protecting life and property."
A WA Department of Biodiversity Conservation and Attractions spokesperson said prescribed burning was its state's primary mitigation measure.
"From a biodiversity perspective, prescribed burning is undertaken to maintain a range of wildlife habitat types.
"Prescribed burns occur in more favourable conditions than intense summer bushfires, enabling animals more opportunities to safely move into areas of unburnt vegetation and various plant species opportunities to regenerate."
The spokesperson said WA already had an aerial spotter fleet for the fire season and kept an eye on new detection technologies.
"This complements the proactive approach of prescribed burning and strategic fuel management zones that seeks to manage and reduce fuel loads across the landscape."
A NSW Department of Climate Change, Energy, the Environment and Water spokesperson said it was already responding to some of the key findings in the paper.
"The paper also recommends using Aboriginal knowledge on fire," they said.
"Combining the tolerable fire interval guidelines with Aboriginal cultural knowledge and bushfire management expertise will be an area of growth, in order to help our fire planning agencies respond to a changing climate."
The SA and Victorian governments were also contacted for comment.
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