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New research links Australia’s forest fires to climate change
New research by CSIRO, Australia’s national science agency, shows climate change has driven a significant increase in Australia’s forest fire activity over the last three decades.
A lengthening of the fire season towards Autumn and Winter were also identified, along with an increase in fire activity in cooler and warmer regions including alpine forests in Tasmania and tropical rainforests in Queensland.
The research published in Nature Communications is the first of its kind and combines analysis of previous forest fire sites with eight drivers of fire activity including climate, fuel accumulation, ignition and management (prescribed burning).
The findings were based on thiry-two years of satellite data and 90 years of ground-based datasets from climate and weather observations, and simulated fuel loads for Australian forests. This allowed researchers to identify increases driven by climate change from natural variability.
CSIRO scientist, Dr Pep Canadell, said the research was one of the most extensive studies of its kind performed to date, and was important for understanding how continued changes to the climate might impact future fire activity.
“While all eight drivers of fire-activity played varying roles in influencing forest fires, climate was the overwhelming factor driving fire-activity,” Dr Canadell said.
“The results also suggest the frequency of forest megafires are likely to continue under future projected climate change.”
Over the last 90 years, three of the four mega fire years occurred after the year 2000. A mega fire year is defined as the cumulative burned area of forest over one year of more than 1 million hectares.
Australia's mean temperature has increased by 1.4 degrees Celsius since 1910, with a rapid increase in extreme heat events, while rainfall has declined in the southern and eastern regions of the continent. Globally fire activity is decreasing, however, the extent of forest fires in Australia is increasing.
When comparing the first half (1988 – 2001) with the second half (2002-2018) of the record studied, the research showed that the average annual forest burned area in Australia increased 350 per cent, and 800 per cent when including 2019. Comparing the same time period, the research showed a five-fold increase in annual average burned area in winter and a three-fold increase in Autumn, with Spring and Summer seeing a ten-fold increase.
“In Australia, fire frequency has increased rapidly in some areas and there are now regions in the southeast and south with fire intervals shorter than 20 years. This is significant because it means some types of vegetation won't reach maturity and this could put ecosystems at risk,” Dr Canadell said
“Understanding these trends will help to inform emergency management, health, infrastructure, natural resource management and conservation.”
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Professor John Handmer is Director of the Centre for Risk and Community Safety at RMIT University in Melbourne.
While the paper is the first national view of the subject; it reinforces understanding gained from smaller scale studies that climate and weather are the primary drivers of changes in large intense wildfires in Australia. The paper also highlights the lack of clear evidence for the impact of planned fuel reduction burning with respect to trends in large wildfires. This may have important implications for policy.
Fuel reduction through planned burns plays a critical role in protecting assets, but this is quite different to preventing major wildfires.
As the paper finds, fire frequency is now so high in some areas that local extinctions could be occurring. These fire frequencies are a mix of wildfires, which the paper examines, and planned burns, which sometimes appear to increase ecosystem stress by burning previously unburnt remnants and (plant and animal) refuges.
Professor Jason Sharples is a Professor of Bushfire Science at UNSW Canberra
This study links increases in burnt area over Australia to concomitant increases in dangerous fire weather and conditions conducive to violent pyroconvection associated with anthropogenic climate change. As such, it adds to the growing body of scientific evidence demonstrating the effect that climate change is having, and will continue to have, on global fire regimes – especially in regions such as southeastern Australia and the western United States. Warmer global temperatures directly increase the prevalence of fuels with dangerously low moisture content (associated with profuse spotting) and indirectly influence weather patterns leading to drought and critical fire weather such as heatwaves and dangerous frontal systems. Of concern is the fact that the study found no clear influence of fuel load, which is one of the few factors influencing fire behaviour that we have the ability to control. This suggests that bushfire risk reduction measures such as prescribed burning may be of only limited effectiveness in the absence of broader action to mitigate climate change.
Professor Bob Hill is Director of the Environment Institute at the University of Adelaide.
On the potential risks of local ecosystem collapse:
This is an important area of research and is a clear priority to understand, but it is complex, because it infers no seed trees at all survive in a region under investigation so that there is no seed source. It is often, if not always, more complex than that, with some vegetation patches surviving the fire in a region and hence being available as a post-fire seed source. Nevertheless, this is an obvious potential source of local extinction and one that will be exacerbated by climate change. This should be an important focus for those charged with vegetation management and especially controlled burning, to help to ensure that such species are given the best possible chance of surviving into the long term. In the worst case, we need backup plans for what the replacement vegetation in regions where this may occur might look like, because with worsening conditions such losses may be inevitable.
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