Climate change driving Aus bushfire activity: CSIRO

Climate change has driven a significant increase in Australia’s bushfire activity over the last three decades, according to new research conducted by CSIRO and published in the journal Nature Communications. 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.

Claimed to be the first of its kind, the CSIRO research combines analysis of previous bushfire sites with eight drivers of fire activity including climate, fuel accumulation, ignition and management (prescribed burning). Over 30 years of satellite data and 90 years of ground-based datasets from climate and weather observations, and simulated fuel loads for Australian forests, formed the basis of the research, which allowed researchers to identify climate change-driven increases versus natural variability.

“While all eight drivers of fire activity played varying roles in influencing forest fires, climate was the overwhelming factor driving fire activity,” said CSIRO scientist Dr Pep Canadell.

“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 megafire years occurred after the year 2000; a megafire year is defined as the cumulative burned area of forest over one year of more than 1 million hectares. Australia’s mean temperature has meanwhile increased by 1.4°C since 1910, with a rapid increase in extreme heat events, while rainfall has declined in the southern and eastern regions of the continent. And while global fire activity is decreasing, 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%, and 800% 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 10-fold increase.

“In Australia, fire frequency has increased rapidly in some areas and there are now regions in the south-east and south with fire intervals shorter than 20 years,” Dr Canadell said. “This is significant because it means some types of vegetation won’t reach maturity and this could put ecosystems at risk.

“Understanding these trends will help to inform emergency management, health, infrastructure, natural resource management and conservation.”

Image caption: The North Black range fire west of Braidwood, east of Canberra. Image credit: CSIRO.

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