Megafires that burn more than a million hectares increasing due to climate change, CSIRO finds.

 Extract from ABC News

By national regional affairs reporter Jess Davis

Posted 10 hours ago

The CSIRO has collected data from the past 90 years to track the increasing frequency of megafires.(ABC News: Brendan Esposito)

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Climate change is increasing the frequency of megafires in Australia and putting entire ecosystems at risk, new research by the CSIRO has found.

Key points:

• The frequency of megafires, in which over 1 million hectares of forests were burnt, increased suddenly after 2000
• The worst fire seasons typically follow a La Niña weather phenomenon, which Australia is currently experiencing
• The amount of prescribed burning has not changed over the past three decades

Over the past three decades, Australian forests have undergone an 800 per cent increase in the extent of the area burnt bushfires, with researchers warning ecosystems are at risk because they are not able to recover between devastating infernos.

The research, published in the journal Nature Communications, is based on a first-of-its-kind study that used 32 years of satellite data and 90 years of ground-based datasets from climate and weather observations.

The increase in burnt areas has not been limited to the summer months. Since 1988, the fire season has extended into the cooler months, with a more than fivefold increase in the annual mean burnt area in winter and a threefold increase in autumn.

"All these things have completely changed over the last 15 years, where fundamentally fire has spread throughout the entire 12 months," CSIRO chief research scientist Dr Pep Canadell said.

"If we look at just the burn area during the cold season, we don't see a linear increase, we actually see an exponential increase of burn area of this period."

 

The health impacts of megafires, including from bushfire smoke, can be significant.(ABC News: Jonathan Hair)

Dr Canadell said the study combined analysis of previous forest fire sites with eight drivers of fire activity, including climate, fuel accumulation, ignition and prescribed burning.  

"While all eight drivers of fire activity played varying roles in influencing forest fires, climate was the overwhelming factor driving fire activity," he said.

"The results also suggest the frequency of forest megafires are likely to continue under future projected climate change." 

Hazard reduction not a factor

Since the Black Summer bushfires, there has been fierce debate over the role hazard reduction burns played in the severity of the fires, but Dr Canadell says prescribed burning has not actually changed.

"Overall, prescribed burning really hasn't changed at all and, perhaps most importantly, just to realise that we are burning one per cent per year of the forests, which is a really a small amount," he said.

"I think it's very difficult to imagine that fuel loads would be an important component in driving what we've seen — it's really climate and weather."

 

Over the past 30 years, Australian forests have seen an 800 per cent increase in burnt areas.(ABC News: Mridula Amin )

CSIRO scientist Mick Meyer agreed and said prescribed burning was mostly done to protect assets.

"If you tried to burn the whole of the country, you'd be changing the ecosystems in effect," he said.

"Once the fire weather gets really severe, above a fairly low threshold in fact, the fires just take off and they exceed the capacity of the agencies to suppress them."

Don't be fooled by La Niña

Dr Canadell also warns that despite a reprieve with wet conditions this year due to a La Niña, the year following such a weather phenomenon typically brings a bad fire season.

"The highest area of burn actually comes right after a La Niña year, because the wetness across the continent really brings up the fuel loads," he said.

"We expect that most likely next year, unless there was another La Niña, which is highly unlikely, it will be a very important and large fire season across Australia."

 

The Black Summer bushfires left widespread carnage across the east coast of Australia.(ABC News: Mridula Amin )