'Not if, when': Former NSW Fire Chief Greg Mullins' 'Black Summer' warning

Wildfires in Australia burn within sight of the suburban fringe of the city of Canberra on January 31, 2020. Photo / Getty Images

La Nina's heavy rains have dampened summer plans for people on Australia's east coast, but that may not be its worst effect, with the weather system likely to increase the severity of future bushfires.

In an opinion piece for The Age, former New South Wales Commissioner of Fire and Rescue Greg Mullins warned increased rain would lead to "prolific grass growth" in otherwise desert landscapes. Once dried, this becomes fuel for grass fires, which when combined with wind, can cause sparks to reach woodland areas with devastating affects.

Issuing the bleak warning, the renowned firefighter said this scenario wasn't a question of if, but when.

"It is inevitable, as they do after every La Nina, that the new grasslands will eventually wither and die. They will then probably burn," he wrote.

"It will only take a flash-drought, a heatwave, an intense change of weather and the growth that has sprung up could turn into ominously heavy fuel loads for fires."

Mullins used the example of the catastrophic 1974-75 bushfire season which occurred after rains caused unprecedented grass growth. The resulting fires resulted in the deaths of six people and saw around 15 per cent of Australia's land mass suffering "extensive fire damage.

"When those grasslands inevitably turned brown and died, they burned," he wrote. "In 1975 over 117 million hectares burned across every state and territory except Tasmania, and Australia's centre turned red again. Fires burned for months."

Central Australia most at risk

A similar warning has come from the Commonwealth Scientific and Industrial Research Organisation (CSIRO). Research from the science body found that Central Australia is likely to experience far greater levels of burning after high rainfall.

"Across Central Australia, the system is much more driven by rainfall for most of the time – if there's sufficient fuel there, the conditions would support a fire," said CSIRO rangeland ecologist Garry Cook, speaking to the NT News.

"That water is going to go down the rivers, into big flood out areas, down the Finke, and across all the country running off the MacDonnell Ranges, producing a lot of grass growth.

"By the following spring and summer, hot, dry weather, some lightning storms or something like that happens, and the system gets put alight."

A similar situation was seen in 2011 to 2012 where months of damaging fires swept through the Northern Territory and Western Australia. This followed the area's wettest dry season in 2011.

Firefighters at a wildfire northeast of Perth in February 2021. Photo / AP

Emergency bushfire warnings issued for Perth, WA's southwest

Despite predictions for grave bushfires, areas in Perth's east and WA's southwest continue to be ravaged by flames.

The Department of Fire and Emergency Services said it was too late for residents of Warrigal Estate in the Perth Hills to leave, with firefighters battling to contain blazes. As of 10.25pm on December 26, the DFES said there was a clear "threat to lives and homes".

"It's too late to leave, leaving now would be deadly," they advised.

"You need to shelter in your home in a room away from the fire front and make sure you can easily escape.

"You must shelter before the fire arrives, as the extreme heat will kill you well before the flames reach you."

Residents in parts of City of Swan, Wooroloo, Chidlow, Gidgegannip and the Shire of Mundaring have been told to "act immediately to survive," with recommendations to leave if safe to do so.

Hot to Very Hot throughout today with forecast temps up to 49C in the Northwest. Interesting Satellite image this morning; low cloud associated with the cool change visible over the Bight, whilst extensive areas of high level smoke from WA bushfires visible in the west. pic.twitter.com/ghnQfoRbPL

— Bureau of Meteorology, South Australia (@BOM_SA) January 2, 2019

Climate change

While fires are an ever-present during an Australian summer, the role of climate change is becoming an increasing factor, a fact that's been supported by a growing body of researching.

A report published in March of 2020 by the World Weather Attribution consortium found that a global temperature rise of 2C would increase the likelihood of hot, dry weather conditions that could lead to bushfires by at least four fold.

Speaking to the BBC, co-author of the study, Professor Geert Jan van Oldenborgh of the Royal Netherlands Meteorological Institute warned that the 2020 bushfires showed the limit of Australia's firefighting capabilities, with fears larger fires could overwhelm the system.

"(In 2020) the fire prevention system in Australia, which is extremely well prepared for bushfires, was straining. It was at the limits of what it could handle, with volunteers working for weeks on end," he said.

"As the world warms, these events will become more likely and more common. And it's not something that we are ready for."