What made the Black Summer bushfires ‘unprecedented’

Flames towered high above pine plantation trees at the Ellerslie fire in late December during the Dunns Road fire.

When discussing the 2019-20 bushfire season, the word ‘unprecedented’ has been used time and time again to categorise the fire crisis. Australia has certainly seen disastrous bushfires in the past, including the Black Saturday blazes of 2009, Ash Wednesday in 1983 and Black Tuesday in 1967. Although the Black Summer bushfires of 2019-20 were not the deadliest fire event in the country’s history, the NSW bushfire inquiry found that it was unprecedented due to its length, intensity and areas impacted.

The 2019-20 bushfire season ran for eight months, between July 1 2019 and March 31 2020. The last fires were extinguished on March 2, 2020 following 240 consecutive days of burning. 

A report based on the six-month inquiry into the state’s bushfires found that one of the biggest challenges during the fire season was the large number and size of bushfires running simultaneously.

“In a ‘normal’ fire season, fires generally move from north of the State to south through the season. This season, while fires were burning in northern NSW and Queensland, fires also started in the centre of the State and were burning simultaneously,” the report said.

“The south of the State started to experience fires earlier than in a normal season. This meant that resources, which could usually be deployed as fires moved from north to south, were stretched across the State.”

On November 8 2019, an unprecedented 17 fires were at Emergency Warning level. December 2019 was the most active month, with over 2000 bush and grass fires, of which 120 had been active since November, the report said.

The inquiry also found that fires in NSW overlapped with fires in the ACT, Queensland and Victoria, whilst there were also fires burning simultaneously in South Australia and Western Australia, meaning that “resource sharing between jurisdictions was not available to the same extent it would be in a ‘normal’ season.”

The report states that according to ‘best estimates’, the total area of NSW burnt during the 2019-20 bushfires was approximately 5.5 million hectares, or seven per cent of the state’s total land area. 

“The area affected in neighbouring states and territories in the 2019-20 season provides further context: in Victoria 1.5 million hectares were burnt, in the ACT 86,000 hectares, and in Queensland 7.7 million hectares,” the report said.

The inquiry found that the extent of area burnt in NSW during 2019-20 is significantly larger than recorded in previous bushfire seasons in the state.

A 2004 National Inquiry on Bushfire Mitigation and Management identified previous large bushfire seasons in forested regions of NSW, with over 2 million hectares burnt in 1926-27, 1957-58 and 1968-69, and over 1 million hectares burnt in 1979-80.

In more recent years, 1.5 million hectares was burnt in 2002-03, 1.4 million in 2012-13, 800,000 hectares in 1993-94 and 744,000 in 2001-02.

The report says that the size of individual fires was also historically large for south-eastern Australia.

“Individual fires ranged from smaller than 10 hectares through to over 500,000 hectares, and many individual fires were larger than 100,000 hectares,” the report said, adding that when fires that merged together are taken into account, the size is even greater.

One example of this is the mega-blaze formed in January this year, covering large areas of the Snowy Valleys.

On January 6, the Dunns Road fire, covering 130,000 hectares, merged with the Doubtful Gap Trail fire. Four days later on the 10th, it joined into the East Ournie Creek fire, creating a mega-blaze of 600,000 hectares. By the next morning this had merged with the Green Valley fire, now covering around 800,000 hectares.

As part of the inquiry, the NSW Bushfire Risk Management Research Hub sought to understand whether fuel dryness in NSW was unprecedented leading up to and during the Black Summer bushfire season. Their study showed that across fire affected areas of NSW, conditions were either very much drier than average, or the driest on record.

“The study concludes that it is likely the unprecedented fuel dryness across eastern NSW, particularly in December 2019, contributed to the large extent of area burnt in the 2019-20 bush fire season,” the report says. 

“It also supports other observations that the 2019-20 bush fire season started earlier, as 2019 had more days where dead fuel moisture content was in a critically dry state than at any time since 1950.”

The report found that the “broad, landscape-scale dryness” meant that ‘wet barriers’ in the landscape were generally drier too, and that naturally occurring firebreaks (or ‘soft breaks’) such as moist gullies, swamps or south-facing slopes that normally break up the forest landscape were dry because of severe drought. This, in turn, “greatly increased the probability of ‘mega forest fire events’.”

“The Inquiry’s discussions with fire authorities confirmed this on the ground. Areas that would have usually been used to ‘pull up’ a fire because they were wetter, for example a water course or moist gully, were dry and couldn’t be used as a containment option as they usually would have been,” the report reads.

The study also found that predicted litter moisture content, or dead fuel moisture content, across temperature broadleaf forests was “at record low levels and the total area exceeding critical flammability thresholds was larger and more prolonged than at any time in the last 30 years.”

Of the extreme fire behaviour observed during 2019-20, some notable differences this fire season include the ‘unprecedented’ number of fire-generated thunderstorms, and the amount of biome in eastern Australia’s temperate broadleaf forests were burnt.

“…major fires in eastern Australia’s temperate broadleaf forests – dominated by eucalypts – are relatively common. However, usually only a small percentage of this forest biome burns annually, typically less than 2 per cent, even in more extreme fire seasons,” the report says.

In 2019-20, it is said that almost 20 per cent of this biome was burnt.

The report says that while it is important to examine what did burn, it is equally as important to look at what didn’t burn.

“Notably, the large fires didn’t directly have an impact on major population centres (Sydney, Illawarra, greater Newcastle). It has been generally agreed among the experts the Inquiry spoke to that this was a combination of effective response, perhaps more favourable antecedent conditions, and fewer ignitions,” the report reads.

“Very few whole rural towns and villages were completely consumed by fire. Rather, fire tended to make runs into towns and consume or damage several places, but not generally the whole town.”

The report goes on to acknowledge that ‘large sections of communities in several places” were directly affected, including Cobargo and Batlow.

The report acknowledges that fires have always been a part of the Australian environment, and that “bush fire risks have increased in recent years as a result of climate change, extreme weather events, protracted fire seasons and shorter periods for preparation and planning.”

Despite the emphasis on the unprecedented nature of the bushfire season, the report says that the Black Summer fires are not necessarily the new normal, but an indication of the new extreme.

“Given the evidence that extreme weather events are likely to become more frequent, the State needs to ensure that it is prepared for these ‘unprecedented’ seasons, as well as the smaller-scale localised fires that are seen each year,” the report reads.