Burning questions: how data can help us manage fire

Australia’s relationship with fire is complicated, but data can help us manage it. In this gripping and wide-ranging feature, Bianca Nogrady talks to the researchers at the coalface of this changing phenomenon, asking: What’s known about the science of fire? What data do we have, and how has it changed our approach to fire over the last decade?

To a firefighter, whose fragile skin is protected only by a centimetre or two of heat-resistant fabric, a bushfire is a roaring, leaping beast of flame and fury. It is both unstoppable and unpredictable in its onslaught, a creature of pure physics. But to a firefighter facing that maelstrom in the fullness of its power, a bushfire takes on a living quality, like a dragon rampaging across a landscape, crushing all life and structures in its path.

To a home, built defiantly on land that has been cyclically scoured by fire long before even the Indigenous ancestors set foot on this continent, a bushfire is heat, flame, wind and embers. Atmospheric temperatures can reach 1,600°C, hot enough to melt concrete, glass and steel. The flames themselves are a mere 600°C at their tips, but still carry enough thermal clout to crack a glass window. That heat drives – and is driven by – wind. If the conditions are right, those winds can approach speeds normally associated with major tornadoes. But they pack an extra punch: tiny, red-hot embers that can slip through even the smallest, sub-millimetre-sized gaps to ignite the soft underbelly of a house.

To a nation that has expanded rapidly over the past few centuries in the thin strip of habitable territory between desert and ocean – a strip once lush with forest, grassland and scrub but now sprouting communities, power and telephone networks, homes and offices, roads and highways – a bushfire is a flaming spear hurled into the complex engine of modern civilisation. It disrupts everything with smoke, chaos, panic and tragic, expensive loss. It is a thing to be feared, and increasingly so with the climate change brought on by the combustion of fossil fuels.

But to a gnarled and warty old man banksia, its boughs heavy with woody seed pods, a bushfire is the necessary catalyst for reproduction. Heat and flame trigger the pursed-lipped seed pods to open and spit out their precious cargo. Those seeds land in a soft bed of nutrient-rich ash cleared of competitors, equipped with everything they need to grow and flourish.

For tens of thousands of years, humans and ecosystems on this unique continent have learnt to live with bushfire as a healthy and necessary feature of the landscape. But colonisation, and now climate change, have profoundly altered that relationship in ways that Australia is only just starting to come to grips with. As the planet warms and patterns of rainfall shift, the timing, frequency, distribution and intensity of bushfires are shifting too. Everyone from fire ecologists and pyrogeographers to town planners and engineers are working to understand how this changing relationship will impact all forms of life on this continent, and how we can prepare and adapt for it.

These responses have to be informed by data. To adapt, we need to understand how, when, where and why bushfires occur, property and infrastructure are affected, people are injured or killed, and ecosystems are damaged. The constantly shifting landscape of climate change – rising temperatures, worsening droughts and longer, more intense bushfire seasons – has added a new urgency to the scientific quest to help Australia renegotiate its relationship with fire.

Fire

A flame has simple needs. Give it energy (heat), fuel and oxygen – the so-called “fire triangle” – and it will live. Remove any one of those three elements, and it will die.

But that trifecta alone isn’t enough to explain how and why a single flame swells into a deadly fire storm. Instead, fire scientists look to the ‘fire behaviour triangle’: topography (the lay of the land), weather and fuel. These factors decide whether a single flame becomes a bushfire, how big that fire becomes, where it moves and how fast it travels.

“When you think about the bushfire, its main feature is that it’s a free-spreading fire on the landscape,” says Miguel Gomes Da Cruz, a bushfire behaviour scientist at CSIRO. “What has been always my aim is about how can we better predict this movement, how the fire responds to wind, availability of fuels and so on.”

Topography is perhaps the easiest of the three factors to work with, because it’s easy to map and it doesn’t change unpredictably. Fire travels faster uphill, and the steeper the slope, the faster it moves. A general rule is that for every additional 10 degrees of slope, fire moves twice as fast.

Weather is more complicated, because it includes humidity, temperature, wind and rainfall. But those factors are at least measurable and to some degree forecastable, even as they change over time with climate change.

Fuel is where things get really tricky. It’s difficult to measure accurately, varies enormously even over short distances, and is constantly changing. But fire science is getting better at understanding fuel. In the 1960s, CSIRO fire scientist Alan McArthur developed the Forest Fire Danger Index, a measure of the potential impact of a bushfire on any given day, in any given place and conditions. That index underpins our current Australian Fire Danger Rating System, which is familiar to most as the colourful semi-circular warning signs dotted across the roadscape.

Climate change has added a new urgency to the scientific quest to help Australia renegotiate its relationship with fire.

But this system has undergone a massive overhaul in the last decade, informed by half a century of fire behaviour research. One of the biggest changes is to the variety of fuel types; while McArthur’s original calculations only took two fuel scenarios into account – grassland or forest – the new system considers eight, including spinifex, mallee heath, pine and grassy woodland. This allows a much more accurate forecasting of the fire danger risk in any location based on the landscape – for example, the possibility of fast-moving or tree-crown fire. The updated fire danger ratings also factor in weather; how recently an area has burned; the chance a fire will impact infrastructure, properties and people; and how easy it might be to suppress a fire in that location.

Cruz says that it’s a huge leap forward, but there’s still a way to go. “One of the main limitations we have in knowledge is not about how the fire burns, but how the fuels are mapped,” he says.

Even with the new rating system being more tailored to fuel types, the actual maps of what’s on the ground across the country are still relatively crude and old. That will be improved by a Western Sydney University initiative to create a digital map of the entirety of Australia’s vegetation down to a resolution of five kilometres squared. There’s also research underway to understand how different vegetation landscapes and their fuel potential is changing with climate change.

All of this will be fodder for bushfire models. But as Cruz points out, “one thing with bushfires is that everybody sees them differently”. In the United States, where Cruz completed his masters and PhD, bushfire modelling is driven more by an understanding of the physics of fire. “In North America when they started doing the modelling in the late sixties … they had some mechanical engineers – people that look at wind flow, heat transfer, things like that – and that really guided through decades of research,” Cruz says.

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Fire Weather

Bushfires can generate intense phenomena such as pyrocumulonimbus clouds. As a plume of hot, turbulent air and smoke from a fire rises, it mixes with cooler air and spreads out. It continues to expand and cool as it rises and the atmospheric pressure lowers, until the moisture in the plume condenses and it forms a pyrocumulus cloud. If the conditions are right, this cloud can reach the cold upper troposphere. Cooling ice particles in the cloud build up electrical charge, causing a thunderstorm: a pyrocumulonimbus cloud, or flammagenitus.

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In contrast, in Australia, it’s all about fuel. “In Australia and also in Canada, we have foresters doing the fire research,” says Cruz. That means modelling starts from understanding the underlying fuel situation and how that influences fire behaviour.

Regardless of what perspective bushfire behaviour scientists are coming from, their models need observational data. That comes both from controlled experimental fires, and wild untrammelled ones.

CSIRO’s National Bushfire Behaviour Research Laboratory, perched on the eucalypt­-covered hillside of Canberra’s Black Mountain, houses two unique laboratories to study fire behaviour in highly controlled conditions. The Pyrotron is a 29-metre-long wind tunnel where fire scientists burn carefully prepared and quantified fire fuels, such as leaves and grass, in front of a fan that can generate wind speeds up to 60 kilometres per hour. This allows them to study the effect of wind on the movement of fire and embers. Nearby, a 12-m-tall vertical wind tunnel enables the study of how burning embers behave when transported upwards by wind.

But these conditions are to a bushfire as a home freezer is to Antarctica. So the next step for bushfire experiments is out in the open.

It’s a challenge to collect data in an environment where temperatures can melt glass and steel.

Around 200km south-east of Adelaide, the mallee heath of Ngarkat Conservation Park is the largest area of remnant native vegetation in South Australia. It’s also a site that has provided a wealth of data on how fire behaves in mallee heath and scrubland, through the controlled ignition of experimental plots across the landscape. Each of these experimental plots – ranging in size from around 250–750 sq.m – are dotted with 1- or 2-sq.m sites, so researchers can measure the fuel load and structure in detail. That involves sorting, weighing, sizing and even assessing the moisture content for every bit of fuel in those sample patches. Air temperature, humidity and wind speed are also carefully recorded.

When a plot is set alight, fire behaviour observers in close proximity to the flame front – not a job for the faint-hearted – record at regular intervals characteristics like flame depth, height and angle, whether spot fires are igniting ahead of the fire front and whether the flame burns up into the crowns of trees.

These controlled bushfire experiments are constantly taking place around Australia, in different locations, different conditions and over different time periods. Lighting a fire on total fire ban days, even in a controlled setting, requires a fair bit of trust with local fire authorities – but as Cruz says, “if you want to get the data that matters, that’s when you need to burn”.

But controlled bushfires are still a far cry from the real thing, so bushfire behaviour modelling also needs data from the coalface. Every bushfire is now a source of data, whether from direct observations of firefighters on the ground, aerial footage in visual and infra-red, post-bushfire surveys of damage or even satellite data. It’s a challenge to collect data in an environment where temperatures can melt glass and steel, where embers can spark new fires kilometres ahead of a fire front, where thick plumes of smoke can obscure even infrared sensors, and where firefighting agencies’ need for unfettered access to the skies rules out the use of unmanned aircraft such as drones. But as technology advances, so does the ability to collect data from even the most dangerous fires.

This data then informs models that are becoming ever more sophisticated and accurate in their ability to take the pulse of the landscape, weather and fuel load, and predict when, where and how bushfire will strike. But climate change is moving these goal posts. Bushfire models are therefore being designed with the flexibility needed to take into account that vegetation landscapes are altering, fuels are getting drier, rainfall is becoming less predictable, heat waves are becoming more extreme and wind patterns are shifting.

“To the degree that we understand climate change, we’ve got a reasonable handle on its implications for discrete fire behaviour at a point,” says CSIRO bushfire scientist Justin Leonard. But there are still surprises, he adds – like the duration of the Black Summer bushfires and a fire season “that’s not defined by the worst couple of days within it, but by the fact that there wasn’t actually weather that allowed the fires to go out, even with the support of the fire agencies”.

“It’s like, ‘Well, gee, that wasn’t part of the modelling assumptions’,” Leonard says. “So you’re actually having to learn those lessons, and then go back and unpack the weather and the way we interpret it in new ways to actually deal with it.”

Humans

In a single, terrible day in 2009, 173 people died from bushfire. Black Saturday – 7 February – was the deadliest-known bushfire day recorded in Australian history. Months of hot, dry conditions and record-breaking heatwaves in Victoria had sucked the moisture from the landscape. When sparks from power lines and human hands ignited flames, the resulting blazes ravaged 450,000 hectares of land and 3,500 buildings in just 24 hours.

More than a decade later, the Black Summer spanned almost the entirety of the spring and summer of 2019 and early 2020, from the first major bushfire outbreak at Gospers Mountain in NSW on 26 October 2019 to the three-day ^­torrential rainstorm starting on 7 February 2020 that extinguished most of the bushfires threatening the east coast.

During that time, bushfires burned through more than 24 million hectares – an area slightly smaller than the United Kingdom – destroyed more than 3,000 buildings and incinerated over a billion animals and birds. Thirty-three human lives were lost.

Given the scale of the fires, and their incursion into populated areas such as the NSW Blue Mountains and Mallacoota, Victoria, the fact “that we didn’t end up with [a] Black Saturday-type fatality list is a sign that something is different,” says Richard Thornton, former CEO of Natural Hazards Research Australia, who has been working in the bushfire science field for nearly three decades.

What had changed in the decade between Black Saturday and Black Summer was an understanding of why people died in bushfires, and what could be done to prevent those deaths.

In 2012, a team of CSIRO scientists, including Leonard, analysed more than century of data on human and building loss during bushfire. From 1901 to 2011, 260 recorded bushfires were associated with at least 825 deaths and the destruction of around 11,000 homes. The data came from a variety of sources, including the Australian Fire Authorities Council’s fire fatalities database, ­official inquests, royal commissions, coroners’ reports and even news stories. Its collection was part of a bigger effort to centralise information about house and life loss during bushfires in Australia, into what is now called the Attorney General Department’s National Fire Danger Rating System (NFDRS) Life Loss database.

The richness of that data varied enormously depending on the source. In some cases, all that could be gleaned was that there had been a fatality associated with a fire. But other sources gave information about where the person was when they died – for example, inside a house or car, or out in the open – and whether their death was the direct result of exposure to flame, heat and smoke, or as a consequence of the event, such as from a heart attack or drowning.

The analysis of the century of data revealed one particularly sobering fact: 60% of people who died in bushfires did so within sight of their homes – including 2/3 of those who perished on Black Saturday – and 80% were within 500m of their homes. The numbers suggested a story of many choosing the traditional ‘stay and defend’ approach to bushfire – they stayed to fight, then, as the beast roared nearer, realising they were in mortal peril, they tried to flee, and they died.

The study also suggested that around 2/3 of those deaths happened inside buildings and on days where the conditions met the criteria for what is now labelled “Catastrophic”.

That data, and the reams of evidence presented to the Black Saturday Royal Commission, led to a major shift in the messaging around what people should do in bushfires to keep themselves safe.

“The old ‘prepare, stay and defend policy’ was put under challenge with the Black Saturday Royal Commission,” Thornton says.

But it wasn’t completely defeated.

“It could have ended up that the Royal Commission had said, ‘No, you’ve just got to mass evacuate’ like they do in the United States,” he says. Instead Australia moved towards a middle ground. The message is now that the safest choice is to leave early. But in the case that some still choose to stay and defend, the advice is to be well-­prepared and confident in their ability to keep their head amid the frenzy of a bushfire. The decision to stay or go has to be made well ahead of the bushfire’s arrival, perhaps before one has even ignited if the conditions are bad enough.

60% of people who died in bushfires [from 1901 to 2011] did so within sight of their homes.

And this is where our psychology can be our undoing, particularly the human need to see something with our own eyes to truly believe it. Research suggests that in uncertain situations such as bushfire, people hesitate to act based on a single source of information, even a trusted one. The recent revision of the Australian Fire Danger Rating System down to just four categories (Moderate, High, Extreme and Catastrophic) was informed by a survey of more than 5,000 Australians to better understand how to communicate the risk to lives and property should a bushfire ignite on that day and in those conditions. The new categories – particularly Catastrophic, which comes with tagline of “For your survival, leave bushfire risk areas” – leave no room for uncertainty. Similarly, the revised alert levels – Advice, Watch and Act, and Emergency Warning – are clear in their messaging about the urgency of the threat.

“It’s getting really pointy messaging around ‘now it’s definitely too late to leave the area’,” Leonard says. “That’s a massive improvement and, in a sense, embraces that idea that there’s certain things you can’t control, and you have to actually admit that to be able to issue a warning like that to a community.”

But there is an elephant in the room. Should people be living in areas where these high-level warnings are likely to become more and more commonplace in a hotter, drier Australia?

As an accredited bushfire planning and design consultant at CR Bushfire in Sydney, and former town planner in flood-prone areas of the UK, Catherine Ryland is well acquainted with the threat that extreme weather events pose to infrastructure, especially homes. Her post­graduate dissertation focused on applying the precautionary principle to building in flood-prone areas, and she says, “really basing our decisions less on housing need and housing demand, but more on hazard risk and getting the planning right for the risk base.

“So it was very interesting then coming into the bushfire space 20 years later and encountering very similar issues in the way that risk is dealt with in the planning system.”

When she started working on bushfires, Ryland says everything to do with bushfire ­mitigation was focused at the level of individual buildings and houses, “rather than looking at land release and saying, ‘is that land actually appropriate to build on, and can we mitigate the risks?’ ”

That is starting to change. Both the Black Saturday and Black Summer Royal Commission reports highlighted the need to look closely at the viability of suburban expansions and ensure that new homes aren’t being built in areas where the bushfire risk is too high. Councils are now taking a more strategic view of where and how people build in bushfire-prone areas.

But it’s still a long way from a comprehensive policy, or even from an understanding of what bushfire-strategic land planning looks like.

“There has been a huge amount of change in terms of the way we can model risk for bushfires, so that obviously has given us more information to be able to play with in terms of actually identifying where the risk might be too high for ­certain areas,” Ryland says.

Knowing the risk is one thing. Deciding what to do about it, especially amid a housing shortage, is a whole other issue, and one that local and state governments will increasingly have to consider when deciding where Australians live.

One thing is abundantly clear: after three consecutive years of La Niña, bringing wetter, cooler summers to the east coast, a horror summer fuelled by climate-change-amplified weather systems – El Niño and the Indian Ocean Dipole – awaits. Already the early warning signs suggest that the relationship between Australia’s people and ecosystems, and fire, is about to take a turn for the worse.

Ecosystems

If you can’t beat ’em, join ’em. That’s how Australian plants deal with the inevitability of fire on this hot, dry continent. Fire will come, whether ignited by lightning or human hands, so plants such as the old man banksia have evolved not just to survive fire but to require it. Even Australia’s fauna has learnt to live and even thrive with fire; in the case of the brown falcon, deliberately seeding fires to flush out prey from their grassland burrows.

But just like humans, Australian flora and fauna are facing a new challenge from climate change, which is altering the frequency, intensity and distribution of fire in the landscape.

On 22 December 2019, the Gospers Mountain bushfire burned into Blackheath, in the Blue Mountains. What had been lush – albeit desiccated – sclerophyll forest, thick with the smooth white trunks of mountain ash rising above dense tea tree and banksia shrubbery, became a grey and black moonscape.

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Barely a fortnight later, there were signs of recovery: burgundy-coloured epicormic growth sprouting from the charred bark of a eucalypt, a flash of green emerging from the blackened top of a grass tree.

This bit of Australian bush was lucky. The fire that burned through on 22 December was ­relatively calm, meandering through the dry undergrowth in low winds and mild temperatures. It was also the first bushfire that had burned this ground in many decades. Many regions incinerated by Black Summer were not so lucky.

The concept of a fire regime is key to understanding a bushfire’s impact, says fire ecologist Rachael Nolan from Western Sydney University. “The regime is not just fire, a binary ‘yes/no’,” Nolan says. “It’s how frequent the fire is, how severe the fire is, is it understorey fire or overstorey fire, what season the fire is, how big the fire is – because that could affect if you have little patches of refugia for animals to escape in.”

Added to that list is the question of how fire regimes are changing. This process has occurred since the continent first formed, and in more recent times with the landscape management practices of First Nations people. But now there’s climate change.

“What we can say is that generally a lot of our ecosystems are burning more frequently than they have been with the historical record,” Nolan says, acknowledging that the historical record doesn’t go back all that far.

Bushfire ecologists talk about “interval squeeze”, a term coined in a pivotal 2015 paper published in Frontiers in Ecology and the Environment. It projected that climate change and the associated increase in bushfire, heat and drought would “narrow the fire interval window compatible with population persistence”, meaning that just as plants are requiring longer intervals between fires to recover from more intense fires, those intervals are shortening due to climate change. The paper warned that woody plants, such as eucalyptus, were on a trajectory towards increased extinction risk, especially in areas forecast to become warmer and drier.

Eight years later, one of its co-authors – David Bowman, a professor at the University of Tasmania – is watching those predictions come true. The Victorian Alps, for example, have burned twice in the past decade while also dealing with drought, and the combination is taking a visible toll.

Unlike a house or a community, it’s difficult to protect an entire forest or ecosystem from bushfire.

“The trees are really on the ropes, and these are the notoriously tough eucalypts,” Bowman says. “There’s a lot of dead trees.”

Bowman believes it’s evidence of ecological collapse, and that’s just one example. “Some vast percentage of the world’s eucalyptus forests [are] in this amazingly precarious state, and now we’re going into an El Niño with climate change and [a positive] Indian Ocean Dipole,” Bowman says. “It’s terrifying.”

Bowman knows better than most how Australian ecosystems are changing with more frequent and intense bushfire seasons coming on the heels of droughts and heatwaves. As a pyrogeographer – a title he co-opted after being accused of being a scientific dilettante “just flitting around doing all this stuff” – he brings his interests in archaeology, anthropology, eco­physiology, climatology, forest ecology, fire ­management, human health, epidemiology (and possibly others) to the challenge of under­standing and adapting to bushfire.

“I needed a framework, and pyrogeography is a framework,” he says. “It’s understanding fire in space and in time, and understanding humans as a central agent, and understanding recursive relationships amongst all the elements of that relationship.”

Bowman’s research spans from studying how bushfire activity has varied across the southern hemisphere over the last 10,000 years, to studying how stalled policy on bushfire bunkers is creating a barrier to fire adaptation.

This involves “lots and lots and lots of field work, lots of analysis, and then there’s a critical point where you have to read incredibly widely, and start absorbing huge amounts of information,” Bowman says. “It involves continent-scale and global-scale analyses in collaboration with experts in fields from molecular ecology and mathematical modelling to geospatial statistics and law.”

Alarmingly, his work has revealed that in response to climate change, the Australian bush is experiencing a sort of wildly oscillating adolescence.

“Because the climate’s changed, the amount of carbon in the landscape – which is the fuel – is disproportionate, it’s in disequilibrium, and so that has to be removed in some way,” Bowman says. “The simplest way to remove it, because of climate change, will be through fire.”

Fire is something that we’ll always be challenged to better understand, respect, embrace, evolve with.

Woodlands, like the eucalypt forests of the Blue Mountains, are likely to undergo increasingly traumatic and extreme boom-and-bust cycles of regrowth and fire, but what comes at the conclusion of that – what equilibrium will look like – is likely some form of ecological collapse that will produce a very different vegetation landscape.

What will happen to any particular forest is an open question, but some warning signs are emerging, according to Nolan. “We’re not seeing eucalypt species going extinct or anything like that – it’s more that the structure of the vegetation or the way it looks is changing,” she says.

If that sounds benign – like the forest simply rearranging the furniture – it’s not. As forests change, becoming less dominated by large trees and shifting towards smaller trees, shrubs or even grassland, that ecosystem’s ability to store carbon plummets.

Unlike a house or even a community, it’s pretty difficult to protect an entire forest or ecosystem from bushfire. But across Australia’s northern tropical grasslands, which stretch from the Kimberley in the west to Cairns in the east, Indigenous rangers, pastoralists and scientists are, quite literally, fighting fire with fire.

Indigenous cultural burning practices are returning to these landscapes, and non-­Indigenous Australia is learning from them. As the fuel loads in the vast savanna grasslands build up, so-called ‘cool burns’ are being used to get these areas under control early in the fire season, when moisture ensures the fires will be less intense and easier to control.

But choosing where to do cool burns in such a vast landscape to maximise the benefits is difficult. NAFI – the North Australia and Rangelands Fire Information website – provides one solution. Run by Charles Darwin University (CDU) since the early 2000s, NAFI is a near-real-time fire-mapping resource that uses satellite data to create maps of areas that are burning or have burned, down to a resolution of around 250 sq.m per pixel, with higher resolution in some areas.

“Anybody who really is interested in managing these large areas of land that are in this open country needs to know where the fires are and what areas have been burned,” says Peter Jacklyn, a tropical ecologist and NAFI Service Coordinator at CDU. “If it’s been burned yesterday, there’s not going to be much grass there at all; if it burned three years ago, there’s going to be quite a bit.”

Those burns may be the result of bushfires, cool burns by Indigenous rangers and custodians, by landowners, or by fire or parks authorities. Those groups use NAFI to plan when and where to burn to reduce the risk of the big, intense, greenhouse-gas-spewing bushfires of late summer. Cool burns can be used to protect vulnerable areas and ecosystems by creating low-fuel barriers around them, and they are also a source of carbon credits if they then reduce fire emissions overall.

“Across that far northern belt of Australia, the frequency particularly of fires that occur late in the dry season … has dropped right off and these are where these carbon projects are,” Jacklyn says.

Here, fire is a tool: one that can be used to nourish landscapes in the way it has been done for tens of thousands of years.

Looking forward

The relationship between Australia and fire is not over. It never will be. It might be going through a tough time right now, but that will change again as science, society and culture seek to find some sort of equilibrium in a system in flux.

Over the course of a decades-long career in bushfire science, CSIRO’s Leonard has observed and studied that changing relationship. “It’s actually an inevitable and important aspect of the environment we live in and something that we’ll always be challenged to better understand, respect, embrace, evolve with,” he says.

Fire only cares about three things: energy, oxygen and fuel. It won’t change as long as the laws of physics still hold. It’s humans, living in the Anthropocene – and the Pyrocene – who must adapt. And we are.

“From a societal perspective, I see [us] slowly transitioning from ‘we can conquer it, we can conquer anything as a society and all we need is the right amount of resources and clever ways to activate it and get on top of things’,” Leonard says, “moving to a reality where you recognise that it’s not possible to completely control [fire] and that a holistic approach is needed to manage, prepare for, limit the destructive nature of, and utilise it as an effective tool.”