By Dr Catriona Nguyen-Robertson MRSV

This article follows a presentation to the Royal Society of Victoria on 13th July 2023 titled “Decolonising Fire Science”, delivered by A/Prof Philip Zylstra (Curtin University), in conversation with Wurundjeri Elder, Uncle Dave Wandin.

The people of the Kulin nation – the Traditional Owners of Naarm (Melbourne) and the surrounding area – believe that Bunjil, the Wedge-tailed Eagle, created the land. Bunjil’s First Law is that you must respect and look after your mother. Our mothers look after us when we are young, and as they grow older, we, in turn, take care of them. This law does not only refer to our physical mothers, but also to the spirit of our mother: our Country. Mother nature provides us with many resources. ‘When we walk on Country, we’re walking on her body’ says Uncle Dave Wandin. ‘When we swim in the waters, we’re swimming in her veins.’ She is tired and weary, and we need to care for her.

First Nations people have been caring for Country for tens of thousands of years. They have been and continue to be scientists, observing the land, water, and sky to gain knowledge and understanding. However, it has taken a long time for this knowledge to be regarded as “science”, simply because it doesn’t fit with European ideas of the scientific method or knowledge dissemination. ‘We didn’t write books – we read Country,’ says Uncle Dave.

Only by walking Country together with the land’s Traditional Owners – and cooperating with the land itself – can we heal Country together.

Australia’s landscape of fire

The gradual drying of the Australian continent over tens of millions years has nurtured a landscape prone to fire.¹ It has the right conditions for fire: wet enough for things to grow, and dry enough for them to burn. Over time, animals and plants adapted. And over millennia, First Nations people also developed sustainable fire regimes.

Remote area firefighter-turned-ecologist, A/Prof. Philip (Phil) Zylstra, realised that fire management has become entrenched in discredited ideas that do not reflect reality and can lead to poor decision-making. He argues that poor colonial fire science reinterprets First Peoples’ knowledge to justify prescribed burning regimes that decimate carbon storage, threaten the existence of many species, and deepen the catastrophic impact of bushfires.

Current fire management by government agencies focused on prescribed burns to reduce fuel loads are presented as vital to limiting the spread and intensity of bushfires. The idea is that bushfire fuels are made up of leaf litter, twigs, and bark that burn and carry a fire. Reduce the fuel load, and we reduce the spread and intensity. These prescribed fires are said to mimic First Nations peoples’ cultural burning practices, however, Phil points out that this is not quite the case. The use of fire in healing and managing Country is much more complex.

The complexity of First Peoples’ Knowledge

‘It is often said that First Peoples’ knowledge was lost. But we need to be more brutal: it was stolen and taken,’ says Phil. But some knowledge remains in the culture of survivors and in the landscape itself, ‘like seeds waiting to grow’.

Uncle Wayne Webb and his son, Iszaac, are the last two speakers of the Wadandi language, holding onto their knowledge of the tall red tingle forests. Red tingles are among the tallest eucalypts, growing up to 70 metres. They grow only in a 6,000-hectare stretch along the south coast of Western Australia. The Menang and Goreng Traditional Owners of these forests say that fire should be used in specific locations, burning only what is needed in small, strategically placed patches. They are aware that tingle trees regenerate well after fire, but are sensitive to frequent fires, no matter how mild. Flames can enter the tree and hollow it out – and the next fire will cause its collapse. Uncle Wayne advised government agencies that Traditional Owners deliberately exclude fire from tall red tingle forests – but those agencies, in turn, claim to be following cultural burning practices with their prescribed burns. Surely it would be Uncle Wayne who would know what the cultural burning practices for that area are.

First Nations people have detailed, complex knowledge of the landscape, having observed it over millennia. Each local language group cares for their Country using fire as a tool according to their own laws and philosophies. They know their Country. As Uncle Dave points out, ‘you know the stories and connections in your Country. You know where fire belongs. If you are coming into someone else’s Country, you come in as an infant.’

“Settler mimicry” burning practices and debunking the “science” behind it

The most immediate problem with the idea of settler mimicry burning practices is the term. “Settler” is a gentle term – after all, ‘we tend not to talk about an asteroid settling among the dinosaurs,’ says Phil. Secondly, it suggests that “settlers” learned and copied the practices of Traditional Owners, however you cannot learn 65 thousand years of knowledge by merely watching.

European farmers observed cultural burnings and started using fire themselves. They wanted the benefits of having more green shoots following the low-intensity burning of grasses to feed their livestock, as well as the prevention of trees bouncing back on their newly established grazing lands. It was the beginning of prescribed burns.

Prescribed burns, or fuel-load reduction, is based on the idea that the amount of fuel in a forest determines how flammable it is. The idea comes from fire behaviour modelling – for entirely different trees – imported from the United States in the 1960s. Europeans wanted science to support their processes, and a simple equation published by an American fire researcher fit the bill: a fire’s heat output (or intensity) is equal to the amount of energy stored in the fuel, multiplied by the amount of fuel, and multiplied again by the speed the fire spreads and consumes it.²

The argument that fuel-load drives the rate of spread in Australian forests was based on nine data points in a leaflet.³ They stated that if we halve the fuel load – the leaf litter on the ground – we can halve the speed of fire. This data was never backed by evidence, but in the absence of something better it became the foundation of Australian fire management.

But in 1999, Neil Burrows disproved this idea that fuel-load drives a fire’s rate of spread. In both laboratory experiments and in the field, he found that the rate of spread of fire in Jarrah Forest was independent of fuel quantity.⁴ Over 20 years later, CSIRO’s Project Vesta conducted more experimental burns in the dry eucalypt forests of southern Australia to further support this finding.⁵ What is generally considered “fuel-load” – debris on the ground – could only drive low-intensity fires with small flames. Finally, infra-red line scans of many bushfires in diverse forests showed that fuel load had little influence on the rate of spread of those fires.⁶

A second outdated argument for prescribed burns is that ‘fuel-load and rate of spread together drive fire intensity and thus the impact of fire’. Project Vesta, however, demonstrated that the forest understorey drives fire behaviour more than any other component of the forest.⁵ The issue is not how much leaf litter or bark is present, but whether flames will span the gaps from burning fuel on the ground to ignite plants higher up.

Project Vesta showed that it is more about whether shrubs are present, as they are better able to carry a fire forward and higher compared to leaf litter on the ground. The understorey of red tingle forest consists of tall shrubs that become less dense as they age. As the understorey ages, the lower branches of taller plants “self-prune”, shedding their dead leaves and twigs. Phil and his colleagues developed a fire modelling tool to understand how this impacts fire behaviour; when this litter is on the ground, it begins to decay and poses a much lower fire risk than if it were still higher up.⁷ Further, allowing forests to age – without regularly burning them – allows the lower plants to grow into tall plants that act as a shelter to slow the wind and calm the fire.⁸ Given that many native flora species evolved in a fire-prone landscape and adapted to require fire for effective germination, regular burns encourage dense understorey regrowth. Phil argues that this is more of a risk for future devastating fires, as it provides more low-lying plant matter to burn.

Poorly managed prescribed burning can lead to catastrophic outcomes, including the decimation of critically endangered wildlife populations when controlled fires escape their containments. Phil documented the annihilation of 77% of the Western Ringtail Possum (Pseudocheirus occidentalis) in Warrungup Spring bush reserve in 2018.⁹ The possum – or ngwayir in the language of Traditional Owners – is critically endangered and only found in a small patch of southwest Australia. When fires rage through, the air around tree hollows can approach 500 °C – if possums and other arboreal animals hang around, either they or (at the very least) their respiratory tracts will burn. Phil urges us to move away from bad fire science to prevent similar tragedies.

Moving forward

The fire “science” behind prescribed burning practices has been largely debunked. Instead of burning large areas of forest to reduce fuel loads, the evidence is clear: we need to cooperate with vegetation. The regrowth period of dense understorey in forests tends to be when flammability is the highest. By letting forests age over time, they self-thin and become less likely to burn. Prescribed burning disrupts this process, and current practices need to be halted.

In addition, we need to listen to First Peoples. Cultural burning practices are precise and focused. Unlike with prescribed burns, Indigenous fire practitioners like Uncle Dave do not attempt to burn vast areas at once. They carefully control what burns, when, and where, cooperating with and reinforcing natural processes such as self-thinning, so that Country is allowed to age. Listening to Phil, Uncle Dave is happy to see modern science catching up and backing up what First Peoples have always known. You need the ‘right fire, for the right Country, at the right time,’ he says. And Victoria is catching on – Uncle Dave is a major contributor to the Victorian Traditional Owner Cultural Fire Strategy launched in 2019 that supports Traditional Owners to practise cultural burning and ensure knowledge about fire is sustained through generations.

Australia’s forests have controlled their own fire risk for millennia. We should respect, rather than disrupt, these ancient natural processes. We need to stop thinking of ourselves as separate from the ecosystem. We should cooperate with Country rather than try to dominate it, because we are part of it.

You can watch Adjunct Associate Professor Philip Zylstra’s presentation at: youtube.com/watch?v=ahilyWGPd1c

This piece appears in the September 2023 edition of Science Victoria magazine. All issues can be read online for free at rsv.org.au/Science-Victoria.

References:

1. Crisp, M. D., et al. (2011). Flammable biomes dominated by eucalypts originated at the Cretaceous–Palaeogene boundary. Nature Communications, 2(1), 1–8. doi.org/10.1038/ncomms1191
2. Byram, G. M. (1959). Combustion of Forest Fuels. In Davis, K. P. (Ed.), Forest Fire Control and Use (pp. 61-89). McGraw-Hill Book Company.
3. McArthur, A. G. (1967). Fire behaviour in Eucalypt forests. Forestry and Timber Bureau Leaflet 107. In: 9th Commonwealth Forestry Conference p. 26 Canberra, ACT.
4. Burrows, N.D. (1999). Fire behaviour in Jarrah forest fuels: 1. Laboratory experiments. CALMscience 3, 31–56.
5. Cruz, M. G. (2022). An empirical-based model for predicting the forward spread rate of wildfires in eucalypt forests. International Journal of Wildland Fire, 31(1). 81-95. doi.org/10.1071/WF21068
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8. Zylstra, P., et al. (2023). Mechanisms by which growth and succession limit the impact of fire in a south-western Australian forested ecosystem. Functional Ecology, 37(5). 1350-1365. doi.org/10.1111/1365-2435.14305
9. Zylstra, P. (2022). Quantifying the direct fire threat to a critically endangered arboreal marsupial using biophysical, mechanistic modelling. Austral Ecology, 48(2). 266-288. doi.org/10.1111/aec.13264