Cool fire: Unlocking the secrets of Aboriginal land management

It’s field-based research that I love. Getting out on Country. My parents used to remark that as a kid no toy of mine ever lasted a week before I’d be pulling it apart and trying to put it back together. I just love knowing how things work, and that extends into the world around us – trying to understand how our environments work, and what the dynamics are.

My coring devices are personal designs that I’ve hodge-podged together from different equipment. If you’re working in a lake, you’ll need a drilling rig that can handle the sloppy sediments, but also retrieve a column of sediment from the bottom of the lake, and these can be 50-100 metres deep. Or if you’re on a bog, you’ll need something that you can operate handheld to push down into the peat and slice out sections.

It’s also got to weigh under 400kg so that the lightest range helicopter can move it, it’s got to be easy to erect, but then strong enough to lift out sometimes very heavy material out of the bottom of these deep lakes.

Once you’ve managed to get out an undisturbed column of sediment, you then need to package the material up and return it to the laboratory. We mostly sample into polycarbonate tubing, which we split longitudinally back in the lab to give us a perfectly straight surface. We then take our cores to ANSTO – the Australian Nuclear Science and Technology Organisation – for scanning.

There we use a micro X-ray fluorescence scanner (Micro-SRF), which shines a molybdenum powered light source onto the sediment surface, which excites the atoms. They begin to vibrate and re-emit energy, and the re-emission wavelength is dependent on the atomic number. You get an elemental profile every 100 microns down your sedimentary sequence. This can tell you all sorts of things.

“What we see from our work is that there’s very few, if any, parts of Australia that could be called wilderness.”

The other half we slice in 5mm increments, sometimes even finer, and use chemical washes to isolate certain fractions, which we call proxies. A proxy is simply something that stands in substitute for something else, so pollen traces, for example, is an indicator of vegetation, charcoal is an indicator of fire, diatoms are an indicator of water quality or water dynamics. Whatever your interest is, there’s a large array of proxies you can isolate within each segment.

With the pollen, you extract it and count it under a high-powered microscope. You then marry that with your charcoal contents, and with each of those little slices you can start to understand fire-driven vegetation change.

Colleagues have also been developing a technique using single Fourier Transformed Infrared Spectroscopy (FTIR). With the right calibration set, we’re able to now determine the temperature of the fire that created each charcoal fragment. Previously, that was a big unknown, but we now understand it can be due to changes in vegetation type – woody plants produce more charcoal than grasses, for example.

The last Ice Age fully ended by 11,900 years ago, when we entered the era called the Holocene – basically a geological epoch where climate has been variable and dynamic, but relatively stable on a global geological scale. That was a huge reorganisation that drove massive changes in global vegetation. The 12,000 years since then has been marked by a lot of relatively small-scale events – until contemporary climate change.

But since that exit from the Ice Age, the single biggest event we see right across Southeast Australia has been the removal of Aboriginal management of the land following the British arrival here. The biggest and most ubiquitous shift has clearly been the cessation of cultural burning.

We see fuel loads increase as trees and shrubs increase in density. With that comes the onset of bigger and more severe fires. Geochemical data then tells us we’re seeing a lot of postfire erosion that just wasn’t there previously.

This is forensic work – there were a lot of unknowns there that we had to triangulate with lots of other lines of evidence to reduce the range of explanations to account for those co-occurrences. But this allows us to test the difference between cultural burning, being cool burning, versus catastrophic bushfires, which are very hot burning. It’s going to empower us to start asking some of those critical questions about what kind of temperature fires Aboriginal people were using to maintain the biodiversity that we’re now losing at a rate of knots.

“There’s a growing realisation that we need this Aboriginal knowledge and information if we are to operate sustainably on Country – that this ancient know-how needs to be reawakened.”

Importantly, this information helps us to understand that the concept of “wilderness”, as we have come to know it, is a myth. Full stop. Work being produced here and overseas shows that less than 20% of terrestrial Earth, including areas of ice, has been unaltered for the last 12,000 years. Since the last Ice Age, humans have had a profound influence on global dynamics. This has now been quantified to show that the vast majority of the Earth has been altered by humans in some way. This concept of “wilderness” is very much a cultural one, with British origins.

What we see from our work is that there’s very few, if any, parts of Australia that could be called wilderness. Sure, there are pockets of rainforests – Aboriginal people didn’t burn every inch of the content, but worked to protect some areas and manage others.

This modern notion of wilderness denies the management of Country by Aboriginal custodians for all those thousands of years. And as we are seeing, if we remove that Aboriginal management, ecosystems collapse. The very biodiversity that people are trying to protect by calling these areas “wilderness” has in fact been dependent on human activity, dependent on Aboriginal management. In many ways, the conservation movement is perpetuating a lot of the environmental problems that they’re seeking to resolve.

“The next big thing we can do is actually sit down and give people the space and confidence to share their knowledge and be happy for that to be used in ways to heal Country.”

There’s a growing realisation that we need this Aboriginal knowledge and information if we are to operate sustainably on Country – that this ancient know-how needs to be reawakened. But there’s an understandable reticence in Aboriginal communities to share this knowledge, as for so long shame or punishment has been attached to expressing language, knowledge and culture. Aboriginal people will need the space, comfort, security and safety to feel they can actually express and share their knowledge.

Science has a role in backing up and supporting traditional knowledge, filling in gaps where there may be some. But the next big thing we can do is actually sit down and give people the space and confidence to share their knowledge and be happy for that to be used in ways to heal Country.

As told to Graem Sims.

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