Australia’s catastrophic bushfire season this year has raised a lot of questions. Dr Philip Zylstra discusses the phenomenon of Australian bushfires and strategies we can employ to reduce forest flammability.
With the catastrophic summer bushfires in Australia’ eastern states still front of mind,prescribed burning has become a contentious topic – some scientists argue for an increase in the regime, while others are concerned about the impact on the bush ecosystem.
In The Future Of Bushfires, we hear the opinions of Dr Phillp Zylstra, an adjunct associate professor at Curtin University, whose research focuses on the drivers of fire behaviour, flammability and modelling bushfire risk.
Dr Zylstra has developed modelling on dynamic fire behaviour that calculates the capacity for flames to ignite new leaves, branches or plants, and jump across the spaces between them.
In this episode, Dr Zystra gives context to prescribed burning of Australian landscapes, raises questions on the effectiveness of current fire prevention strategies and discusses how our methods vastly differ from traditional Aboriginal fire practice.
Curtin University supports academic freedom of speech. The views expressed in The Future Of podcast may not reflect those of the university.
Music: OKAY by 13ounce Creative Commons — Attribution-ShareAlike 3.0 Unported — CC BY-SA 3.0 Music promoted by Audio Library
You can read the full transcript for the episode here.
Intro: 00:00 This is, The Future Of, where experts share their vision of the future and how their work is helping shape it for the better.
David: 00:10 I'm David Blaney. As we know, the summer bushfires in Australia's Eastern States and indeed across the country are unprecedented. One of the ways we try to lessen the impact of bushfires is through prescribed burning. To discuss this topic with me today is Dr Philip Zylstra, an adjunct associate professor at Curtin University. Thank you very much for coming in today, Philip.
Dr Zylstra: 00:35 Thank you.
David: 00:36 Phillip, your main research interests are in the flammability of Australian forests and how plant traits impact the severity of fires. Is what we're doing in terms of prescribed burning? Is it working and what should we be doing differently?
Dr Zylstra: 00:55 It's a complex question because it depends on what you consider to be working, what you want to measure it by. The simplest answer I would say is no, it isn't working. There are some who would say that it's reducing the severity of bushfires in those areas and there is some evidence that it is in very recently burnt patches. But if we want to look at questions such as: is it helping us save houses? At the moment we've got no evidence to say that it is, except in very specific circumstances where we have prescribed burns very close to homes. In those instances we've got a small measurable effect of prescribed burning. Is it reducing the area of fire impact or the frequency of fire impact on the landscape or its impact on, on different species carbon balance in the landscape? The evidence at this stage says that it's probably increasing that.
David: 02:01 Why do we, well, actually first of all, what exactly is a prescribed burn and how do they work and why do we do them?
Dr Zylstra: 02:13 So prescribed burn is just a, it's a controlled fire that we light in conditions where we believe we'll be able to contain it. It's lit to a prescription, which is a set of weather conditions in a lighter pattern that will, we intend cause the fire behavior to be within a certain set of bounds so we can contain the fire. The ideal is that it's not escaping and burning down houses and causing destruction, but also we're aiming to keep, say, flame dimensions within a certain range so that we're we're minimising tree scorch and minimising damage to wildlife and particular species. So that's the prescription. It's a set of weather conditions and and a [inaudible] pattern you can control a lot with the way that you light a burn. And the reason why we do them is because we have a, I suppose it's an assumption that we've had since the 1960s that a forest is effectively like an accumulation of fuel, like a, like a campfire. As you, if you burn the forest, you remove some of that fuel and then over time that fuel returns to the forest and the forest becomes more flammable over time. And so, so our ideal is to, is to stop that forest from reaching its high level of fuel accumulation and allow us an area where any subsequent bushfires might be a bit more controllable.
David: 03:57 And where did this, obviously this assumption didn't just appear out of thin air. Where did this assumption come from and what does the evidence or what does what we know now say about that assumption?
Dr Zylstra: 04:13 It's come largely as a cultural thing to start with. Burning landscapes was an English cultural way of managing land. So in England, you think of the moors, I believed for most of my life that the moors were just a natural landscape up there, but they were actually created over quite a few thousand years by people burning forests to clear them, to create grazing land. That accelerated over time and it reached a peak in around the 1830s, 1840s, when English migrants started coming to Australia and they carried out that same approach of trying to convert Australian forest and Australian landscapes into landscapes that were suitable for grazing English animals. And so they brought fire with them as a way of doing it. And they often looked around at our First Nations and saw them using fire, but there was very little respect for those nations as we know, it was an invasion.
Dr Zylstra: 05:24 So nobody really much took the time to stop and learn exactly what they were doing with fire, which was very, very different from land clearing. So it was just assumed that that's what they were using it for. So we've had a century or more of that sort of management and during that time there was always the observations if an area has just been burned very recently often a bushfire will stop there. And so there was an understanding that this is a way of stopping bushfires and it's quite a valid observation. Obviously if you've just burned an area and you've got bare soil and you've burned away all the plants, then a bushfire is most likely to stop there. Not guaranteed, but it is likely. So that was the background to it. Then in the 1960s, a CSIRO scientist Alan MacArthur started doing work where he conducted, the estimates are up to something like 700 experimental fires, mostly around Canberra, but some in the Jarrah forest over here.
Dr Zylstra: 06:30 He formulated an idea that said that the intensity of a bushfire or the speed that a bushfire spreads particularly is proportional to the amount of leaf litter on the ground. And that has since then been the foundation of fire management in Australia, where when we talk about fuel reduction burning it's about reducing the amount of leaf litter on the ground. So where we've come since then is MacArthur's work, he only ever published it in a leaflet, it never went into a scientific publication,
David: 07:10 So it wasn't peer reviewed?
Dr Zylstra: 07:11 Never peer reviewed, no. He published nine hand drawn dots on a graph in a leaflet. And they were accepted very widely, you know, at the same time he also published other leaflets saying, look, this is effectively my first guess. It may be completely wrong.
David: 07:27 Not exactly a solid foundation for us to be basing decades and policy on.
Dr Zylstra: 07:34 No, no, not at all. And since then it's been investigated. There's in particular, the most outstanding investigation of it was Dr. Neil Burrows from WA who in the 90s, for his PhD, formally replicated those experiments, you know, in a, in a proper scientific setting and concluded there was absolutely no relationship between the weight of leaf litter and the speed that a fire spreads. So he thoroughly falsified the idea. His work was largely ignored and a little bit demonized really to be fair. I think he yeah, I can imagine it wouldn't necessarily have been easy for him at the time, it's kind of holy writ it's become to talk about fuel reduction burning. But there's been other work since then that has again, examined the questions and never yet have we found a single experiment that has supported MacArthur's first guess.
Dr Zylstra: 08:40 My own work was to start from scratch and look at exactly what does drive a fire. And so a few years ago I published a model that uses a mechanistic approach instead of a whole series of experimental burns. And what I showed is that it's the composition and the arrangement of the plants. You get big fires when plants are burning. Basically. It wasn't that complicated after all.
David: 09:10 This fuel hypothesis isn't really sort of born out in reality, If not fuel then what? And you had mentioned the arrangement and the types of plants.
Dr Zylstra: 09:33 So it is fuel, but the problem is that we use the word fuel as a kind of a code word.
David: 09:33 So we think of like a tank of fuel, like the quantity of fuel rather than like what, what that actually ...
Dr Zylstra: 09:33 Yeah, so fuel ultimately fuel is anything that that adds to the flame, that that gives you a more intense flame. So, so the fuel could be the leaf litter on the ground, but then it could also be the shrubs or if you've got a crown fire, then it's also the trees. So the amount of fuel actually varies depending on the fire. If you've just got a fire burning through leaf litter on the ground, then you have small flames. If it's igniting the shrubs, you have much larger flames and so on. So, the thing is that's confused the issue is that we've kind of got a little bit of doublespeak in there. When we talk about fuel, it's not about having whether you have a lot of fuel or not. It's about whether the fire can ignite that fuel. Because what happens with a plant community when, when you burn a forest is you yes, immediately you do remove a lot of those plants.
Dr Zylstra: 10:33 You remove the leaf litter on the ground, but you also germinate a whole lot of plants. You germinate shrubs, you cause often trees to resprout from the ground or you know, new saplings to grow. And what happens is, by scorching the higher plants and encouraging growth at the bottom, you can actually make that forest much more flammable. And the reason for that is that plant foliage that's out of the reach of the flames can't be ignited. It's no longer fuel. If you think of say tall karri forests, if that folliage is 50 metres above the ground, then there's almost no chance it's going to catch on fire. And what it's doing while it's up there is slowing the wind speed and that slows the fire down on the ground. But if you were to burn a forest where the foliage is out of reach of the flames, you burn that and then produce a whole lot of shrub growth.
Dr Zylstra: 11:30 And in karri forests, again as an example, we know that we get plants like karri hazel, that are germinated by the fire and they grow extremely dense on the ground and those plants get taller over time. And so for the first couple of years, there's not much there to burn. Those plants are very small. You've got bare soil underneath them, but then the leaf litter comes back, the plants get taller, you get much taller flames as those shrubs ignite. And then eventually those shrubs get tall enough that they become small trees and out of reach of the flames. And then ultimately they self thin, which is a natural ecological process that happens in basically all forests. And you lose that layer there until eventually you get an open understorey. The fuel there has been increased by burning it because you've brought in all of these shrubs, you've caused these shrubs to grow there.
Dr Zylstra: 12:31 But the problem is that those shrubs aren't classified as fuel in our systems. So in Western Australia you use a system called 'the red book' where it's kind of an expert system. Somebody basically wrote the book and said that fuel is leaf litter and fine sticks and things that are close to the ground and they didn't provide any evidence to support that. It was just a matter of 'we're experienced foresters, we know we're talking about, you need to believe us. And we're really at a point now where we can't just take people on their word anymore because they're old and wise. You know, we need to start looking at what does the evidence actually say because we'd been in a situation like that karri forest by saying that shrubs aren't fuel where it causes a completely different management. It says that we've got to keep burning that forest and keep that shrub layer being constantly renewed. So we have a constant dense layer of flammable plants there and I think it's probably exactly the wrong thing to do, but it's all about the codeword, 'fuel'.
David: 13:43 So rather than simply getting out a map, probably not Google maps, we're probably using more advanced tools than that and drawing a line on it and saying, we're going to burn this area. What should we be doing differently?
Dr Zylstra: 13:59 We need to look at individual forests and see how they respond to fire in a much longer term than we have been, We've got areas now, a lot of the Southwest is classed as 'long unburned' if it hasn't had fire for six years. Now in the life of plants and the forests, that's no time at all. If you look at the Western Woodlands they're still in a regrowth phase for the first 150 years. So we need to start understanding how those dynamics change within an individual plant community and look and see as those forests age, do they reach a point where self-thinning makes them less flammable?
Dr Zylstra: 14:47 And we know that prescribed burning can help us to some extent if it's done close to buildings. It's not hugely effective, particularly if conditions get very hot, very windy, it's basically got no effect. We've certainly seen that in the Eastern States where those bushfires, occurred at the peak of a record period of prescribed burning for national parks in New South Wales. And yet those fires just burnt straight through all of the recent prescribed burns as if they didn't exist. So we know that they're very limited, but they can be helpful if they're close to assets. So we need to focus that burning close to assets rather than burning huge remote areas. And then because there has been a long history of burning that has now put the whole broad landscape of the Southwest, so much of that now is in a very flammable state.
Dr Zylstra: 15:50 We need to start looking at strategies for getting those areas past that hump to where those shrubs start to self thin again and getting to a less flammable state. And a lot of that will involve investing resources into what we call 'rapid attack' where as soon as there's a lightning strike, you have people straight on the ground. And in New South Wales, I was what we call a remote area firefighter. They're a [inaudible] team where they'd fly us in by helicopter, they'd lower us on a winch down to a fire. And the idea was as soon as it was safe to get that helicopter in the air after a storm had passed, we were out there and we'd contain that fire with a [inaudible] on the ground before it got to a large size.
David: 16:43 So one thing that I think was perhaps immediately, at least perhaps a little bit with the benefit of hindsight apparent from the standing bushfires we've seen is that what, whatever we're doing now isn't really working. Do you see us changing our process? Do you think governments are now paying attention to, well, you know, examining what their current policies are and seeing that they're not really working and then picking a more effective course of action.
Dr Zylstra: 17:19 There's certainly a lot of community recognition of that. A huge amount of recognition of that amongst firefighters and fire managers, whether that will translate into change at a government level is going to be very interesting to see. There's a series of enquiries happening at the moment. And what will come out of those is a, is a huge question for us right now. I know at the federal level there's been a lot of pressure to get the Morrison government to recognise that this is a climate change issue. And to some extent they have recognised that in the Royal Commission they specifically name these fires as having been exacerbated by climate change. And they acknowledge that fires are going to get worse because of climate change. But the irony is that separate to that whole inquiry, they're still working hard to market coal, still working hard to effectively turn up the heat underneath the climate change stove.
David: 18:29 Carry over credits as well?
Dr Zylstra: 18:31 Yes. All of all of this sort of tricky economics. You know, we've got an economy that is largely built on warming that climate and an inquiry looking at one of the effects of the warming asking you know, how do we mitigate the effects of the warming? And in a sense, it's another way of externalising the costs of our fossil fuel industry because one of the costs is these bushfires. And so taxpayers are now being asked to pay that cost and homeowners who lose their homes and people who get sick as a result of the smoke in town, and the smoke, it's not just a discomfort, it's a lethal thing for many people.
Dr Zylstra: 19:25 People who are living with that sort of reality are paying the cost of our increasing fossil fuel use. So the concern is that the government will respond and use climate change as a way of actually I suppose triggering a part of the population that just wants to see us in fear, respond more, with more of the same, more of what we've done before. And so you get this rising call after every fire, we need to burn more. And the more we do it, the less we're seeing it have any positive effect. And it's a bit of a cycle.
David: 20:12 If you could pull one policy lever or push a button or wave a magic wand or what have you, what would be the one thing that we should be doing to prevent these catastrophic fires from taking place? Particularly given that we know that they're going to be getting worse?
Dr Zylstra: 20:29 I would say stop burning old forests to start with. They are our fire advantage. The long unburnt areas that we haven't yet gotten to, and there's not many of them left, they're gold, we need to protect them.So if there was only one thing we could do, that would be good.
David: 20:56 You mentioned that there was a difference between how First Nations people, how Aboriginal Australians were using fire and how the English colonialist forces since used them later. What was that difference and how were they using it differently?
Dr Zylstra: 21:16 So the English approach to using fire was as a tool to change the landscape to make it suitable to English farming and English land management practices. We wanted the landscape that we've got now. Largely, it's clear and it's open and you can put sheep and cattle there. Indigenous fire management was such a fundamentally different approach that our first invaders just couldn't get their heads around it because it was an approach where you weren't looking at yourself as the most important in the landscape. You were one of the species sharing this country. So you, as in everything in Indigenous life, you don't take more than you need. You know, there are all sorts of protocols in place if you're going to specific food plants for example, to stop, you're just greedily picking everything off that plant. You know, in my area the Narrogin people would, we'd have all kinds of rituals and ways of conversing with the, you know, the spirit in the particular plant, for example.
Dr Zylstra: 22:31 Or you would have different kinship relationships that would allow some people to take certain foods and not others and all of that controlled things so that a resource wasn't wasted. Fire was just the same. Any time you're lighting fire, you should only be burning an area that you can directly use and that you need the results of that fire. So fires were very, very focused. And that does vary with the landscape. If you've got a large uniform landscape where particularly in a low production kind of an environment, say spinifex country out in the desert or something, you'd be burning larger areas there. It still works out to a very small proportion of the landscape, but you need more area treated because you have different animals turning up in recently burnt spinifex than you've got in older ages.
Dr Zylstra: 23:33 In the Western desert country, you've got I think it's five different ecological classifications for ages of spinifex. And it's based around what species you can expect to find in those areas. So the point is that Aboriginal fire management was highly specific to country and it involved fire that affected only the area that you could make use of. So if you're burning, say an area of grassland to attract kangaroos there's no point burning a thousand hectares because it's no use to you if kangaroos are attracted to somewhere five kilometres away, you want to burn this patch here so they're attracted to these patch. So when you see indigenous fire management, it's a lot of fires, but they're all very small, lots of little spots across the landscape.
Dr Zylstra: 24:38 And the overall broad landscape has a generally a long unburnt sort of matrix behind it all, where the plants have self-thinned, so they're burning all these little patches in a large area of long unburnt country. And that's how you get a mixture of ages in a landscape that's less flammable and it's, it's the diametric opposite to what we do.
David: 25:04 And I think we'll leave it there. Thank you very much, Phillip, for coming in and sharing your knowledge.
Dr Zylstra: 25:09 Thank you.
David: 25:10 You've been listening to The Future Of, a podcast powered by Curtin University. If you have any questions about anything we've covered, get in touch by following the links in the show notes. Bye for now.