Expert Q&A: Bushfire behaviour and management

Dr Philip Zylstra is an Associate Professor at Curtin University and an expert in bushfire behaviour and management.

What are hazard reduction burns?

ZYLSTRA: The idea of it is that as forest is left unburnt, it accumulates fuels over time, and so it needs to be burned to remove some of those fuels and that then stops the next bushfire being as severe.

How effective are they?

ZYLSTRA: There's a very small amount of evidence that they have a very short-term, small effect. So nearly all of the evidence is theoretical. As far as actual measured results, empirical evidence, there's a very small, short-term effect, because you clear the ground. So, a fire can't burn if the ground is completely clear, but that can be very short because you'll often get grass growth coming straight back afterwards and that'll carry the fire. But then following that, you’ll get a long period, often decades, where you've got a significantly increased risk. And so that's the part that's generally not considered in the equation, and they only look at the potential benefit of it and don't necessarily consider the long-term costs.

How do hazard reduction burns increase long-term risks?

ZYLSTRA: There's a general rule in forest ecology that if you have tall plants, and you remove those by some sort of disturbance, that they'll regrow from the ground, which makes a lot of sense. Take out a tree or a large plant, then there's a vacancy, there's some light and water and nutrients available for other plants. And some of the surrounding plants that haven't been taken out, they might use up some of it, but you get a much faster response from other plants growing from the ground.

The idea of hazard reduction is that it tends to treat all biomass as if it's a risk. So, all living plants are treated as if they're part of a hazard. But in reality, say during the Black Summer fires, about 11 or 12 per cent of the time they burned as crown fires. Crown fire is when you've got right to the treetops burning. So the other nearly 90 per cent of the time, the trees weren't burning so the trees weren't fuel. If they're not burning, they're not fuelling the fire, and if they're not fuelling the fire, they're slowing the wind that's underneath them… So the more vegetation you've got in a forest that isn't burning, the slower the fire spreads. And so what happens when you do a prescribed burn is that, yes, you've cleared the ground and you create an advantage for – sometimes it can be a few years, in some seasons, it can just be months – but the scorch from the flame kills a lot of the taller plants that were slowing the wind down and they now regrow from the ground where they're available to burn as fuels because anything that's close to the ground is much more likely to ignite.

Do hazard reduction burns pose a threat to wildlife?

ZYLSTRA: With a prescribed burn, what tends to happen is that you have a block of land surrounded by roads, or sometimes rivers, and you start out by lighting up along all of those roads and rivers – they're called the control lines – and that fire burns inward, and then you'll get aircraft that will drop incendiaries inside the burn block and light up the centre of it. So, what happens is, all of the animals there have nowhere to run to. They're completely surrounded by fire. So, animals that normally survive by running away from the fire can't do that in a prescribed burn situation, even if it's not as severe or intense as a bushfire.

What alternatives are there to hazard reduction burns?

ZYLSTRA: We come from a mentality that we think of ourselves as kind of having to fix things; we have to take charge. And if you if you stand back and look at it a little bit philosophically, we're one of the species that's put its hand up and said, “I’m in charge of everybody else”. So, we've kind of assumed a lot for ourselves. When in reality, forests actually survived with fire for a long, long time before people were here to log them or burn them and save them from themselves. They're actually okay by themselves without us to save them from fire and it's because they have what's called ecological controls, and what I described before about taller plants slowing fire down, that's part of the ecological control system…I suppose it's a twin-pronged kind of an approach…We need to let our forests get old again. We've got to stop disturbing them, because if we don't disturb them, they will eventually become less flammable. And the way we can let them get older is by having enough people trained in things like raft firefighting and resourcing those crews. And, also, I would say not just relying on people volunteering their time anymore. Climate change is having a massive effect, and we can't just rely on the goodness of people's hearts to fight it anymore. We've got to hugely expand the numbers of paid firefighters to get out there.

A lot of people think that burning the bush is something we should do because Aboriginal people did it. And Aboriginal fire use was entirely different to the way we do this… The general rule from the people who I've heard talking about it was that they wouldn't light, and they don't light, a fire that they can't control with a green branch themselves. So, it's an area the size of a house or backyard, something like that, and they might spend a day on that on that area and control it really carefully instead of burning 10,000 hectares at a time like we do today. So, a lot less forest got burnt and was burnt very, very carefully. They would steer it so that it doesn't go into trees, where they knew that, say, ringtail possums were nesting or something important like that. They'd keep it away from important habitat trees or areas, a log where they knew that there were animals nesting in, because they knew all of those details of the landscape and they could apply that level of focus. But what's happened is, we've got a kind of response to it all in Australia – it's actually a little bit racist – where we just think that Aboriginal fire management must have been simple. They used fire and that's all we need to know about it, and so we assume we've got 65,000 years of learning under our belts and whatever we do now must be similar. And so there's a lot of cultural appropriation going on now where governments are trying to market burning the bush as if it's Indigenous management.

Why do authorities seem so resistant to transitioning to alternative strategies?

ZYLSTRA: The evidence is actually overwhelming. There's almost nothing at all supporting prescribed burning as a useful tool, but there's very strong public opinion. And if you have a government that says we're not going to do any more prescribed burning, you have talkback radio and public opinion saying “this is a government that's not going to save us from bushfires”, and people aren't rational.

After the September 11 attack in America, they knew that Iraq had nothing to do with it, but the response was to go and bomb Iraq and people feel like something's being done. So even though it made things worse in the long-term, people felt like they were being cared for. And the same is true here. You've got a political cycle where politicians will probably lose the next election if they don't do a lot of prescribed burning because it's just too hard to convince the public. You've also got huge number of jobs of people who are trained to set the bush on fire and we need to change that. We need to train a lot more people into better firefighting.