Episode #25
E24: The Myth of Fuel Reduction - with Associate Professor Phil Zylstra
Many years ago, I began noticing some serious impacts on bushland following planned burns, or fuel-reduction burns. I was seeing the loss of old trees, destruction of rare and threatened plants, loss of habitat, and impacts on native fauna. But over time, something else became even more concerning. These burns were being carried out with the aim of reducing fuel loads, yet in many places I was seeing the opposite. Burning was stimulating dense recruitment of shrubs and other fire-responsive pioneer species, and changing the structure and condition of the vegetation. In some places, within a few years of being burnt, the vegetation seemed denser and potentially more flammable than it had been before the burn. I've done quite a lot of work in this space myself, and I won't go into all of that here. But if you're interested, I gave a talk for the Victorian Forest Alliance looking at some of these issues, which you can view here: https://www.victorianforestalliance.org.au/recording_karl_just_webinar When I started digging more deeply into the science behind what I was observing, one researcher whose work really stood out to me was Associate Professor Phil Zylstra. Phil is a fire ecologist and fire-behaviour scientist, but importantly, he didn't come to fire purely from an academic background. Before and during the early years of his research career, he worked in fire management and as a remote-area firefighter in the Snowy Mountains. So his understanding of fire comes from both working with it on the ground and studying it scientifically. Over many years, Phil has investigated some really fundamental questions about how fire actually behaves in Australian forests and how vegetation changes following fire. He's developed sophisticated fire-behaviour models that look beyond simply how much fuel is present, to consider things like the species involved, plant traits, vegetation structure and how those characteristics influence whether and how a fire spreads. A major focus of his work has been on what happens to the flammability of forests as they recover from disturbance. His research has challenged the relatively simple idea that older vegetation necessarily means more fuel and therefore greater fire risk. Instead, his work shows that in some forest ecosystems there can be a period of increased flammability as dense vegetation regenerates after fire, followed by a decline in flammability as the forest matures, plants self-thin and the structure of the vegetation changes. That was particularly fascinating to me because Phil was finding, through detailed and peer-reviewed research, patterns that were very similar to things I'd been observing in the field for years. In the podcast we talk about what actually happens to vegetation following fire, how fuels and flammability change as ecosystems recover, and whether repeatedly burning forests to reduce fuel can sometimes have the unintended consequence of maintaining them in a younger, denser and more flammable state. We also get into some of the broader complexities of fire ecology: the relationship between fire and vegetation, the effects of repeated burning on ecosystems and biodiversity, and what the evidence tells us about how we might manage bushfire risk differently in the future. I also want to give a quick plug for a Eucalypt Identification and Ecology Course that Vicky Shukuroglou will be running, and that I'll be helping to teach. The course runs over four days across October and November 2026, and we'll visit a range of very different ecosystems around Melbourne — from tall, wet mountain forests to much drier woodlands in the west. We'll see a wide diversity of eucalypts, learn how to identify them, and, importantly, explore their ecology and their relationships with the landscapes and ecosystems in which they occur. If you would like to learn more about the course, please visit Vicky's website at: https://eucalyptsmelbourne.au/course/
