In the aftermath of the Black Saturday bushfires, Kate Giljohann looked for a better way to protect plants and wildlife in the face of extreme environmental changes.
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‘On February 7, 2009, the bushfires of Black Saturday killed 173 people. In my PhD, I assessed the prescribed burning policy that came out of the royal commission inquiry into Black Saturday, the worst bushfires in Australia’s history.
The panel of experts advising the royal commission told the inquiry that the Victorian Government could get away with burning around 5 per cent of public land annually (recommendation 56).
This target was set according to the tolerances of the vegetation that had burnt in the Black Saturday fires but it was applied to all land across all of Victoria. Grasslands burn very frequently and wet forests burn very infrequently, so this seemed like a coarse policy decision.
Wildfires are a necessary and natural part of our landscape. Prescribed burning is one way in which governments can manage and reduce the risk of wildfires to people but it needs to be done carefully.
There are minimum and maximum intervals you want to have between fires.
If your plant is too young to have produced any seeds and a fire comes along, then it won’t regrow afterward. Similarly, if fires are too far apart and the seed store that the plant is carrying dies out, then the plant dies and it’s seeds die.
Prescribed burning in densely-populated areas is difficult, too; the potential impact on human life is severe. So the government burnt a greater percentage of land in remote areas such as the Mallee.
They were meeting their targets but they weren’t achieving their aim, which was to reduce the risk to human life.
The Mallee, which was the region where I completed my fieldwork, is unique in that when a fire occurs it wipes out everything above ground. A typical Mallee eucalypt will then pop back up with multiple stems.
I wanted to gain a landscape-wide understanding of how the animals in this region responded to fire and the kinds of habitat they needed in their landscape. To do this, I used field survey data collected by a number of other researchers over a five-year period.
The surveys looked at recently burnt to long-unburnt vegetation (for example, 100 years since the last fire). I could then use this data to understand at what age (and at what mix of ages) the vegetation was going to provide the most suitable habitat across the landscape.
This was useful but it didn’t help park managers decide how much land they needed to burn in order to maintain a suitable habitat into the future.
To analyse this, I used a mathematical modelling approach to simulate landscape changes over time, such as vegetation growth and the chance of a bushfire occurring.
The model identifies what action a manager should take; that is, whether they should fight a bushfire, light prescribed fires or do nothing to promote a suitable habitat. The decision depends on the current mix of vegetation ages.
A park manager can use this model to assess their own landscape and how animals are likely to respond to changes.
For a species like the mallee fowl, which likes really long vegetation, we can ask, do we have that in our landscape? And if not, how do we go about getting that in our landscape? What would we need to do to achieve this while taking into account unplanned fires?
In the case of the mallee fowl, which like lots of long unburnt vegetation, then that one’s quite simple — don’t burn anything at all. But the mallee emu-wren likes its vegetation a little younger, around 30-50 years old, so you do have to burn something.
How much you do burn would depend on what your landscape currently looks like.
The Victorian Government has since reassessed its target-based policy and adopted a risk-reduction approach. I’m continuing to work with the government to help them with this.
The state has been divided into seven bushfire risk landscapes and prescribed burning is done in high-risk areas around human settlements.
The government’s first aim, above all else, is to protect human life. But there is a second aim, which is to ensure our ecosystems are healthy and functioning.
That’s why monitoring how plants and animals respond to fire is important. We also need to improve our ecosystems’ ability to bounce back from fires.
This has a flow-on effect to our catchments and their ability to collect potable water. We also need a functioning ecosystem in order to store carbon.
These are the basic services of a functioning ecosystem needed to sustain life.’
► Kate Giljohann’s thesis is titled: ‘Optimal fire management for biodiversity conservation.’
* My PhD is an irregular series in which The Citizen speaks with recent Melbourne University PhD graduates.