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Bushfire research in the Mallee

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Matt Smith:

Hello and welcome to the La Trobe University Podcast. I would be your host Matt Smith and joining me today is Associate Professor Mike Clarke, Head of the La Trobe University Department of Zoology. Thank you for joining me Mike.

Mike Clarke:

Pleasure.

Matt Smith:

Now you're here today to tell me about the Mallee Fire and Biodiversity Project which you have been working on for a few years now and you're the head of that project along with Professor Andrew Bennett from the Deakin School of Life and Environmental Sciences.

Mike Clarke:

That's right.

Matt Smith:

So can you tell me first about the Mallee? What is the Mallee?

Mike Clarke:

The Mallee is a region of inland Australia that is characterized by a tree type. It's a type of eucalyptus, which has multiple stems rather than a single trunk and that tree type extends across a lot of Southern Australia but we've been studying it in the area around Mildura and a region called the Murray Mallee.

Matt Smith:

Parts of Northern Victoria and Southern New South Wales is it about that sort of area?

Mike Clarke:

Yeah that northwest corner of Victoria and New South Wales and does they have Australia, yep.

Matt Smith:

What sort of size are we talking here?

Mike Clarke:

It's a big area, with an area three times the size of Belgium if that means anything but it's extensive.

Matt Smith:

And what sort of trees and wildlife do you get here? What sort of environment is it?

Mike Clarke:

It's a semi-arid environment with a unique set of flora and fauna. A number of threatened species live in this part of the world so it's a fascinating area to work in and it's critically important because so many spaces in that area are on the brink of extinction.

Matt Smith:

And what sort of work have you been doing there? It's to do with fire control isn't it?

Mike Clarke:

It's looking at the response of fauna in particular, to fire. In the past most of fire ecology has focused on how plants respond to fire and the assumption has been made if the plants are kept happy and in the landscape then animals will follow suit and will also be accommodated. We're interested to test that idea.

Matt Smith:

And now what is control burning and why is it done? How does it work?

Mike Clarke:

Control burning or plan burning or prescribed burning, they're all the same thing. Their primary role in most landscapes is to protect human life and property and we strongly support the use of prescribed burning. There is also a use of prescribed burning for ecological reasons to maintain certain age classes of vegetation that the flora or fauna need.

So it can be used for different reasons but it's primary purpose in most of Australia has been used to protect human life and property and reduce the risk to human assets in times of extreme fire weather.

Matt Smith:

The idea here is also that it frees up the access to sunlight a bit and gives younger plants sort of a bit of a chance to grow through doesn't it?

Mike Clarke:

It does. There's a whole group of plants and ecosystems in Australia that have evolved with fire. The critical issue is how often? How frequent is the fire? How large it is and how intense it is? There's a sort of a simplistic view across much of Australia where we quickly say well fire's a natural component of the Australian ecosystem, which is true but the critical issue is the devil's in the detail. How big? How often? How intense?

The attempt is always made to keep it under control but it's an imprecise science. We're dealing with the vagaries of weather and the fuels, their combination and the managers do the best they can to burn in a way that he's under control but sometimes it gets out of control.

Matt Smith:

It's generally seen as being a broadly beneficial thing to the environment. But you said that you've been studying the effects on fauna, which haven't been widely examined, so what have you been finding?

Mike Clarke:

A range of responses. We've been looking at 840 sites across the Mallee and a whole range of different kinds of animals. So we've worked our way up from termites and scorpions and bugs on leaves to reptiles, mammals, birds, and we see different responses from different groups of animals but some similarities between them. So some are at their highest peak soon after the fire and then they declined but don't disappear from the landscape whereas others only exist in some of the really long unburnt areas of the Mallee. Some of the classic iconic fauna of mallee like the malleefowl, which people are familiar with the, has a mound nest. These are more predominant in the really old age classes where there's thick litter layers, which they use to build their composting nest. And so they need large extensive areas of old Mallee in which to survive.

Matt Smith:

Now I assume that also with that you just get the general problem of displacement of homes as well?

Mike Clarke:

That's correct. If you're an animal and the resources you need be it a big clump of spikey spinifex in which to breed or a hollow in a tree in which to breed. If the fire consumes that, you won't be able to colonize that site again until that resource is back in that landscape. And that's been one of the most interesting aspects of our studies, how long it takes for some of those key resources to return after fire? The hollows for example, hollows in which a budgerigar might nest. You're talking about a time span of at least 40 to 50 years before hollows begin to develop in those trace. Let alone be big enough for a budgie or for uhm, a cockatoo.

So these are really long time periods and prior to our study, there wasn't appreciation of how long these processes took. The plants could respond after the fire and be as happy as Larry and flaring and sending seed, the mallee eucalypt within nine to ten years. And that's beautiful for the plant it can replace itself but for a pygmy possum or a bat that needs a hollow to nest in, it's got a 50 to 60-year wait before the hollows start to appear in that landscape.

So the frequency or the intervals at which we put far back into that landscape are critically important for the survival of some clay fauna.

Matt Smith:

You could selectively from this point in theory burn parts of the Mallee so that you don't encourage some species to inhabit it and that would maybe have a bearing on, say, introduce pests because I'm sure there's plenty of those in the mallee.

Mike Clarke:

There are introduced pests but they weren't the focus of our study but you're right in your first premise that how we go about introducing fire or keeping fire out of the mallee will have profound effect on the composition of animals that can persist in that landscape.

Matt Smith:

How is the mallee? Have you got sections of it that are really old? Can you tell?

Mike Clarke:

One of the most exciting aspects of our study was developing a new method of aging mallee. Prior to our study, the only way you could map how old the mallee was was using satellite imagery, which only started in 1972. And you would compare photographs and therefore you could work out when certain areas were burned based on that satellite imagery.

We have developed a method of aging mallee based on the growth rates of mallee following fire that now allows us to estimate the age of a mallee based on the diameter of the stems. And we've got sites out there that are at least 160 years since they have been burned. And that's really changed their view of how often fire occurs in these landscapes. There are lots of sites across the mallee that have escaped fire after over a century. And it's those sites that have the resources that are critical to some of these hollow dependent fauna.

Matt Smith:

What sort of environment changes do you get between a site that's old and a site that's been burned within the last few years?

Mike Clarke:

At the oldest sites you will get larger mallee trees so four to five meters in height. They will have limbs that will have hollows in them. They'll have a lot more bark and litter underneath them but there'll be much more spaced further apart. So that was a surprise as well to us that as the mallee gets older, the gaps between the trees get bigger and therefore the continuity of fuels can actually decrease. Whereas some people feel when a certain site hasn't been burned for many decades it must be getting worse and worse and more and more risky in terms of fire risk.

In some cases, many of the fuels actually decline over time in the absence of fire as the trees get further apart. And so the chance of the fire spread through it. Those older landscapes become less rather more.

Matt Smith:

So after all these years of doing the study, do you think that fire is a good thing or not to an environment like the mallee?

Mike Clarke:

It's an essential part of the mallee ecosystem. That's what the fauna have evolved to cope with but as I mentioned earlier the devil's in the detail and what we have done in our study is start to shed some light on the precision of how often fire needs to occur in this landscape prior to our study this wasn't known as clearly.

Matt Smith:

For how long has there been controlled burning in the mallee? Does it go back to Aboriginal times?

Mike Clarke:

It's really unclear the extent to which aboriginals would've burnt the mallee. Most of the fires currently occurring by lightning strikes. They can be large extensive fires under extreme weather conditions that seems to have been historic pattern. It's really unclear in this region the degree to which the aboriginal population moved into the mallee. The concentrations of population seemed to have been along the Murray. The mallee area was a fairly inhospitable place, very little surface water and it's not clear why they would spend large amounts of time in the mallee nor why they would burn it.

Matt Smith:

And how about modern times, how often is it burned? And how much of it is burned?

Mike Clarke:

That's currently under review. In the last 35 years, we have calculated that about 1.1% of the mallee burns each year and recent recommendations are for that to be increased dramatically.

Matt Smith:

That would be on bearing of the fires that happened in Victoria a couple of years ago that wouldn't it?

Mike Clarke:

Following the Black Saturday fall as the bushfire's rule commission has come out with a recommendation that statewide there'll be a target of 5% of annual burning of public land. That would be four times the historical average as we have studied it over the last 35 years.

Matt Smith:

Your research, has had any bearing on it or do you think that that is maybe excessive? That amount?

Mike Clarke:

When we look at the response of fauna and the resources they require, we're worried that that level of burning would do harm and do very little to reduce the risk to private property and assets.

Matt Smith:

How much of the fauna is directly affected by this? Lots of large scale fauna that people know about but how the stuff that lives in the leaf litter?

Mike Clarke:

There is but we haven't studied the leaf litter invertebrates. There are groups of organisms that really are very resilient to fire. So the scorpions and the termites that are really important components of the ground fauna of the mallee live in burrows, they tolerate fire quite happily. They go down their burrows, they come up. The world has changed after the fire but they seem to cope because they have these refuges underground. So different kinds of fauna respond quite differently to fire and a significant proportion of the mallee fauna is quite resilient to fire.

Matt Smith:

Is there any areas of the mallee that are kind of out of bounds for the fire burning? I assume that there would endangered species that you don't want to disturb.

Mike Clarke:

There are a number now that we have highlighted, require particular resources and these are typically the ones that require extensive areas of long unburnt mallee. Things like mallee emu wren, blackeared myna, malleefowl, and we've developed a mapping technique now where we can identify where those exist and that's probably one of the most valuable products out of this research project is using satellite imagery we can now identify and recognize remotely where the really old growth exist. And that's valuable information for land managers because they then know how to protect rare age classes in the mallee.

Matt Smith:

I seem to remember that when land sectioned off to trying to control burning like we're going to burn this area here but we've also got to leave a wildlife corridor as well. Tell me about wildlife corridors and how they work in the mallee?

Mike Clarke:

Yeah, it's a basic landscape ecology that you need connectivity in the landscape so that if a resource becomes unavailable in one area, animals can move to other areas where that resource exists and when the resource resumes or recovers in the burnt area they can come back in.

And that's one of the profound challenges that the managers face across the mallee, is ensuring there is connectivity and reducing the risk of a whole reserve being burnt in one hit. And we've studied part of that in south Australia or there's a reserve called Billiat reserve and over 85% of that reserve got burned in one fire event in the 1980s. That makes a massive impact on the fauna because your sources of recolonization are very limited when that much of it's burned. And Billiat is an isolated reserve. It sits out on it's own in the middle of cleared wheat paddocks. So the chances of wheat dispersing animals re-colonizing that site are very, very slim.

Matt Smith:

How big does a corridor have to be for it to constitute a corridor? I mean I know it's different for different animals. I think the koalas got a very bizarrely narrow corridor but generally how do you have to leave?

Mike Clarke:

You're quite right. It differs profoundly between organisms and some of them are really puzzling as to how reluctant they are to cross barriers. You can get a bird like a white-browed treecreeper that will be reluctant to even cross wheat paddocks to get another patch of bilar habitat. And either bird of the same size will happily fly to Siberia and back every year. But this white-browed treecreeper, whatever it is in the evolution of history they do not like crossing gaps. So the individual differences might frustrate and we don't understand them but that's what we meant to be managing for and accommodating.

Matt Smith:

You just finished a big long-term four-year project, what were the main findings that you took out of this? And where do you take them from here?

Mike Clarke:

I think the key findings that we're most interested in is the slow pace at which resources recover after fire, for a number of species of animals that we need to reexamine how we think the landscape recovers after fire and not just focus on plants. We have to consider the needs of animals and the needs of animals recover much more slowly. That's I think the most fundamental finding of this project. And because we develop this technique of aging mallee, we now know we're talking about recovery taking over century caused fire. So that's basically finding that even should be a major consideration as we take on the responsibility as a society to manage these natural areas and introduce fire while also protecting human life and property.

Matt Smith:

What is the next step in your research?

Mike Clarke:

We're also undertaking other far research in different parts of the state of Victoria. I've got long-term research taking place at Wilson's Promontory looking at the recovery of the bird communities after fire down there. We have a large project in a king like Murrindindi fire complex where we're looking at the value of unburnt refugees after the big fire goes through. We're really interested to examine the value of prescribed burning in that landscape now that it's been tested by the big fire did it create the refugees that we believe it creates? And if the unburnt areas exist, do the animals agree that they are great refugees that we have for them?

So it's really going to the heart of the ecological value of prescribed burning for the fauna and flora. And we're also just about to start another study in the Box Ironbark region around Rushworth. Again looking at the impact of prescribed burning and its value for fauna.

Matt Smith:

That's all the time we've got for the La Trobe University Podcast today. If you have any questions, comments or feedback about this podcast or any other, you can send us an email at podcast@latrobe.adu.au. Mike Clarke, thank you for your time today.

Mike Clarke:

Thank you.