Proceedings of the 1994 symposium on biodiversity and fire in North Australia -
Biodiversity series, Paper no. 3
Deborah Bird Rose (editor)
Department of the Environment, Sport and Territories and the North Australia Research Unit, The Australian National University, 1995
Fire in the desert: Increasing biodiversity in the short term, decreasing it in the long term
Conservation Commission of the NT, Alice Springs
I hate machines, like this slide projector. I'd much rather be out in the bush showing you what's going on.
Peter Stanton and I met halfway between Queensland and the Northern Territory and when we first met we thought we were both quite mad! Because everything he said was the exact opposite of what I said; but, in fact, now we've known each other for quite a while we realise that what goes on in Queensland is almost the mirror image of what happens in the Northern Territory. Everything is opposite.
I guess it all boils down to grass. I mean, that's the only thing the desert and the Top End has got in common, and grass is bloody important when you're talking about fire.
I grew up at Hermannsburg. As a kid I was brought up by Arrernte women and I had Arrernte playmates and I learnt about fire. Fifty years I can say I've been lighting spinifex, so I'm a bit ahead of you Peter! And I had the world's best pyromaniacs to teach me. The unfortunate thing for the Arrernte people is that in the desert, short-grass is very precious! Short-grass in central Australia is very sweet and you can grow very fat cattle quickly. It's short, but it's sweet.
Aborigines learnt quickly that if you burn short-grass, pastoralists get very upset. So, they thought they could use that to get rid of the pastoralists but they quickly learnt differently. Natural selection took over because what happened is they got shot. So, any of the good Arrernte burners were shot out of existence and so there's really no good Arrernte burners left. Natural selection has taken care of that.
So overall, we have too much grass in central Australia and it's mainly a very beautiful plant, spinifex. The amazing thing, believe it or not, is that it can live on the smell of an oily rag. It can grow out of boulders. And that's how it survives. It beats everything else by somehow managing to live practically off fresh air. Unlike the Sorghum up here, in the Top End, it doesn't go away. It accumulates. Even termites will only eat it when it's about fifteen years old. So, even though we don't get much rain you can get fifteen years worth of growth and fifteen years worth of fuel before it starts reducing. This is very different to the Sorghum situation. So, spinifex doesn't go away.
As I said, it hangs around. There's nothing will eat it except a little ant, although it doesn't eat it directly. The ant uses the sticky substance from the spinifex to cement sand grains together and make cowsheds. There's little sucking insects in here which are sucking the sap out of the spinifex and the ants feed off that sap. So, this is the only animal I know that lives entirely on spinifex. But there is one thing that will eat spinifex. The thing that'll eat it is ... fire. You can say that spinifex is dependent on fire for its very existence.
Now, I'll go through this photo sequence here. Here you can see recently burnt spinifex, straight after the fire – bare ground (Plate1). The spinifex is totally gone. Here it is, six months later after we've had a good rain on it (Plate2). Now, the important thing is there are lots of annual plants present. I'll talk about them in a second.
Two years later we end up with this situation where the spinifex is coming back in. You can see that the earlier plants are dying out (Plate3).
And at eight years you're back to spinifex again and you can see that's ready to burn again (Plate4). Just how soon it's ready to burn again will depend entirely on rainfall. It's got nothing to do with time. In the desert you cannot predict when you're going to have to burn. It's got nothing to do with time. It's got everything to do with rainfall because you can have thirty inches in one year or you can have thirty inches over ten years.
Okay, now, the Aborigines were well aware of this and they burnt the spinifex in such a way that they produced this fire-weed – desert raisin. Through firestick farming they managed things like this Solanum. This is the same family as the potato or the tomato. Bloody good tucker! And it comes up by the acre after a fire so that you can wander around here and collect this stuff very easily. The beauty about it too is that in the desert the fruit doesn't rot. You can come back a year later and that nice, dried fruit is still hanging on the bush. Okay? So, there is no doubt at all that Aborigines burnt spinifex to produce these wonderful gardens because not only do you get food but you get this thing here pituri (Nicotiana) – the native tobacco which gives you stimulation as well. One of the main reasons for burning a lot of the country was to produce drugs!Yeah. It's a fireweed, pituri. You can trade anything with this, anything you like. It's even more valuable than grass in central Australia.
So, the Aborigines had a very good system. About a third of their food, I would say, came from this system of managing the land. Yes. So, they used firestick farming to produce this mosaic of country at different ages. On this photo you can see that this area down here has been burnt about a year ago (Plate5). The area behind hasn't been burnt for quite a while. This recent patchy one was lit by Aborigines creating their garden, right. So, after the next rain you'll have new growth in this recently burnt area. You'll have two year old tucker back in here. Way back in the distance you can see some dark stuff here, some mulga, which is fire sensitive, it didn't get burnt and it produces a whole range of different foods. So, you end up with this lovely mosaic, giving you lots of different tucker.
The trouble is, as I said before, spinifex doesn't go away and you can get, as we have in the Tanami desert right now, ten years of accumulation of spinifex. We're talking about atomic bomb energy! Sitting there ticking away. Tick, tick, tick. Some of these fires are so big they have created their own cloud. When CSIRO were doing experimental fires, they managed to produce a hail storm out of a clear sky just using one match!
So, fire in spinifex can be very dangerous when it intrudes into other communities. In the hills, for example, the fires can be so hot that the rock will just explode, it's called exfoliation. You can tell where the hot fires were in the past just by looking at the rocks. The worst thing about a severe fire is that it bares the ground and after a hot summer fire you're likely to get a heavy rain afterward and the soil just washes away. Of course, soil is the most important thing for plants, and this is where the fire has its effect! It's not killing the plants. We all know that every plant that lives in Australia, except in the wettest parts near Cairns, has to be fire tolerant to survive because Australia is the driest, or second driest continent on this planet. When you lose your soil, you're in trouble and that's the main effect that fire has in central Australia and that's where the long-term changes occur.
After a big fire on the spinifex sand-plain country you'll get sand blowing all over the place. If you don't get rain for years afterwards that sand will eventually form into sand dunes! But the spinifex doesn't care, it is superbly adapted to fire. Just the same as your eucalypt grassland up here is. No problem with it.
But it's the fire sensitive species like mulga that die, unlike the mallee, which regenerates beautifully from the base. So, even though in spinifex country we increase our biodiversity by this burning system, we are losing fire sensitive communities when the fire expands out of the spinifex into communities like this rare Acacia (Acacia ammobia) that grows near Ayers Rock (Plate6). As you can see, this Acacia is happily growing on the sand dune crests and there's nice thick mulga down here in between the dunes. Lovely, thick vegetated country for a desert. We are looking at low rainfall country.
Another rare Acacia grows in the hills. Acacia undoolyana occupies only a few square kilometres of the desert. In the photo (Plate7) you can see where a fire came through, came racing up the hill here, took away all but these few trees. You can see the dead stumps poking up here everywhere else. Regeneration is happening but the spinifex has got in and affected another rare plant that grows here – it's got a great name this one – Ricinocarpus gloria-media! Well, I'm afraid it's glory is short lived because it's on the way out. This plant is now extinct in that area in the photo. It's gone. The spinifex has just got rid of it.
But it's not just the plants that are suffering! Now, in central Australia we've had the world's greatest extinction of mammals. Nowhere else on this planet have more mammals disappeared. And we are talking about one of the biggest areas of wilderness left on the planet. Two-fifths to three-fifths
In central Australia the brush-tailed possum is incredibly rare. Simpson's Gap, one of our national parks, is one place where the possum is found. The spinifex is lurking, just waiting to come in (Plate8). You could call the area where the possum lives a bit of desert ‘jungle'. You can see that there is a big mixture of plant species living here. It is a beautiful diverse bit of country! And, of course, if you're a possum, you've got a hell of a lot more choice of food here than you have in the spinifex. I don't think you need too many neurons to work that out. And, of course, that spinifex will destroy this given half a chance.
We have now burnt a firebreak to stop the spinifex taking over and to keep the possum safe.
So, what are we doing to stop spinifex taking over? We've got rangers who love burning spinifex, spinifex can be burnt quite easily, much more easily than the vegetation in Queensland. (Except for the heath, of course.) And what we're doing produces a situation where you've got a fire sensitive community protected by just burning firebreaks all around to keep the spinifex out.
Okay, what about traditional Aboriginal burning? Well, we can learn a hell of a lot. They are out burning the Tanami desert now. They know what they're on about. The trouble with watching Aborigines is that an expert makes things look easy You know, to watch an Aboriginal burning, he does it in such a way it looks as if he's just throwing matches around. But we've heard earlier on about how you've got to know what you're on about. It's like watching a butcher! You watch a good butcher boning out meat, the meat just falls off the bone! But it's only years and years of experience that make it look easy. And it's the same thing with burning the country.
The only trouble is, as mentioned earlier, once your burning system has been stopped it is one hell of a job getting it back again! This is what Peter and other people have talked about. An area in the Mann Ranges in South Australia has now had three fires through it. This last one was lit by Aborigines but they didn't realise the problems that occur when the fuel had built up. They had been away from their country in the past and the system had broken down, so this hill got burnt three times in 20 years. A whole lot of figs, which are sacred in this country, were burnt out of existence and the rock wallaby which is practically extinct on this range, has lost some of its tucker.
The other problem, of course, is we've got all these bloody introduced animals in central Australia. The rabbit has taken over a huge amount of country. You see the burrows in this photo (Plate9), the rabbits didn't dig these burrows! These were dug by a rat kangaroo. Rabbits are actually not really good diggers. These underground houses were made, ready-made for the rabbits, by this beautiful little marsupial and as the Aboriginals said to me, 'The rabbits came along and said – 'can we share your house?' and the marsupials being good generous Australians said – 'yeah, you know, help yourself'. But the trouble is, rabbits are greedy and they took over – took over the whole lot.
Now, the worst thing is not only have they extincted this poor little rat kangaroo that initially made this warren. They are now fluctuating out of control. In many places where a bad fire went through and killed the mulga, plenty of young mulga came up afterwards. Okay? And Aborigines are used to that. They know that if a patch of mulga gets burnt just make sure it doesn't get burnt again during the next ten years. No worries, it'll come back. But the rabbits came along and they actually ringbarked the young seedlings. It's something to do with sharpening their teeth. Even when there's a tonne of tucker around they still kill woody seedlings. I think they just don't like shrub country. They like open country. So, the rabbits have completely stopped any regeneration.
And, of course, cows, well we all know that cows have changed things. And, of course the problem too is fences in central Australia. If Aboriginals want to do traditional burning on cattle country wooden fences will burn down. You've gotta have steel fences, don't you? But see, cattle, in fact, are causing the opposite to what happens with rabbits. Because they take away all the grass you rarely have any fires now. Because there's no grass left. And what we're ending up with is shown in this photo (Plate10). I grew up here, this is my country. That's the Finke River, the oldest river in the world. I used to be able to stand on the bank here and look right up to the hills ten miles away. Look at it now. It's thicker than most of the bloody country you've got up here in the Top End with five times our rainfall! And this is because this hasn't been burnt for a hundred and ten years. The first missionaries that came up here said, twenty years after they had been into the country, they said – 'The country is now getting thicker because the cattle are eating away the grass and Aboriginal fires are no longer occurring.'
We've not only got introduced animals but we've also got introduced plants. There is buffel grass, another bloody invasion. This perennial grass is great for cattle but it produces twice as much fuel as the native species it's replaced. The river red gums which are the biggest and the most important trees in central Australia, many animals use them for nests and for shelter, buffel grass is now killing the tree. The native grasses would have only produced about half the fire intensity and the tree would have survived that fire. And buffel grass always thickens up after a fire – it loves it.
There has been another big change as well. The Arrernte people, for example, have important sacred sites where lots of Dreamings meet up with each other. These places were like, you know, the biggest, the most wonderful cathedral in Australia. And, of course, they were also the best places for recolonisation. There's a place called Running Waters, the best waterhole in central Australia, which was an absolute sanctuary. The waterhole runs for about four miles. Pelicans breed in it. It is now utterly stuffed! It was the very first place that white people came in and unwittingly put all their cattle. In other words, it's as if the whites came up here, found the cathedral and then went and shat on the altar! And burnt the vestments.
But this system of sanctuaries is now broken down. In the desert you've got to have this system because you have really bad droughts and so on. You've got to have a sanctuary from where your animals can expand back out after a drought. Not a single animal was allowed to be killed in this area. Not a single plant was allowed to be picked. These sanctuaries were scattered all over the landscape – wherever there was important Dreaming there was a sanctuary area.
Now, these are the main reasons why we can't go back entirely to Aboriginal traditional burning. But there's also another important factor. (I suppose you can call me a scientist, but having been brought up by Aborigines I'm probably more of a naturalist.) But there's one thing that scientists are on about! Aborigines are, well in my part of the world anyway, were the world's best natural historians, but the big difference between natural history and science, is that science in a lot of important cases is anti-common sense.
Now, I've got a gun, okay, a high powered rifle, I'm standing on a flat plain, I've got a bullet in one hand and a bullet in the gun and I shoot the gun and I drop the bullet at the same time. Which bullet is going to hit the ground first? They both hit at the same time! I mean, that is anti-common sense. You would think the bullet that is going ten kilometres would take longer to hit the ground. Now, evolution is like that. When you think about it, it doesn't really make a lot of sense. Animals evolve, become successful only if lots of them die. It's called survival of the fittest.
So, a lot of important scientific principles at first don't seem to make a lot of sense. That is the big difference between natural history and science. We were able to get onto the moon because science has made big breakthroughs by teasing out these anti-common sense laws. The only problem with this is that us scientists are so used to dealing with anti-common sense things that when you put most of us into the field we're often not very practical. What we have to do is combine together. Get the world's best naturalists and the worlds best scientists, put 'em together and you've got a winner. Thank you.