Aboriginal Burning Promotes Grassland Biodiversity in Australia’s Desert

We have a new paper out in this week’s Proceedings of the National Academy of Sciences Early Edition.  The paper suggests that subsistence related burning increases local landscape heterogeneity and may promote biodiversity in Australia’s Western Desert.  What’s really interesting about this is that promoting biodiversity is not the goal of individual hunters – they are really just trying to maximize their foraging returns.  My Stanford Anthropology colleagues Rebecca Bliege Bird and Doug Bird have been working with Martu foragers in Western Australia since 2000.  They gather amazingly detailed quantitative ethnographic and ecological data, focusing on such classic problems as understanding subsistence economy in a foraging population and the ecological factors favoring a sexual division of labor.

Martu foragers burn the climax spinifex grass in search of goanna lizards and in so-doing, promote the growth of plant species that cannot compete with adult spinifex, which is a nasty grass with high-silica content:

Spinifex is extremely flammable and once a fire is started in a patch, it will race through until it is pretty much all burned.  The vegetation that characterizes other successional stages is far less flammable.  Previous work by Doug and Rebecca has shown that burning increases hunters’ encounter rates and probability of capturing goanna lizards and other prey species. 

Using their detailed information on hunting and burning, we correlated foraging activity with measures of habitat heterogeneity derived from satellite imagery.  We compared local habitat heterogeneity in areas where Martu were actively foraging (and burning) to areas where there was no foraging and the fire regime was instead driven by lightning ignitions.  What we found was that the heterogeneity in the foraging localities was greater than in the “natural” burn regimes.  In particular, foraged localities had remarkably uniform distributions of successional stage.  The non-foraging localities would show peaks at different successional stages — depending on the age of the last burn — but the frequency of whatever stage was present would typically fall off from whatever the characteristic mean was.  In contrast, the successional stage distribution we observed in the foraged localities looked like a mixture of several different smaller “natural” localities.  This is because that’s essentially what they are!

When people burn for subsistence needs, they tend to start lots of small fires at many different times.  What results is a mosaic of successional stages. But this is really a local re-arrangement.  When we looked at the landscape level, the diversity of habitats looks very much like that of the smaller foraging localities.

One interesting implication of this work is that the human impact on the Australian environment — grassland engineering, if you like — was likely to only be substantial following the establishment of more intensified aboriginal economies (approximately 1500 years ago).

It may seem counter-intuitive that hunting with fire promotes biodiversity, but that really seems to be what is happening here.  The results have clear conservation and management implications. Excessive fire suppression in highly flammable grasslands is probably not a good idea.  Now we need to measure the actual species diversity rather than simply the diversity of habitat types.

See Rebecca’s fire ecology website for more on this research and reprints of various papers.  The full text of our paper can be found here.


13 thoughts on “Aboriginal Burning Promotes Grassland Biodiversity in Australia’s Desert”

  1. Sure we in Australia know that the aboriginals use fire to scare animals to help us trap them. But this is not new nor is it to guess that when there were ore aboriginals there was more fire!

    And to simply overlay some sattelite photos and then confuse yourselves with science speak is utterly irrelevant. The bush fires in Australia raging in Victoria are NOT lit by the Aboriginals who mainly live in remote settlements and in urban squalor and are instead more linked to global climate change than a tribe who happens to be in the pocket of Americal researchers. It may sound scientific to use satellite imagery but it means nothing about the past (when they didnt have satellites) and nothing about the present when other factors other than that tribe catching goannas come into play!

    And for those of us who actually live here in Aus and work with we are far more concerned with the aborignal population who are not some perfect isolated tribe to exploit at a distance but those people who are reeling from the byproducts of the modern age in urban centers. And as for "fire ecology" a ridiculous concept in todays age of CO2, the bush fires in Victoria which are out of control and killing urban population.

  2. In fact, as I read today that 108 people have been killed in the fires, I actually get quite angry with this kind of "research". How on earth does looking at some satellite pictures and some fact that aboriginals set fires to scare animals their way have ANY significance for ecology? It is utterly irrelevant to the problems of today and completely devoid of historical significance because the pictures being studies are contempory! And to dress this up as "ecology" because ecology is academically in vogue, at last, really points to the utter irrelevance of anthropology in a globalized world where no community is isolated, no community is in a petri dish, and even if they were then that communities experience cannot be generalized to any other as all else are utterly interconnected and reeling from the effects of global climate change.

    To preach some confused notion of fire ecology today, as people are being burned and killed by bush fires is an academic farce that I stumbled across in my search for the source of the Victorian bush fires.

  3. Well, Tim, your angry rant not withstanding, I think that the tragic fires currently devastating large tracts of Victoria actually highlight the need for carefully done fire ecology. The recent events in Australia dramatically underscore this as do the enormous wildfires that have beset us here in California and the American West more generally over the past decade. So far, we have not experienced the degree of human tragedy that you are seeing in Victoria, but I fear it is just a matter of time.

    Ecology is the scientific study of the distribution and abundance of life. If human burning affects either the distribution or abundance of plant or animal species -- which it certainly does -- then it is the proper subject for ecological analysis. Furthermore, ignoring human agency in such a case would yield a trivial and incomplete ecology.

    We actually make no claims of relevance to contemporary problems in the paper. We are trying to understand the dynamics of this particular system. That said, I nonetheless think there are findings of policy relevance embodied in this work. Fire needs fuel and the fuel for wildfires is the vegetation in "wild" areas. As you note, there are no parts of the world untouched by human influence either directly or indirectly. By setting many, small, low-intensity fires through their subsistence hunting, the Martu alter the landscape and make it less flammable. In effect, the successional mosaic that arises from this practice creates a landscape of firebreaks. This is precisely what back-country fire-control teams do in battling wildfires. The Martu just do it preemptively.

    How to manage highly flammable landscapes in more densely settled areas like coastal Australia and the American West is an enormous problem and I don't claim to have the answers. However, ideas informed by landscape ecology are clearly part of the solution. Engineering human-dominated landscapes with greater structural heterogeneity seems essential for dealing with this emerging chronic problem of arid temperate and sub-tropical climates.

    If you read the paper, you would see that the remotely sensed imagery was directly linked to on-the-ground observations of hunting bouts. The RS imagery therefore has direct bearing to the behavior of specific contemporary human populations.

  4. Thank you Jamie for you're insightful, comprehensive, and timely response to Tim's rant. Might I just add one thing: Tim, what you think you know incorrect and disturbing. You would be wise to read the paper before commenting on it.

  5. We in land management are NOT against burning off. It is an important part of our job and they should of done more of it in Victoria.
    What I am "ranting" against is confused eco speak of the type which may have in fact contributed to the type of poor land management that created these fires.

    Sure the Abos light fires to get their kangaroos to jump in one direction. This is not news. But you seem to be telling me that they burn off so that they can manage the land in a better "fire ecology". This is so silly its a joke. They are nomads. They dont and didnt care about owning the land. They only care about where their food is coming from. The fires ONLY helped them to get food, not to diversify the plants or even to enrich the soil. That that happened because of their fires is not news nor is it anything to do with the Aboriginals intentions. They were and are not farmers. They dont even like living in one place let alone looking after the land.

    Burning off is burning off. It is something people do around the world to stop the spread of fires. The enemy here is not burning off but confused pseudo science that pretends that burning off is something more significant than it is. Its exactly that kind of pseudo ecology that led to people not cutting back the trees around their houses, or allowing the bush undergrowth to get too dense and that is why it makes me "rant." For all I know the arsonists were not lighting fires but doing some idiotic attempt at "fire ecology". Playing with fire is dangerous unless you know what you are doing.

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