Tuesday, August 3, 2010

Step away from the matches: The Australian bush does not need our help to burn

Can I just head off any immediate abuse by stating straight up: "I am NOT racist!"
Such a claim is usually a sure sign that the person in question is, exactly that. But for most evolutionary biologists, the idea that 'race' even exists as some form of heritable discrete genetic quantity is absurd and disproven (http://www.ncbi.nlm.nih.gov/pubmed/18246066?dopt=Abstract), however, I am going to risk wading into muddy waters when I suggest that culture is not only differentiable, but it is also subject to misinformation and misinterpretation. Not an unpopular statement *yet*, but we'll get to that, in a roundabout sort of way.

To warm up, just as genetic material mutates and is passed on warts and all, subject to selection, so culture changes over time (see 'memes' as genes). Usually this is perfectly natural evolution of human knowledge, perception and interaction. However when we decide that some element of culture should be reinstated to some ideal reconstructed from history, or preserved as a golden moment, then we have problems (consider the Amish, or other religious returns to the dark ages). Think trying to reverse-engineer humans because we think having a tail again would be really cool, or was how evolution 'intended us to be.'
How many problems would that cause? Set aside having to radically rethink the design of chairs and putting a rear hole in all our trousers, the possible side effects that trying to reintroduce such developmental throwbacks might have on the rest of our body are probably prohibitive.
Furthermore, we don't even know whether our ancestors DID have a tail, or at least what sort of tail it was. Should we just try to whack in the best we can come up with and hope it fits? What if the resulting developmental confusion as our little tailed foetus' try to developed is lethal and they don't survive? It's just not a viable, or logical idea, and trying to reconstruct and recreate the past is hard enough, let alone when you have no particularly good idea as to how the past looked.

So how does this relate to, fire, culture, and why am I declaring my racial neutrality?
For many years now it has been the accepted party-line that Australia's landscape has been significantly shaped by the influence of the original Aboriginal inhabitants, particularly through their use of fire. It was cultural.
The argument has been that regular burning as part of Aboriginal custodial tradition has allowed a balance between old growth vegetation and more ephemeral herb fields and grassland. This has allowed the evolution and propagation of fire dependent species, and this in turn delivered us a landscape in utopian balance that we (European invaders) have since unhinged.
While I have no disillusion as to the deplorably negative impact European settlement has had on Australia's natural history, I would reject that the previous custodians had somehow nurtured the continent to some perfect and eternally stable state that depended upon their intervention.

This flies in the face of many studies that have used comparisons of regularly burnt ('managed' - traditional), and 'unmanaged' vegetation to demonstrate (supposedly negative) changes in plant composition over time.
There is a fundamental flaw in extrapolating anything about 'natural' states from such data: you need to know what natural state you are trying to achieve.
So what is this state? Firstly, there is probably no one natural state. Environments are dynamic, and floristics are often in various states of transition on top of and around these influences. Aiming for permanent eucalypt dominated woodland, open heath, or meadow for a sustained period in any one area may well be a false objective.
Secondly, our knowledge of what IS 'natural' is extraordinarily poor. We have no oral, pictorial, or even decent written records of what much of the continent has been like over the last 200 years, let alone for the 40-60,000 years of aboriginal habitation before that or the millions of years of un-humanised evolution before that. Fossils and charcoal records give some indication of vegetation and fire dynamics, but they are coarse and give little indication of the extent, exact timing or cause of the events, or what habitat it occurred in.
Thus we are left trying to freeze in time the state of the environment for the point at which we (somewhat arbitrarily) first started to realize it responded (negatively) to land-use (20th century), flavoured with a little anecdotal tradition from the indigenous culture. This is where I remind the reader about my opening sentence: I am not a racist, and momentarily depart from science based evidence, and resort to personal observation and interpretation.
Recent travel in the Top End and Kakadu brought me, and several other botanists, face to face with the 'traditional burning' allowed in these areas.
From what we could see, this entitles rangers/land custodians to light fires when and where they feel the 'urge.' I will not comment on how far removed this urge is from any wisdom passed on down generations, as I honestly don't know, although I suspect any direct cultural link has probably been well broken by systematic breakup of Aboriginal societies. This appears to result in free reign for a select group to light fires at will, with semi-pyromaniacal abandon. We observed recently lit fires burning vegetation that was no more than a year since it's last burning, with little vegetation showing signs of having not been burnt within the last couple of seasons. Fires were lit from vehicles in convenience to accessible roads, along large fronts, with no apparent regard to previous burning or vegetation type and presumably from similar easy-access points each time.
It was not until we traveled through privately owned and unburnt land that we saw (what we perceived as) more natural vegetation. That is, structured. Including a diversity of upper, middle and lower story species, flowering and fruiting individuals, species that were entirely absent in the 'managed' National Parks, immediately adjacent.
Our conclusion is that 'traditionally managed' land, may in fact be mis-managed.
But as noted above, such observations, and comparison to some 'natural state' are based up knowing what that state is, and is poorly determined by comparing various treatments of different patches (all this tells you is that yes, different treatments lead to different communities, not which of these is most representative of a natural state).

But what support do we have for feeling that fire regimes are over-done, that could not be inferred from comparing-burnt-unburnt-patches and the declared self important role of land custodians? Again, how do we determine what natural state we are trying to achieve?

Well, increasingly, we are able to use evolutionary data. A growing number of unrelated studies, many using the relatively recent innovation of molecular data and analysis, are piecing together the evolutionary history, composition and change over time of Australia's flora and fauna. And increasingly it appears that the ecological adaptations and evolutionary histories of various Australian plants to fire far pre-date anthropogenic (human mediated) activities.
For example a recent study suggests that mallee eucalypts have evolved a number of adaptations (such as epicormic shoots, lignotubers) to arid, fire-prone conditions around 60 million years ago (http://www.nature.com/ncomms/journal/v2/n2/full/ncomms1191.html). Examination of fossil leaf structures also indicate dry and fire-prone habitats well outdate human impact on the continent. While there are some implicit assumptions in these models and estimates that I shall address in a later post, it seems not unlikely that the Australian flora was dealing with natural fire regimens long before human habitation.
So, human impact on the landscape is an extremely recent event in evolutionary terms, with Aboriginal habitation at the oldest, 60,000 years before present thus (1) fire adaptations in Australian species evolved long before the arrival of Aboriginal people, with (2) the majority of adaptation of native vegetation being to natural climatic cycles of aridification, not anthropogenic interference and (3) there are numerous habitats that have evolved in situations where 'natural' burning would not have occurred, but are now ever more burnt out of existence by 'traditional burning' that does not take into account topology, climate etc. Eg, rainforests and vine-thickets of the tropical monsoon are extremely fire prone, must have evolved and persisted in the absence of any significant and recurring burning, despite growing immediately adjacent to fire prone habitat. Now these areas are habitually burnt as there is no consideration that they may not have been burnt in the past.

Australia has had a long and complicated history of natural cycles in climate and landscape that have shaped it's flora and fauna over millions of years. Human intervention is a tiny blip in that story, and the 'natural' (indigenous, human mediated) management state that many propose is just as un-natural as any other human-centric management. Worse, we may be forcing an entirely false scenario of burning onto the environment in an attempt to 'return' to some native state.
We need to realise that
1. no humans are the center of a 'natural' environment
2. we cannot begin to pretend that we can reconstruct a culture that has been so badly disrupted that it can no longer interact with the environment in a traditional manner
3. Australia's animal and plant communities evolved, distributed and interacted long before humans set foot on the continent
3. our environment has shaped the culture in it, not the other way around.

Let natural fires be, and understand that our fires be not natural.

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