Fuel reduction, a contrary view

Every official enquiry into the causes of Australia's big bushfires has concluded that more off-season preventive burns are needed to prevent a recurrence of such fires.  Greenies worldwide however have a long history of obstructing such burns.

The far-Left ""New Matilda" has found a couple of scientists who defend the Greenie actions. They say that preventive burns are ineffective.  I excerpt their argument below.  They say that most preventive burns just consume the ground cover, leaving the tops of the trees intact.  And the tops of the trees are plenty to support a big bushfire.

So what do they conclude from that?  They conclude that we are always going to have big bushfires so we had better get used to it.

That is however a very strange conclusion. It is both a non sequitur and a counsel of despair.

If what they say is generally true, I would have thought the obvious conclusion to be that preventive burns have to be more thorough.  If wildfires burn the tops of the trees then preventive burns have to do that too.  Obviously, the bigger the preventive burn the riskier it is going to be but big efforts at containment should be possible.

A two-step procedure may be needed.  First burn off the ground  cover then attack the top cover.  That would surely halve the risk.

But it is all theory.  In most locations getting any sort of preventive burn done seems to be near impossible.  The inertia of the State government fire authorities seems set to ensure that we will continue to have big fires for many years to come.

Dr Byron Lamont a Distinguished Professor Emeritus in Plant Ecology with Curtin University, and Adjunct Research Fellow Dr Tianhua He explain:

The knee-jerk response to the devastating wildfires that have raged in Australia this summer has been for some to demand a more intensive program of prescribed/controlled burning before summer begins. But what are they and do they even work?

Prescribed burns are fires created by fire management authorities to reduce fuel in an attempt to stop the advance of future possible wildfires.

Unfortunately, areas that recently received a prescribed burn have offered little resistance to the advance of current wildfires. The fires have just passed straight through them. But why?

Current practices of prescribed fires essentially burn the ground flora, the shrubs, herbs, and creepers. At most, heat from the ground might scorch the upper canopy, and they tend to be patchy. These are called surface fires.

But wildfires burn everything. They create their own inferno.

Their greatest heat is produced from fuel in the tree canopy. The convective currents created by the firestorm spray embers up to kilometres from the fire front – they simply drop onto or over areas that have received prescribed burns.

These are called crown fires.

The aim of fire managers is to avoid crown fires during prescribed burning for fear that the fire gets out of control and will go far beyond the area intended to be burnt.

Controlled fires are only meant to stop the odd cigarette thrown out of a car window from starting a fire, or lightning strikes igniting the ground flora. They may not even achieve those goals, because scorching the trees above can lead to considerable leaf drop and build-up of litter that increases flammability and deters germination and seedling establishment.

Nature conservation was never one of its overt goals, though research by these same fire management authorities claims that no harm is done. And because they always fall behind in their prescribed burning program, independent ecologists are usually satisfied that species diversity does not appear to be harmed.

The only effective deterrent is areas that have recently experienced a wildfire, as no combustible fuel remains. This inhibitory effect might last for five or so years when the vegetation can carry a fire again.

Ironically, the Australian flora has experienced wildfires of the current type for many millions of years.

It is adapted to wildfires, not prescribed burns.

Thus all eucalypts, paperbarks, she-oaks, and banksias release their seeds only when their canopies are burnt and there is massive seedling recruitment in the next wet season that ensures the vegetation recovers.

Ultimately, we are guests in the world’s most flammable continent and have to learn to live with that fact. The Aboriginal inhabitants learned to but we have not.


No comments:

Post a Comment

All comments containing Chinese characters will not be published as I do not understand them