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Sunday, 14 May 2017

Control burning

This is something I wrote first in 1994, but this weekend, the air of Sydney is heavy with the smoke of control burns: we have had a number of lush years, and the standing fuel loads are high.

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I got up early one Sunday to drive my older son down to the ferry wharf.  We live on the top of a hill, and as we pulled out of the drive-way, the hills to the north were almost hidden in smoke, each ridge more hazed than the one before.  Angus suggested that there would probably be more smoke haze before the day was out.  The trees on our hilltop were motionless, and so I had to agree with him.  We have had several mild and calm days, and the control burners have been out in force, getting ready for the coming summer.

These people have a simple aim: reduce the fuel levels close to any natural or artificial barrier that might slow the progress of a fire.  Get rid of the dead fuel on the ground, they say, and you can stop a fire anywhere.  Roads and fire trails often travel along ridges, and these can be used to stop fires dead, provided the available fuel has been burnt before the fire comes through.

A wildfire feeds on the gases that explode out of the fuel as the first searing blast leaps forward.  The drier the fuel, and the more finely divided it is, the more gas it produces in the first moments, and the worse the fire becomes.  If the fine, dry, standing fuel is burnt out before then, the summer wildfires will be starved.  That is why we burn the bush each year in winter and spring.

Aborigines "using fire to hunt kangaroos" by Joseph Lycett: like many early
white visitors, Lycett failed to understand the science involved.
Our natural environment has been regularly burnt, perhaps for the last 50 000 years, so our plants and animals are adapted to that sort of regime.  The original owners burned the Australian bush, clearing the undergrowth.  This helped them find the best track from A to B, it improved hunting, and it brought on new growth for prey animals to feed on.  So every living Australian plant is long since adapted to recovery from burning, the rest are long dead.  Equally, the bush animals which exist today are those which are well-equipped to escape from fire.

If we burn different patches in different years, we get the whole of a bush area running through a mosaic of stages.  In this way, nearby unburnt areas can first supply a refuge for the animals, and then later be a reservoir of seeds and immigrants to repopulate the burnt areas after the fire.  These small fires are slow, low in heat, and give wildlife a chance to escape to neighbouring areas.

Some people say that ‘conservationists’ oppose the practice.  This committed conservationist does not oppose it, because control burning kills feral plants and weeds, limits the spread of feral animals, and maintains the biodiversity of an area.  It is far less harmful than a rampaging wildfire every twenty years.  The opponents are mostly people who let emotion get in the way of good sense.

The most effective method is to make regular burns along roads and ridge fire trails, making a site for a fire break in time of need.  Of course, the cowboys who give 4WD off-road vehicles a bad name are forever demanding more roads and better access into wilderness areas, as though letting hoons in will somehow stop the fires from happening.  We need the fire trails, we need the fire breaks in moderation, but we don't need any more hoons in the bush.  The fire trails must be securely locked off, and we have to steer a middle ground between the mad green disease and organised ruthless perpetual arson.

Control burning must be carried out with care, whether it is the mosaic form or the roadside form.  Personally, I favour regular roadside burns to eliminate the weeds which grow there: cars are a major transport method for weed seeds.  This has been proven by analysing (would you believe it?) the sludge tanks of car wash establishments!  A good fire every year or two, penetrating five or ten metres from the road's edge, will see off most weeds, for they are unused to regular fire, and unable to penetrate beyond the disturbed roadside verges in any case.

One Sunday afternoon, in spring, 1994, we visited a favourite bush area, one that was badly burned in then previous January.  It is on a ridge fire trail with a large area of waratahs on its north side, which should have been blooming by then.  Waratahs have large spectacular red flowering heads, rather like the related Protea, and well worth the walk.  As we walked, my son and I played our usual spring ‘spot the species’ game, while my wife, a better taxonomist, pointed out all the ones we had missed.

Running across the photo, you can see the fire trail we walked in on.
Duncan and I found thirty species in flower before we got to the waratah patch.  All the way along, the southern side of the track showed unmistakeable scars from January's fires, even now, while the northern side seemed almost to be unmarked.  The fire fighters had clearly burnt off the southern side to make a fire break, and we started to gather hope for ‘our’ precious waratahs.  But just before the waratah patch, the wildfire had jumped the track, and the whole site was burned out.  We found maybe fifty young waratah plants, and many of the larger plants had survived, and were suckering nicely from the blackened trunks.  There would
be no flowers in 1994, and only a few next year, but 1996 should easily make up for it.

The fire had only run a small distance beyond the waratah patch: far enough to do significant short-term damage to the patch, but also far enough to ensure that there will be waratahs there for many years to come, sprouting from the ashes of their predecessors.

We climbed to the top of the next hill and looked at the plumes of white smoke rising all around us.  I wondered how many other waratah patches were being licked into shape, somewhere inside those burning areas.