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Fuel Loads Not Climate Change Are Making Bushfires More Severe

Posted By Joanne Nova On In Fire,Global Warming | Comments Disabled

The Age in Melbourne said they were “keen” to get a piece like this from David on Tuesday, but on Wednesday decided not to go with it.

Unfortunately figures on fuel loads are rare. David used to do carbon accounting for the Australian Government, which included developing the ability to estimate forest debris in Australian forests from a combination of plant models, satellite data on vegetation, and weather data. That capability exists in the Department of Environment, in the unit that produces Australia’s carbon accounts. However the figures here are only what David has heard from other sources over the years, and do not reflect any official or government figures. – Jo

UPDATE: Skynews tells us Defence admit starting the mega Lithgow fire last Wednesday. “A massive fire burning in Lithgow and the Blue Mountains was caused by explosives training which was being carried out in the area by the department of defence.”

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Fuel Loads Not Climate Change Are Making Bushfires More Severe

Dr David Evans

The bibles of mainstream climate change are the Assessment Reports issued by the Intergovernmental Panel on Climate Change (IPCC) every six years or so. The latest was issued recently, in September 2013. Significantly, it backs away from the link between climate change and specific extreme weather events.

The IPCC says that connections of warming to extreme weather have not been found. “There is medium evidence and high agreement that long-term trends in normalized losses [that is, adjusted for exposure and wealth of the increasing populations] have not been attributed to natural or anthropogenic climate change.” The IPCC claim only to have “low confidence” in their ability to project “changes in frequency and duration of megadroughts.”

The official report does say that “drought, coupled with extreme heat and low humidity, can increase the risk of wildfire”, but there is no drought in southeast Australia at the moment.

They also say “there is evidence that future climate change could lead to increases in the occurrence of wildfires because of changes in fuel availability, readiness of the fuel to burn and ignition sources.” Carbon dioxide is a potent plant fertilizer. According to NASA satellites there is more living plant matter today, with a 6% increase in the twenty years to 2000. So there is more to burn.

Some academic papers conclude that climate change might be a contributing factor (Cai, Nicholls), others say it is not (Crompton, Pielke).

If there was any specific evidence that linked climate change to bushfires or extreme weather events, we know they would be trumpeting it loudly. That they don’t, speaks volumes.

There has been a hiatus in the rise of average global air temperatures for the last fifteen years or more. Basically the world hasn’t warmed for the last decade and a half. While this does not rule out warming in some regions, climate cannot have been much of a contributor to the worsening bushfire situation over the last fifteen years.

People have been burning off to keep fuel loads low in Australia for thousands of years.

Current fuel loads are now typically 30 tonnes per hectare in the forests of southeast Australia, compared to maybe 8 tonnes per hectare in the recent and ancient pasts. So fires burn hotter and longer. (The figures are hard to obtain, which is scandalous considering their central importance. There is also confusion over whether to include all material dropped by the trees, or just the material less than 6mm thick–it is mainly the finer material that contributes to the flame front.)

The old advice to either fight or flee when a bushfire approached, and to defend property, only made sense when fuel loads were light. The fire wasn’t too hot, it was over in a few minutes, and we could survive. With the high fuel loads of today, fighting the fire is too dangerous in most cases.

Eucalypts love fire, because it gives them an advantage over competing tree species. Eucalypts regenerate very quickly after a fire, much faster than other trees, so periodic fires ensure the dominance of eucalypts in the forest. Eucalypts have evolved to encourage fires, dropping copious amounts of easily flammable litter. Stringy bark trees are the worst, dangling flammable strings of bark that catch alight and detach from the tree to spread the fire a kilometer or two downwind.

Picture lighting a fire in an outside fireplace. The more newspaper and twigs you pack in, the hotter and faster the fire will burn. Extra heat ignites thicker denser wood, which fuels the fire for so much longer. Now imagine being an ant living in or around that fireplace, and wondering whether to fight or flee. The forests of southeast Australia are our fireplace, and the eucalypts are piling up the easily flammable material around us.

Bill Gammage wrote an excellent book, The Biggest Estate on Earth: How Aborigines made Australia, which was awarded the Prime Minister’s Prize for Australian History and the Victorian Premier’s Literary Award in 2012. The first Europeans in Australia noted over and over that Australia looked like a country estate in England, like a park with open woodlands, extensive grassy patches, and abundant wildlife. Where Europeans prevented aborigines from tending their land it became overgrown, and the inevitable fires became dangerous and uncontrollable.

Particularly memorable is the account of driving a horse and carriage from Hobart to Launceston in the early 1800’s, before there were any roads, simply by driving along the grassy park underneath the tree canopies. Try doing that today.

People will die and property losses will be high until we relearn these lessons and reduce fuel loads again.

 

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