I wasn’t going to write a bushfire post this year  because I thought there was no need, not with the devastating fires in NSW and QLD to focus everyone’s thoughts. But I’ve just been on Twitter and seen some of the misconceptions about bushfires.
So…here are some basics:
Fire needs just two things to burn: fuel and oxygen. However the size of that fire depends on many things:
- Dry fuel – makes a fire burn harder and faster. Fuel is made of up dry grass, leaves, small twigs and fallen branches that build up on the ground over time.
- Low humidity – i.e. moisture in the air and soil – makes a fire burn harder and faster.
- Strong winds – provide the oxygen to make a fire burn harder and faster. They also transport embers ahead of the main fire.
- Embers – land on dry fuel and start spot fires.
- Spot fires act like pre-ignition for the main fire.
So far, these conditions could apply to any fire, in any country of the world. In Australia though, things are a little different. As well as all of the above, we also have to contend with native vegetation that evolved with fire. Some native plants developed ways to keep the species going after a fire. In fact, the seeds of many of our natives need fire to germinate.
In a nutshell, most Australian natives evolved to burn. This includes gum trees [eucalypts].
- Gum leaves contain eucalyptus oils.
- When these oils heat up enough, they turn into a volatile gas.
- Add a spark and this gas goes ‘boom’. It’s an accelerant – like throwing petrol onto a camp fire.
- Lightning strikes from ‘dry storms’ provide the spark that starts hundreds of fires every year.
So let’s look at a couple of what-ifs. Let’s say a lightning strike starts a fire. If the humidity is high and the fuel is wet – e.g. winter – the fire doesn’t go very far.
But this is what happens in summer:
- Lightning [or human stupidity via an angle grinder creating a spark, an over-heated car starting to burn, a camp-fire left unattended, blah blah blah] starts a fire in grassland.
- The grass fire spreads into scrub land.
- The scrub land fire spreads into native forest.
- The scrub at the base of the gum trees burns hotter and hotter.
- The eucalyptus oil in the gum leaves heats up.
- The volatile oil in the gum leaves becomes a gas and suddenly the whole tree is on fire.
- As more and more trees burn, and the wind pushes the embers and superheated air ahead of it, the conditions for a ‘crown fire’ emerge.
A crown fire is when the fire jumps from tree top to tree top. This is a fire that nothing can stop – no amount of water bombers, no amount of fire fighters, no amount of chemical retardants. In fact, water bombers can’t even get near this kind of fire because it creates its own weather, crazy weather that makes flying virtually impossible.
In 2009, south eastern Australia was in the grip of the Millenium drought and an El Nino weather event. For those who don’t know, during an El Nino period, south eastern Australia goes through an extended ‘dry’ spell with much less rain than normal.
In February 2009, an extended heatwave of 40+ degree temperatures, extremely low humidity, high fuel loads and a ferocious north wind [bringing even more heat from the Centre] combined to create Black Saturday, the worst bushfire event in modern Australian history. 173 people died.
Now, ten short years later, NSW is likely to have another perfect storm of fire conditions…tomorrow…at the very beginning of summer…with the worst of the fire season still to come.
I’ll be honest, I’m scared. Conditions here in Victoria are cool and wet, for now, but the worst is yet to come. How will Warrandyte fare once the grass browns off and the damp fuel load turns into dry kindling? And even if we squeak through this fire season, what about next year and the one after that?
Some years ago I attend a Climate Change rally in Melbourne, and one of the speakers [from the CFA*] said something I’ll never forget. He said words to the effect that there are no climate change deniers at the end of a fire hose.
Climate Change is not causing bushfires, it’s making them bigger and more frequent. Exactly as the climate scientists predict.
Climate Change is also extending the length of the fire season. When I was a kid, January and February were the bad months. In years to come, fire season may extend from the beginning of Spring [September] through to the end of Autumn [May].
Three people have died in NSW already. How many more have to die before we stop ‘praying’ and start doing something useful?
I hope with all my heart that the legacy of Black Saturday means that Victorians remember how helpless we all felt, and act accordingly. We’ve been there. We know. The only thing we can control, even a little, is the fuel load. Reducing the fuel load won’t stop a fire from starting, and it won’t stop a fire from spreading, but it may reduce the severity of that fire by stopping it from becoming a crown fire. Harm reduction. The life it saves could be your own.
And Warrandyte? If you haven’t cleared your block yet, what the effing hell are you waiting for? NSW and QLD may be the canaries in the coal mine this year, but make no mistake, we’re in that bloody coal mine too.
To EllaD and the GO in Taylors Arms – stay safe.
*CFA – Country Fire Authority, the volunteer fire fighting organisation in Victoria.