Explainer: What Really Causes Australian Bushfires?

Image: Getty Images

As Australia's bushfire crisis continues, more people are seeking to understand how these bushfires were started, and why they've spread so far. Unfortunately, in our quest to understand 'why', many people have been quick to throw accusations. But what really causes bushfires?

Australian politician Barnaby Joyce and various TV personalities have blamed a lack of hazard reduction for our current bushfire crisis. Many others are blaming arsonists, while American far-right conspiracy theorist Alex Jones reckons it's all a government ploy to prioritise light rail developments. On social media, even ISIS has been posited as a culprit.

According to Australian Government entity, Geoscience Australia, the spread of bushfires, while common, is extremely complex, and can't be limited to just one factor.

How do bushfires start?

Bushfires are a natural result of the hot, dry conditions of Australia's environment, particularly over summer. Importantly, they're also a normal part of Australia's ecosystem, with several native plants relying on them to regenerate and grow.

While arson can be a factor in bushfire ignition, statistics from last August charting the causes of bushfires over a year-long period identified only 1.3 per cent of recorded fires being linked directly to arson.

More commonly, fires are ignited by legal or illegal burn off that may run wild, lightning storms and electrical faults - with lightning accounting for "about half of all ignitions in Australia." Many others are started accidentally by human fault, such as via campfire embers. But while their ignition points are important to understand, it's the study of their spread that is most vital.

How To Help Australian Bushfire Victims

As of Monday morning, ongoing bushfires have continued to devastate Australia. At least 24 people have died, many are missing, and roughly 4.9 million hectares and one thousand homes have been destroyed in New South Wales, one of the hardest-hit states. The fires have also ravaged the lands of national parks and impacted the air quality of major cities like Sydney. Here's what you can do to help.

Read more

How do bushfires spread?

Image: Getty

Several factors determine the spread of bushfires, and they're part of the reason why Australia's bushfire season has lasted so long. These include the amount of fuel and oxygen present in the environment, but spread is driven by a variety of factors.

Available fuel: This is the volume of bark, leaf litter and other natural dry material that is consumed by the fire as fuel. Think about when you're lighting a campfire or bonfire - the smallest leaves burn the quickest, adding to the height and strength of flames. The same is true for bushfires, with the presence of small litter encouraging a longer lasting fire.

Temperature and dryness: Hot, dry fuel easily ignites, while damp or wet fuel won't. This is why Australia's fire season is far more damaging in summer, when rain is scarce. Fires are also encouraged by hotter temperatures, because fuel will naturally be closer to its burning point, making ignition easy.

Wind speed: Stronger winds bring more fuel into the path of fires, allowing them to grow bigger and spread. Winds are also able to create new fires via the transference of embers, which then ignite other patches around the original fire. This process is known as 'spotting' and can happen up to 30km away from a fire.

Humidity: Plants become easily flammable at lower humidities because they lack the moisture to combat the heat.

Slope angle: Fires operate on a convention and radiation basis, meaning that bushfires travelling uphill will spread faster than they do travelling downhill. Steepness is a factor in this, and may aid fire advancement.

It's important to note that while all of these factors play a part in the ignition and spread of fires, they are aided by the rise of climate change, which has led to the drier, hotter conditions where bushfires thrive. Understanding this, and how they're spread, is essential to identifying the key causes behind Australia's current crisis.

Five 'Climate Change' Myths You Need To Stop Believing

Misinformation and lies are regularly used to undermine the science of climate change – here's how to see through the fog.

Read more


Comments

    But the root cause is lack of trees. No trees = no rain.

    Who removed the trees from every piece of flat land there is ? A few current Australian billionairs made their money clearing the land to feed foreign countries.

    These same billiaonairs should pay for every house, and every animal lost. Some have started to just that; see SMH today under WA billionaires Andrew and Nicola Forrest have announced a $70 million donation.

      I find your theory quite bizarre considering that our forest very thick and full of very flammable eucalyptus trees, are the ones that are on fire and creating the inferno that we are experiencing. We have thousands and thousands of hectares of bushland that is protected not just in public land but in private property. We have laws that even ban landowners from clearing land.

      Are you sure that you are not getting mixed up with what was happening in Brazil, where the president is encouraging the clearings and lighting of fires?

      The root cause is the warming of the planet plus mismanagement of the available fuel during the "safe months" like the very wise Aboriginal communities used to do and done for hundreds, probably thousands of years. That should be given back to them, they are the ones that know how to do and what to look for to do it.

      Australia's temperatures have risen faster and higher than anywhere else in the world. It was always a very dry continent with a fringe of thick forest/bush on the coastal regions, mainly on the East of the continent and, although true that when the white people invaded the first thing they did (apart from massacres) was to mas clear many areas for agriculture and there was and still is a stand of with the logging industry (and yes, I have witness the impact of logging) there is and has been in place many laws that prevent private land clearing and they are working on a sustainable logging that is being introduced and enforced, albeit a fair bit too slow for many of us.

      Last edited 09/01/20 2:42 pm

        We can all marvel at our remaining 2% lush forests, we can all think a lousy 2% is plenty, but it is nothing like the 20% odd before Europeans came. Take a drive along the Stuart Highway, once out of the parks; 100% cattle and zero trees.

        Or maybe ask the indigenous elders of N QLD, they will tell you of the rains before the land was cleared. However, if readers think trees have nothing to do with rain, then so be it.

          I am pretty sure that I did address what you say in your reply. But that was a very long time ago. I have been, as I said, to may places 3 decades ago that had been "murdered" and then I went to those same places within the last 5 years and the reforestation, mainly by volunteer groups and by enforced plantation by very disgruntled loggers that thought they could get away with not doing it, was nothing short of miraculous.

          The warming of the planet and the disruption on the climates (rain where there was hardly any to the point of constant severe flooding) and drought in others that used to get a good amount of rain amongst many other changes is actually born much higher in the gases of the atmosphere and is made worse by the deforestation of the whole world.

          The biggest "jobs" of trees are 2;

          1) produce oxygen and absorb the carbon dioxide in the air and store it in their tissue. If you chop down trees then there are less to absorb and store one of the biggest gasses that are causing global warming. Those stored gases are released again into the atmosphere when the tree trunks and branches are burnt as well. All plants with leaves can and do photosynthesis through them, but trees are the best at it and at absorbing and storing carbon dioxide.

          2) They help to stabilize the soil and absorb excess water and that stops torrential rain from forming torrents that wash the topsoil away and also minimises and even stop mudslides, as the roots form a complex structure that holds the soil, especially deep down, in place.

          Trees don't produce rain or water. If they did that, our bushland in all those places where is so thick that firefighters can't access the original fires to extinguish them before they take hold and become infernos wouldn't have such an explosive and dire fire ability.

          There is severe mismanagement of bushland. That should've been left to the local Aboriginal tribes in each area to keep on looking after like they have done so knowledgeably, wisely and efficiently for thousands of years.

          Australia was 1.52 C higher than the 110 years average last year. Here is the recent article from BoM that shows it and THEY KNOW AS IT IS THEIR JOB TO KEEP THOSE RECORDS:

          https://www.9news.com.au/national/100-years-of-temperatures-bushfires-normal--bom/6fade093-124e-4c08-b8e4-91c36c416e17

          Deforestation all around the world is criminal, to say the least, but trees ARE NOT responsible for the creation/production of rain. They are, however, a very intrinsic and extremely important cog in the engine of keeping the planet (and all us, plants and animals) healthy and balanced. When that is achieved and all the pieces of the puzzle are in the right place, then the extremes of dryness/wetness/crazy extreme (and becoming more and more common) weather events will also stabilize.

          Rain is created by the number of bodies of water, humidity in the air and in the soil evaporating and rising to encounter colder upper layers in the atmosphere which condenses that vapour and eventually falls back to Earth as rain. As the air layers warm-up, the vapour has to travel higher and higher and the strong wind currents in the upper layers have more time to disperse/take somewhere else where it is colder to turn it back into water droplets.

          That causes the original places where the vapour started to dry up more and more as it loses humidity, including the trees on those areas, and the bodies of water to diminish and eventually dry up altogether, causing the droughts that we have been experiencing and, thus, creating the perfect conditions for these fires to, not only start and take hold, but to turn into the infernos that we are experiencing more and more often.

          And then you also get the idiots who believe that the law, like fire bans and the such, do not apply to them that greatly contributed to this as well as natural causes like so many of the dry thunderstorms that we had been experiencing and, again, the problem with bad land management and badly kept electricity lines and many very volatile chemical products not stored correctly.

          Deforestation IS a problem, A HUGE PROBLEM, and we are shooting ourselves on the foot by doing it, but, right now, what is burning and spreading the firest and making them so bad that they are creating their own infernal localized weather ARE DENSELY PACKED TREES. Which we are losing so many of and we can't afford to lose any of!!!!

          Last edited 10/01/20 11:45 pm

          I am pretty sure that I did address what you say in your reply. But that was a very long time ago. I have been, as I said, to may places 3 decades ago that had been "murdered" and then I went to those same places within the last 5 years and the reforestation, mainly by volunteer groups and by enforced plantation by very disgruntled loggers that thought they could get away with not doing it, was nothing short of miraculous.

          The warming of the planet and the disruption on the climates (rain where there was hardly any to the point of constant severe flooding) and drought in others that used to get a good amount of rain amongst many other changes is actually born much higher in the gases of the atmosphere and is made worse by the deforestation of the whole world.

          The biggest "jobs" of trees are 2;

          1) produce oxygen and absorb the carbon dioxide in the air and store it in their tissue. If you chop down trees then there are less to absorb and store one of the biggest gasses that are causing global warming. Those stored gases are released again into the atmosphere when the tree trunks and branches are burnt as well. All plants with leaves can and do photosynthesis through them, but trees are the best at it and at absorbing and storing carbon dioxide.

          2) They help to stabilize the soil and absorb excess water and that stops torrential rain from forming torrents that wash the topsoil away and also minimises and even stop mudslides, as the roots form a complex structure that holds the soil, especially deep down, in place.

          Trees don't produce rain or water. If they did that, our bushland in all those places where is so thick that firefighters can't access the original fires to extinguish them before they take hold and become infernos wouldn't have such an explosive and dire fire ability.

          There is severe mismanagement of bushland. That should've been left to the local Aboriginal tribes in each area to keep on looking after like they have done so knowledgeably, wisely and efficiently for thousands of years.

          Australia was 1.52 C higher than the 110 years average last year. Here is the recent article from BoM that shows it and THEY KNOW AS IT IS THEIR JOB TO KEEP THOSE RECORDS:

          https://www.9news.com.au/national/100-years-of-temperatures-bushfires-normal--bom/6fade093-124e-4c08-b8e4-91c36c416e17

          Deforestation all around the world is criminal, to say the least, but trees ARE NOT responsible for the creation/production of rain. They are, however, a very intrinsic and extremely important cog in the engine of keeping the planet (and all us, plants and animals) healthy and balanced. When that is achieved and all the pieces of the puzzle are in the right place, then the extremes of dryness/wetness/crazy extreme (and becoming more and more common) weather events will also stabilize.

          Rain is created by the number of bodies of water, humidity in the air and in the soil evaporating and rising to encounter colder upper layers in the atmosphere which condenses that vapour and eventually falls back to Earth as rain. As the air layers warm-up, the vapour has to travel higher and higher and the strong wind currents in the upper layers have more time to disperse/take somewhere else where it is colder to turn it back into water droplets.

          That causes the original places where the vapour started to dry up more and more as it loses humidity, including the trees on those areas, and the bodies of water to diminish and eventually dry up altogether, causing the droughts that we have been experiencing and, thus, creating the perfect conditions for these fires to, not only start and take hold, but to turn into the infernos that we are experiencing more and more often.

          And then you also get the idiots who believe that the law, like fire bans and the such, do not apply to them that greatly contributed to this as well as natural causes like so many of the dry thunderstorms that we had been experiencing and, again, the problem with bad land management and badly kept electricity lines and many very volatile chemical products not stored correctly.

          Deforestation IS a problem, A HUGE PROBLEM, and we are shooting ourselves on the foot by doing it, but, right now, what is burning and spreading the firest and making them so bad that they are creating their own infernal localized weather ARE DENSELY PACKED TREES. Which we are losing so many of and we can't afford to lose any of!!!!

    Funny you said because, no trees = no fire too.
    Lack of fire breaks, several kilometres of them to accommodate for eucalyptus is needed.

      If there were no trees there would be no fires - absolutely correct. However, the world is bigger than that.

      Perhaps trees 1000's klms away were the trees creating rain clouds to rain on our nearby dry forests ?

        Once again. TREES DON'T CREATE RAIN. TO SAY SO DEMONSTRATES A VERY POOR, EVEN INEXCISTENT UNDERSTANDING OF HOW RAIN COMES TO BE.

        Rain is created by moisture in the grown/bodies of water, warmed by the sun and being evaporated. The vapour rises from the ground/body of water and travels upward until it meets up with colder gases that condensate the moisture and form clouds. As the clouds find colder and colder temperature, they become heavy and fall to Earth as rain. As the planet heats up because of climate change, the clouds have to go higher and higher to find colder air to condense it, they also are more exposed to stronger current on those higher altitudes and they will travel further and further before they are condensed and heavy enough to fall as rain. Thus creating more and more areas of bad drought and high temperatures for longer and in wider areas.

        The reason why these bushfires are so bad is the very dryness of the areas, INCLUDING THE TREES AND BUSHLAND. There is no moisture to slow them down. everything is too dry INCLUDING THE TREES AND THEIR BRANCHES. Add that to the fact that Eucalyptuses and Malelaucas (our most common native trees) are very volatile as they are rich in flammable oils and that higher regions and many commercial plantations are rich in pines, also a very volatile species, and you have a recipe for disaster.

        No tree will "create" water out of nowhere. No tree will "create" rain. Trees have only as much moisture/water as the amount present in the environment where they live. In a drought, that is extremely little and thus why we have the present bushfire crisis.

        Of course, if they wouldn't be murdering so many trees and deforesting large surfaces of the land, then the trees would be able to keep more moisture in the ground, as one of their purposes is to stabilize and protect the soil from the heat of the sun.......

        BUT DEFINITELY THEY DON'T "CREATE WATER OF RAIN" OUT OF THIN AIR!!!!!

    No boycott beef and dairy? Australia is a major producer and exporter of this commodity for centuries, and livestocks emit disastrous amount of GHG and methane -- the greenhouse effect that makes our planet hot and dry

Join the discussion!

Trending Stories Right Now