A wildfire, wild land fire or rural fire is an uncontrolled fire in an area of combustible vegetation occurring in rural areas. Depending on the type of vegetation present, a wildfire can also be classified more specifically as a brush fire, bushfire (in Australia) Wildfires can be characterized in terms of the cause of ignition, their physical properties, the combustible material present, and the effect of weather on the fire.[1]
Three major natural causes of wildfire ignitions exist:
Bushfires in Australia are a widespread and regular occurrence that has contributed significantly to moulding the nature of the continent over millions of years. Eastern Australia is one of the most fire-prone regions of the world, and its predominant eucalyptus forests have evolved to thrive on the phenomenon of bushfire. The gradual drying of the Australian continent over the last 15 million years has produced an ecology and environment prone to fire and has cause significant property damage and loss of both human and animal life. Bushfires have killed approximately 800 people in Australia since 1851, and billions of animals, In January 2020, it was estimated that over 1.25 billion animals have died in the 2019-2020 Australian bushfire season.[2]
[1] www.sciencedirect.com last viewed on 28-1-2020
[2] Estimated 1.25 billion animals killed in Australian bushfires, TV10, last viewed 28th January 2020
An aerial view of the wildfires.
FACTORS THAT CREATE A BUSHFIRES TO OCCUR.
The basic factors which determine whether a bushfire will occur include the presence of fuel, oxygen and an ignition source. The fire intensity and speed at which a bushfire spreads will depend on ambient temperature, fuel load, fuel moisture, wind speed and slope angle.[1]
Fuel load
Fuel load describes the amount of fallen bark, leaf litter and small branches accumulating in the landscape. Generally speaking, the greater the fuel load, the hotter and more intense the fire. Fuel which is concentrated but loosely compacted will burn faster than heavily compacted or scattered fuel sources. Smaller pieces of fuel such as twigs, leaf litter and branches burn quickly, particularly when they are dry and loosely arranged and will burn quickly in the fire front. Larger fuels, such as tree trunks often burn later after the fire front has passed. The natural oil within eucalypt trees promotes the combustion of fuel.
Fuel moisture
Dry fuel will burn quickly, but damp or wet fuel may not burn at all. As a consequence, the time since rainfall and the amount of rain received is an important consideration in assessing bushfire danger. Often a measure of the drought factor, or moisture deficit, will be used as an indicator of extreme bushfire weather conditions.
Wind speed
Wind acts to drive a fire by blowing the flames into fresh fuel, bringing it to ignition point and providing a continuous supply of oxygen. Wind also promotes the rapid spread of fire by spotting, which is the ignition of new fires by burning embers lofted into the air by wind. Spotting can occur up to 30km downwind from the fire front.
There is a threshold wind speed of around 12 to 15km/h which makes a significant difference in the behaviour of bushfires in the open. When wind speeds are below this threshold, fires with heavy fuel loads burn slowly. However, even a slight increase in wind speed above this threshold results in a significant increase in fire behaviour and advancement. The width of a fire front also has an influence on the rate of spread and a wind shift can immediately widen the forward edge of a fire.
Ambient temperature
The higher the temperature the more likely it is that a fire will start or continue to burn. This is because the fuel is closer to its ignition point at high temperatures and pre-heated fuel loads burn faster.
Relative humidity
Dry air promotes a greater intensity fire than moist air. Plants become more flammable at a low humidity because they release their moisture more easily.
Slope angle
Fires pre-heat their fuel source through radiation and convection. As a result, fires accelerate when travelling uphill and decelerate travelling downhill. The steepness of the slope plays an important role in the rate of fire spread. The speed of a fire front advancing will double with every 10 degree increase in slope, so that on a 20 degree slope, its speed of advance is four times greater than on flat ground.[2]
Ignition Source
Bushfires can originate from both human activity and natural causes with lightning the predominant natural source, accounting for about half of all ignitions in Australia. Fires of human origin currently account for the remainder and are classified as accidental or deliberate. Fires lit deliberately can be the result of arson or might be designed to achieve a beneficial outcome but conditions have changed, resulting in uncontrollable spread.
Unfortunately deliberate and accidentally lit fires are more prevalent near populated areas and have a disproportionately higher risk of infrastructure impact. Arsonists place people and property at serious and unnecessary risk, particularly when igniting fires on extreme fire weather days.
ANALYSIS OF AUSTRALIAN BUSHFIRE 2019
Australia’s unprecedented bushfire season continues to unfold; competing arguments have been made about the principal causes of the human and environmental tragedy particularly around the role of climate change. Past year’s bushfire season is widely regarded as one of the most severe on record since September, fires have spread across much of south eastern Australia following a period of extreme drought and record-breaking temperatures.
By the beginning of 2020, around six million hectares had been burned, mainly in the states of New South Wales and Victoria. The affected area has been described by various publications as roughly twice the size of Belgium, Maryland or Wales, on 7 January, this area had expanded to more than 10 million hectares or “an area the size of South Korea”, according to Reuters.
Dozens of people have been killed by the fires and thousands of buildings have been destroyed. Monitoring agencies reported that the infernos have “cut-off communities, destroyed hundreds of homes and shocked the world with images of holiday-makers forced to shelter on beaches”.
According to, ecologists at the University of Sydney estimate more than one billion birds, reptiles and mammals in New South Wales alone are likely to have died in the rapidly spreading wildfires and tens of thousands of livestock are also likely to have been killed.
After the fires had already burned for around three months, NBC News noted that, despite thousands of fire-fighters battling to contain the blazes, “many continued to burn out of control, threatening to wipe out rural townships and causing almost incalculable damage to property and wildlife”. With more than 100 separate fires burning at once, air quality across the region has also been affected considering to which public-health emergency has been declared.
Factors that turn the Bushfire more devastating.
Extreme heat and dryness are two important influencers of fire and, on both measures, 2019 was remarkable for Australia, Australia experienced its hottest year on record in 2019, with average temperatures 1.52C above the 1961-1990 average. Our second hottest year was 2013, followed by 2005, 2018 and 2017,New South Wales one state hard hit by the bushfires – broke its record by a greater margin, with temperatures 1.95C above average, beating the previous record year, 2018, by 0.27C.
At a very basic level, rising levels of greenhouse gases in the atmosphere change the Earth’s radiation balance, allowing less heat to escape. Australia also had its driest ever year in 2019, with rainfall 40% lower than average, based on records going back to 1900. NSW also had its driest year.
Fire authorities and the Bureau of Meteorology look at the risk of bushfires using the forest fire danger index, a combined measure of temperature, humidity, wind speed and the dryness, but not the amount, of fuel on the ground. Australia’s 2019 spring months of September, October and November were the worst on a record going back to 1950 for bushfire risk
‘Natural’ weather patterns?
There have been two other meteorological patterns that helped generate the extreme conditions Australia has been experiencing, and both these “modes of variability” were in “phases” that made conditions worse.
The Indian Ocean dipole was in a “positive phase”, meaning the Indian Ocean off Australia’s north-west was cooler than normal and the west of the ocean was warmer, positive dipole events draw moisture away from Australia and tend to deliver less rainfall but there is evidence that the extra greenhouse gases in the atmosphere are also impacting the dipole and another phenomenon, known as the southern annular mode (SAM).
A 2009 study found that positive dipole events “precondition” the south of the country for dangerous bushfire seasons and that these events were becoming more common. A 2018 study in the journal Nature Communications found the number of extreme positive dipole events goes up as climate heating continues. At 1.5C of global warming, the frequency of extreme positive dipole events doubles compared with the pre-industrial period.
The southern annular mode was in a “negative phase” as the bushfires took hold in November and December. This phase was generated by a sudden warming event in the stratosphere above Antarctica.
This caused westerly winds to track further north, blowing hot air across the continent into fire-prone areas, further fanning flames.
What role is climate change playing in the risk of fire?
The fires started in various ways: some by lightning, some by human actions, including arson. However, it’s the climate conditions that provide ample fuel for the fires to grow and spread before the fires ignited, Australia was already enduring its hottest and driest year on record. It’s summertime in the southern hemisphere, and the heat keeps rising.
Much of the severe heat was accompanied by brisk winds across much of Australia, which exacerbates fire risks and spreads blazes. “The intensity and size of bushfires in some areas has led to the creation of their own weather systems,” the Red Cross reported on January 8, “generating pyro cumulonimbus clouds, trapping heat and generating strong wind and lightning strikes, in turn sparking further fires.”
High temperatures, dry weather, and wildfires are not unusual this time of year. But the severity and continued persistence of these fiery conditions are alarming and fit the pattern of what scientists expect as the climate changes.[3]
CONSEQUENCE OF THE AUSTRALIAN BUSH FIRE OF 2019-20
Area burned
Since September, the fires have killed at least 25 people, including three fire-fighters, left entire towns in ruins and destroyed almost 2,000 homes as of 2 January, more than 12 million acres had burned – an area six times the size of the 2018 California wildfires the estimate has since increased to nearly 15 million acres, or around twice the size of Belgium, according to some media outlets.In NSW, the massive Gospers Mountain fire alone has burned more than 1.2 million acres, making it the biggest forest fire in Australian history one-third of the vineyards in South Australia’s Adelaide Hills have been lost.
[1] https://www.ga.gov.au/scientific-topics/community-safety/bus last seen on 30-1-2020.
[2] https://www.lifehacker.com.au/2020/01/w https://www.lifehacker.com.au/2020/01/what-causes-bushfires/hat-causes-bushfires/ last seen on 30-1-2020.
[3] https://www.vox.com/science-and-health/2020/1/8/21055228/australia-fires-map-animals-koalas-wildlife-smoke-donate last seen on 02-02-2020.
IMAGE Courtesy statista.org
Loss of wildlife
The damage to the environment and native Australian fauna is colossal one study estimated that 480 million animals in NSW may have been killed already, either during blazes or afterwards from lack of food, water and shelter and increased risk of predation.[1]
This figure only includes mammals, birds and reptiles and does not consider insects, bats or frogs. Sussan Ley, Australia’s environment minister, has said that up to 30% of koalas on the NSW mid-north coast may have perished because “up to 30% of their habitat has been destroyed” she added that the true impact on threatened koala populations won’t be fully understood until the fires stop and “a proper assessment can be made”.
The National Farmers’ Federation estimates more than 100,000 sheep and cattle have been lost. Army reservists have been brought in to help bury their carcasses.[2]
[1] https://www.chathamhouse.org/expert/comment/will-devastating-bushfire-season-change-australia-s-climate-stance?gclid=CjwKCAiA-P7xBRAvEiwAow-VaTfgyy8FeW6rcIDI0WgvmkBwVJizKDvYdYxqFV9rRFcQ5AeNoxfgyRoCg5QQAvD_BwE# last viewed on 5-02-2020.
[2] https://www.wwf.org.au/get-involved/bushfire-emergency#gs.wgpq5c last viewed on 06-02-2020
Image Courtesy wwf.org.au
Choking on smoke
For months, hazardous bush fire smoke has intermittently blanketed heavily populated areas, including Sydney, Melbourne and Canberra in Canberra on 1 January, air quality was more than 20 times above hazardous levels, leading to a shutdown of restaurants, shops, childcare centres, museums and government departments.
Plumes of smoke, dust and ash are visible from space and have even drifted thousands of kilometres east to New Zealand, causing skies to turn orange and glaciers brown.
CO2 Emissions
The bush fires are estimated to have pumped 350 million tonnes of CO2 into the atmosphere – roughly two-thirds of Australia’s annual emissions budget in 2018-19, according to NASA data. It may take a century or more for forests to absorb the CO2 released so far during this season’s fires, one expert told the Sydney Morning Herald.[1]
Heat and drought
Australia’s Bureau of Meteorology has confirmed that 2019 was the hottest, driest year on record the country is experiencing one of its worst droughts in decades and a heat-wave in December broke the record for highest nationwide average temperature of 41.9°C , Scientists have warned that climate change increases the likelihood and intensity of wildfires. The Climate Council says a warming planet is making bush fire conditions more dangerous than they were in the past, increasing the risk to people and property.[2]
HOW CAN ONE HELP?
- If you’re in Australia, Givit has a list of specific items needed by people and organizations affected by the bushfires.
- People with emergency response training can sign up to volunteer in Queensland.
- The World Wildlife Fund is collecting donations to restore habitats for koalas impacted by the fires.
- One can donate to the Australian Red Cross’s fire recovery and relief fund.
- One can also donate directly to the New South Wales Rural Fire Service, the Country Fire Service Foundation in South Australia, and the Country Fire Authority in Victoria.
[1] https://edition.cnn.com/2020/01/01/australia/australia-fires-explainer-intl-hnk-scli/index.html last viewed on 05-02-2020
[2] https://www.carbonbrief.org/media-reaction-australias-bushfires-and-climate-change last viewed on 06-02-2020
Author Analysis
The 2019–20 fire season in Australia has been unprecedented. To date, an estimated 18 million hectares of fire has cut swathes through the bush an area greater than that of the average European country and over five times the size of blazes in the Amazon.
This reflects previous predictions of Australian science. Since 2008 and as recently as 2018, scientific bodies have warned that climate change will exacerbate existing conditions for fires and other climatic disasters in Australia. What used to be once-in-a-generation fires now re-appear within 10–15 years with increased ferocity, over longer seasons.
In a country known for climate denial and division, debate has erupted around bushfire management and climate change. One of these is whether controlled burns are the answer to Australia’s climate-affected fire conditions.
There is no single risk reduction strategy. Controlled burning remains key, if adapted to the environment and climate.
But when three out of four seasons in a year can support destructive bushfires, there are clear limits to what controlled burning and other fire management techniques can achieve. Other ‘adaptation’ measures are also likely to provoke intense debate – including bush clearance. As one Australian expert offered to highlight where Australia has got to, families should probably not go on holiday to bush and beach during the height of summer when temperatures and fire risk peaks.
So, unless Australia is prepared to debate radical changes to where people live and how land is used, the limits to adaptation imply the need for mitigation. This means supporting ambitious global greenhouse emissions reductions targets. As research from Victoria, one fire-prone state in Australia, highlights(opens in new window), ‘the emissions pathway we follow is the largest determinant of change to many variables [such as temperature] beyond the next few decades.’