Bushfires have always been a part of Australia’s ecology and environment. Some of the country’s native floras have evolved to rely on bushfires for reproduction, and fire events have been an interwoven part of the ecology of the continent for thousands of years. Aboriginal Australians used to use fire to clear grasslands for hunting and to clear tracks through dense vegetation; however this was only in periods of high rainfall and in very small grassland zones bordering desert.
Bushfires can be triggered by natural causes such as lightning, but more frequently by man-made events such as arcing from overhead power lines, arson, accidental ignition in the course of agricultural clearing, grinding and welding activities, campfires, cigarettes and dropped matches, sparks from machinery, and controlled burn escapes. They spread based on the type and quantity of fuel that is available. Fuel can include everything from trees, underbrush and dry grassy fields to homes. Wind supplies the fire with additional oxygen pushing the fire across the land at a faster rate.
Strong winds also promote the rapid spread of fires by lifting burning embers into the air. This is known as spotting and can start a new fire up to 40km downwind from the fire front. Fires can also be spread by black kites, whistling kites and brown falcons. These birds have been spotted picking up burning twigs, flying to areas of unburned grass and dropping them to start new fires there. This exposes their prey attempting to flee the blazes: small mammals, birds, lizards and insects.
However, Australia’s climate has warmed by more than one degree Celsius over the past century, causing an increase in the frequency and intensity of heat waves and droughts. Eight of Australia’s ten warmest years on record have occurred since 2005. A study in 2018 conducted at Melbourne University found that the major droughts of the late 20th century and early 21st century in southern Australia are “likely without precedent over the past 400 years”. Across the country, the average summer temperatures have increased leading to record breaking hot weather, with the early summer of 2019 the hottest on record.
Heat waves and droughts dry out the undergrowth and create conditions that increase the risk of bushfires. This has become worse in the last 30 years. Since the mid-1990s, southeast Australia has experienced a 15% decline in late autumn and early winter rainfall and a 25% decline in average rainfall in April and May. Rainfall for January to August 2019 was the lowest on record in the Southern Downs (Queensland) and Northern Tablelands (New South Wales) with some areas 77% below the long-term average.
Bush fires kill animals directly and also destroy local habitats, leaving the survivors vulnerable even once the fires have passed. Scientists estimates that in the first three months of the 2019-2020 bushfires, over 800 million animals died in New South Wales, and more than 1 billion nationally. This figure includes mammals, birds and reptiles but does not include insects, bats or frogs. Many of these animals were burnt to death in the fires, with many others dying later due to the depletion of food and shelter resources and predation by feral cats and red foxes. They added that Australia has the highest rate of species lost of any area in the world.
Koalas are perhaps the most vulnerable because they are slow-moving. In extreme fires koalas tend to climb up to the top of a tree and curl into a ball where they become trapped. In January 2020 it was reported that half of the 50,000 koalas on Kangaroo Island off Australia’s southern coast, which are kept separate to those on the mainland as insurance for the species’ future, are thought to have died in the previous few weeks.
According to Wildlife ecologists when fires have passed, frogs and skinks are left vulnerable when their habitats have been destroyed. Loss of habitat also affects already endangered species such as the western ground parrot, the Leadbeater’s possum, the Mallee emu-wren (a bird which cannot fly very far), and Gilbert’s potoroo. Beekeepers have also lost hives in bushfires.
Kangaroos and wallabies can move quickly trying to escape from fires. However, the Guardian reported in January 2020 that dozens, maybe hundreds of kangaroos “perished in their droves” as they tried to outrun the flames near Batlow in NSW. The most resilient animals are those that can burrow or fly. Possums often get singed, but can sometimes hide in tree hollows. Wombats and snakes tend to go underground. The 2019-20 bushfire season is of notable intensity compared to previous seasons as it has burned an estimated 10.7 million hectares (26 million acres; 107,000 square kilometres; 41,000 square miles), destroyed over 5,900 buildings (including over 2,204 homes) and killed 29 people as of 11 January 2020.
An estimated 1 billion animals have also been killed and some endangered species may be driven to extinction. As of 2 January 2020, NASA estimated that 306 million tons (337 million short tons) of CO2 had been emitted. By comparison, in 2018 Australia’s total carbon emissions were equivalent to 535 million tons (590 million short tons) of CO2. While the carbon emitted by the fires would normally be reabsorbed by forest regrowth, this would take decades and might not happen at all if prolonged since drought has damaged the ability of forests to fully regrow.
(Md. Arafat Rahman, Asst. Officer, Career & Professional Development Services Department, Southeast University)
