Australia is currently grappling with the most severe bushfire season it has experienced in 20 years, bringing the issue of increasing forest fires worldwide to the forefront of public discourse. This article sheds light on the reasons for such events, the unique conditions in Australia that facilitate them, and the broader environmental implications they carry.
Understanding Bushfires
Bushfires, or forest fires, are frequent occurrences in dry and hot seasons across the globe. These fires are fueled by easily combustible materials such as dry leaves, grass, shrubs, and deadwood. Ignition usually occurs naturally, for instance through lightning strikes, or accidentally via discarded cigarette stubs. The speed and direction of wind play a crucial role in spreading these fires, which usually end due to rain or lack of additional vegetation to feed upon. There have been instances, however, where fires are intentionally ignited, often leading to controversy and international concern.
Australian Bushfire Tendencies and Reasons
As the driest inhabited continent, Australia regularly sees bushfires, particularly during its summer season that starts in October. Around 70% of the land comprises arid or semi-arid regions, facing less than an average annual rainfall of 350mm. Australia maintains approximately 134 million hectares of forest land, with bushfires being a common occurrence each summer. Data from the Australian government revealed that between 2011-2016, more than 40% of this forest land had experienced at least one fire.
The 2020 Devastation: Unprecedented Bushfires
The current Australian summer has seen forest fire spread and intensity on a scale previously unseen. So far, these fires have affected over 10.3 million hectares of forest land—an area equal to the size of South Korea—with significant loss of human and animal life. The main reasons behind this unusual occurrence are a prolonged drought, positive Indian Ocean Dipole (IOD) events, and rare stratospheric warming over Antarctica.
Factors Contributing to the 2020 Bushfires
The years 2017-2019 marked the driest 36-month period ever in New South Wales, with 2019 being the warmest and driest year for Australia as a whole since 1900. Daytime temperatures on average were 2°C higher than normal and the overall rainfall was 40% below normal, creating optimal conditions for ignition and spread of forest fires.
| Year | Average Temperature Increase | Average rainfall |
|---|---|---|
| 2017 | +1.5°C | 45% below normal |
| 2018 | +1.8°C | 43% below normal |
| 2019 | +2°C | 40% below normal |
In 2019, these preconditions were augmented by one of the most potent positive IOD events and unusual stratospheric warming over Antarctica, leading to temperatures ranging from 30°C to 40°C higher than normal approximately 10 to 50 kilometers above the Earth’s surface.
Connection with Climate Change
Experts suggest that climate change has amplified the severity and impact of natural disasters such as bushfires. Weather conditions are becoming increasingly extreme, with fires starting earlier and spreading more intensely each season.
Impact of IOD on India and Australia
The IOD refers to the difference in sea-surface temperatures in the eastern and western Indian Ocean, which either aids or disrupts moisture supply to Australia. The unusually cold eastern Indian Ocean in 2019 contributed to deficient rainfall over Australia. The Indian monsoon showed a delayed withdrawal and higher strength due to the persistent positive phase of the IOD, which is also suspected to have delayed the transition of the monsoon trough from the Northern Hemisphere to the Southern Hemisphere, affecting the onset of the Australian monsoon.
