Authored by Tom Roberts, Elizabeth Yin, and Charles Hogger. Maps by Maria Leasure.
Bushfires are integral to the Australian environmental landscape. Many native plants are fire-prone, and some depend on fire to regenerate. Bushfires start due to a combination of dry fuel in the form of leaf litter or other organic debris and an ignition source (generally lightning strikes or human activity). The speed at which the fires spread and the intensity at which the fires burn depends on wind speed, ambient temperatures, slope angle, the amount of fuel available, and the amount of moisture in the fuel.
Summer 2021-2022 Forecast
Figure 1 forecasts areas anticipated to have higher than average wildfire risk and lower than average risk.
- Due to the influence of La Nina conditions, above-average rainfall is forecast over eastern Australia through summer 2021-2022.
- However, above-average bushfire potentials are still forecast over most of central New South Wales due to grass growth.
- Dry conditions in Western Australia are also likely to lead to above-average bushfire potentials in the western regions.
- Below-normal fire potentials are forecast across portions of the Australian Capital Territory, eastern New South Wales, and eastern Victoria due to increased rainfall and the recovering vegetation from the 2019-2020 bushfire season.
The bushfire season typically runs December-May in southern Australia, May-October in northern Australia, and August-March in central Australia. Southeastern Australia, including southeastern South Australia, Victoria, and southern New South Wales, is one of the most fire-prone areas worldwide. Figure 2, below, shows the intensity and distribution of bushfires 2016-2020. The previous 2020-2021 bushfire summer season was unusually weak and the quietest fire season in a decade due to La Nina conditions resulting in a cool and wet summer.
This year, the Australian Bureau of Meteorology has declared that a La Nina event is underway in the tropical Pacific Ocean and is likely to persist through January or February 2022. This will result in above-average rainfall and lower temperatures in eastern Australia. The wetter and cooler conditions have reduced the fire risk in some areas, but have at the same time increased vegetation growth and thus potential fuel.
Forecast models indicate an above-average fire potential across much of New South Wales, especially west of the Great Dividing Range and in the Cooma Monaro with high amounts of crop and grassland. The Pilbara, Gascoyne, and Murchison - as well as the Swan Coastal Plain, Jarrah Forest, and western areas of the Esperance Plains and Mallee Bioregion in Western Australia - are forecast to have above-normal fire potentials due to above-average temperatures during the summer months and above-average grass fuel loads.
Although the ranges of New South Wales have high grass fuel load, the above-average rainfall forecast across the coast and ranges is likely to result in lower bushfire risks. However, if the increased rainfall does not eventuate or is inconsistent, the ranges could have an increased risk of fire potential.
Below average fire potentials are forecast across portions of the forested areas of the Australian Capital Territory, eastern New South Wales, and eastern Victoria. This is due to above-average rainfall over the past few months resulting in high soil moisture and smaller fuel amounts from the still recovering vegetation burnt in the 2019-2020 bushfire season, especially in forested areas, which take longer to re-accumulate than grasslands. Normal fire potentials are forecast across the Australian Capital Territory grasslands over the summer due to average rainfall and temperatures.
Impact of Bushfires
Bushfires can result in loss of life, property damage, economic losses, and infrastructure damage. Power outages are possible in places due to damaged substations and transmission lines or intentional power cuts to prevent infrastructure damage or help prevent the spread of fires. Smoke from wildfires can hurt the eyes, irritate the respiratory system, and worsen chronic heart and lung diseases. Smoke may also worsen symptoms for people with pre-existing respiratory conditions - such as respiratory allergies, asthma, and chronic obstructive pulmonary disease (COPD). Extensive soil erosion is possible across burn scars during bouts of rainfall due to loosened soil and an increase in runoff from the lack of interception by trees and foliage.
Supply chain disruptions are possible, especially if bushfires burn across highways and roads or approach large population centers. Bushfires can also lead to evacuations, road closures, and ground transport diversions. Disruptions to arterial roads are possible, and the scarcity of alternative routes in some areas means that significant transport disruptions are possible at times. While authorities are experienced in minimizing the potential impact, roads in remote regions are likely to be disrupted for longer periods than urban roads due to their relative inaccessibility. Authorities could close routes in bushfire complexes and evacuate communities due to fire activity and the needs of response operations. Traffic flows could also be disrupted after authorities lift evacuation orders during reentry periods.
Low visibility from smoke and possible ashfall could contribute to traffic delays and congestion and prompt short-notice flight disruptions if bushfires occur near airports. Railways can also experience occasional cancellation of services and long delays.
Many warehouses, factories, and other supply chain-related businesses tend to be located in the suburbs with a higher likelihood of being affected by bushfires as compared to city centers. Bushfires can destroy crops and livestock, resulting in losses. Businesses are also likely to be adversely affected by the supply chain disruptions especially if they require transportation of perishable goods.
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