Recent rains have finally brought the Australian fire season to a close. Between September, 2019 and January, 2020, an estimated 20% of Austalian forests burned. Fires are natural, but the scale of latest fire season was off the charts.
Australia's annual average forest loss to wild fires is typically well below 2 percent.
Fires in New South Wales were not contained until February 13th, and not completely extinguished until March.
Many species have evolved adaptations that allow them to survive fires and outcompete neighboring species subjected to burning. Noteworthy here are the eucalyptus forests of Australia. They have faced periodic burning in dry Australian climates for many millennia. The strategies they have evolved to survive these fire prone conditions include production of leaves covered by a thick layer of waxes that grow vertically to reduce prolonged drying in direct sunlight, high leaf oil concentrations that make fires burn more rapidly, thick barks to insulate internal tissues, and proliferation of seedlings and leaf buds upon exposure to fire.
So, burned Australian forests did not simply die. Regeneration has already begun.
Aussies are sharing heartening images of the regeneration that’s already taking place among burnt out trees.
However, there are numerous reasons to suppose that Australian forests will not simply return to previous dynamic equilibrium cycles of fire, regeneration and growth.
A major determinant of the Australian climate is the direction of air flow over the Indian Ocean driven by temperature differences from east to west in what is known as the Indian Ocean Dipole. Surface air flow from Africa towards Australia typically means more rain in Australia, while flows towards Africa and away from Australia increase the likelihood of drought. Recent trends indicate that these flows leading to drought in Australia are increasing in frequency and magnitude.
The 2019 drought occurred at a time where the Indian Ocean Dipole was at a record positive level.
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Professor Abram said positive IOD events had become stronger and more frequent, particularly since the 1960s.
This translates to more frequent and intense Australian droughts, which leads to more wildfires. As mentioned above, the extent of the fires the past summer were beyond the ranges seen in previous fire seasons. It hit areas that have not seen fires, and, thus, impacted species not adapted to periodic burning. This was due to an extended period of drought that spread vulnerability to fire across much of the country, including rainforest areas that have not burned for millions of years.
Typically moist, these environments don’t burn. But unprecedented fires have now ravaged more than 11 million hectares in eastern Australia, penetrating these strongholds that rarely, if ever, faced fires before.
Furthermore, these changes in the Indian Ocean Dipole and Australian droughts are not occurring in isolation. Conservative modeling estimates that human-induced climate changed has led to a 30% increase in the likelihood of fire kindling conditions as observed this past year. Meanwhile, empirical observations suggest that the fire risk in Australia has increased four fold since 1979.
In the 2019-2020 fire season, an estimated 1 billion animals were killed by fires, and there were more fires affecting more areas of Australia than ever before.
The number of fire alerts in New South Wales in 2019 was roughly 4 times higher than any time in the past two decades.
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Fires are also burning in and around Australia’s AZE (Alliance for Zero Extinction) sites, threatening the very existence of entire species like the Wollemi pine tree and the Corroboree frog.
Finally, the onset of rain does not end the possibility of environmental devastation. Heavy rainfall following drought and fire leads to flooding and power outages, hinders emergency response crews, and erodes freshly exposed soil.
Because of the drought we're in, we have very dry landscape and just enough of that rain can cause not only flooding but landslips — or essentially soil erosion — so that's certainly something that we're very mindful of
In short, the unprecedented scale of the latest fire season in Australia and the likelihood that it could repeat due to climate change raise serious concerns about future fire seasons, and whether resiliency to recover from periodic burning will be overmatched by increasingly frequent and devastating burning.