After flooding rains come fires
Australia’s wettest November on record was in 2021. Halfway through the month the Bureau of Meteorology (BOM) declared the arrival of a La Niña climate event for the second year in a row. Rain continued relentlessly on Australia’s east coast throughout the summer, and this year, 2022, the January–March period became the wettest first three months of a year ever recorded in parts of New South Wales. Even in April, rainfall was still 27 per cent above average for Australia as a whole.
The El Niño-Southern Oscillation (ENSO) – of which drenching La Niña rains are part – is one of the world’s most significant sources of weather variability. Scientists are increasingly finding its impacts, both wet and dry, are being exacerbated by climate change.
The unprecedented summer–autumn rains led to flooding that severely affected northern NSW towns, including Lismore and Byron Bay. Some east coast regions affected by flooding in 2022 had yet to fully recover from the 2019–20 bushfire crisis.
For many of us, Black Summer may now seem a distant memory – particularly with the COVID pandemic occupying so much of our lives since then. But some experts are concerned that all the recent rains have significantly increased the chance of severe bushfires recurring soon. This was always on the cards after Black Summer showed what was possible in a warming world. However, fires may return sooner than anticipated.
It seems counterintuitive, but rains and fires are closely linked. Wet periods lead to lush growth of eucalypts and other foliage in the bush, which creates a higher fuel load once dry years inevitably return.
When we again endure an extended period of drought, as south-eastern Australia experienced before Black Summer, much of the current verdant growth will dry out, creating perfect kindling for large bushfires to once more rip through our eucalypt-dominated forests.
Experts led by Dr Pep Canadell, chief research scientist at CSIRO’s Climate Science Centre, reported last November in a study in the open-access journal Nature Communications that “fuel loads and their distribution and structure are key determinants of fire spread, intensity and severity”.
For the analysis, Pep and his team collated data on Australian fire seasons back to 1930. They found climate change has played an ever-increasing role in driving fire weather and in growing the amount of fire fuel.
“The highest years were actually right after La Niña years because the wetness across the continent really brings up the fuel loads,” Pep told reporters last year.
The BOM has reported there’s a chance we’re even going to have a triple La Niña, with wet conditions continuing through the summer of 2022–23. This could delay the return of severe bushfires, but might result in an even greater build-up of fuel before they return.
The advent of a double La Niña last year perhaps should have underscored the previous federal government’s efforts at the UN climate talks in Glasgow in November, when Australia’s pledges once more disappointed the international community (see Earth View, AG 166). But with the recent change in government and a groundswell of support for candidates promising climate-change action, we may now have much stronger national efforts to limit emissions and slow global warming.
This can’t come soon enough. Along with other climate change impacts such as severe bushfires, extreme El Niño events, which can cause acute droughts, are predicted to increase in frequency. The likelihood of an El Niño being extreme is predicted to as much as double over the next decade.
