Australia has welcomed the heavy rains that have hit several regions since Saturday, January 18. They extinguished several fires, especially in the east and the south of the country, and the cooling temperatures made it easier to fight the devastating fires.
But after the storm, the sun may return. In several regions, “we are not even at the peak in the fire season yet. February is known to be particularly dangerous, especially in the south of the country, ”assures the BBC Richard Thornton, researcher at the Bushfire and Natural Hazards Cooperative Research Center, an Australian public institute for monitoring natural disasters.
Ever less resilient ecosystems
Above all, these fires that have ravaged the country since September will, even when extinguished, leave a lasting environmental footprint, both on the country and on the global climate.
For Australia, damage to biodiversity and ecosystems - sometimes unique - may, first of all, undermine natural balances for a long time. Fires can destroy “plant cover”, resulting in disruptions in the functioning of affected ecosystems. How can animals that survive fires feed afterwards? ”Asked Philippe Grandcolas, director at the CNRS Institute for Systematics, Evolution and Biodiversity, contacted by France 24.
Human efforts to save thousands of animals may not be enough if they have no natural habitat to return to after the fire season has passed.
>> Read: Fires in Australia: a natural disaster in the country of climate-skeptics
Not everything would grow back the same. "The ecosystems will have a different composition, either momentarily - the time that the natural environments adapt - or definitively, because certain species will have completely disappeared", details this biodiversity expert.
For him, it will be necessary to wait several months before being able to make a first assessment of the tribute paid by biodiversity. But whatever the amount of the addition, "the environments will be poorer, that is to say that there will be fewer species, which will also make them less resilient for the future", summarizes Philippe Grandcolas.
In nature, ecosystems are often endowed with redundant species, that is to say plants or animals which fulfill the same role, which makes the whole more resistant. The complete destruction of certain species will make natural environments less able to defend themselves.
It's a vicious circle. With each new fire season, ecosystems will be less able to cope and regenerate. And this is without taking into account the dynamics specific to global warming: periods of drought and fires are bound to accelerate and increase, depriving nature of the time necessary to recover. Until whole regions of Australia become unfit for life.
"Billions of tonnes of CO2 released into the atmosphere"
This depletion of soils is not only important for Australia. The destruction of forests will also have an impact on the global climate. Fires emit large quantities of greenhouse gases which are themselves responsible for global warming.
“We are talking about billions of tonnes of CO2 released into the atmosphere”, specifies Roland Séférian, climatologist at the National Center for Meteorological Research of CNRS and Météo France, contacted by France 24. Difficult, however, to quantify today with precision the magnitude of carbon dioxide emissions. "We will have to wait until the end of the year to get a measure of the effects of these fires on the 2019 carbon budget," notes the French researcher.
In any case, this carbon dioxide will not remain above Australia. "In one year, it will be redistributed equitably across the globe, which means that the effect will be much more global than local," said Thomas Smith, professor in environmental geography at the London School of Economics, contacted by France 24. .
A year 2019 that will leave lasting traces
But greenhouse gas emissions are only one side of this story. When forests grow again, they recapture this CO2. "The real test will therefore be whether these forests are capable of regenerating, which ones will do it and how quickly," notes Thomas Smith.
The fires ravaged large areas of eucalyptus forests and a few pockets of rainforest, mainly in Tasmania and Queensland (northeastern Australia). It is the latter which are the most important because "they have the 'carbon sink' effect [that is to say which encloses CO2, Editor's note] the most important", specifies the British geographer. "If we see an ecosystem change in these regions of forests that were tropical up to now, the impact will be more important for the climate."
These fires must also “be assessed in the more global context of the fires that ravaged Russia, Indonesia and the Amazon in 2019,” recalls Roland Séférian. So many disasters which, put end to end, “come to thwart the efforts undertaken by the States to try to reduce the emissions of greenhouse gases”, he notes.
For him, the Australian fires and their violence prove that we must no longer just fight against the inertia of certain States in the fight against global warming, but also against “an increasingly chaotic climate system with vagaries that play against us ”.
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