- Some good news on the front of fires that consume the south-east of Australia since September: the most important of the "mega-fires", out of control for almost three months, has been mastered, announced the firemen on Monday . And the rain is expected soon.
- Australia does not see the end of the tunnel, and summer is far from over. It also remains to be seen how it will recover from this wave of fires, which has already ravaged 8 million hectares.
- The flames have endangered complex ecosystems, including koalas and other emblematic species of the island, on which attention is focused today, represent only a tiny part. Restoring this biodiversity could take decades.
Survival by moving? A petition, signed by several thousand people, was circulating on Monday on the sidelines of the fires ravaging Australia. His goal: that the koala be introduced in New Zealand, rich in eucalyptus, the staple food of the marsupial. A solution that is difficult to achieve technically and that would be very expensive, says Philippe Grandcolas, research director at the CNRS and the National Museum of Natural History (MNHN). Another potential problem is that of introducing an invasive species into a new environment, in this case New Zealand. "But it is limited with the koala, which does not reproduce at great speed", tempers the systematist.
Invasion or not, Wellington cut short this initiative. The objective of the New Zealand government is not so much to welcome endangered animals as to help its Australian neighbor regain control of the fires. So, he says, that koalas "remain in their natural habitat". Especially since according to Philippe Grandcolas, “the distribution area (of this animal) greatly exceeds the south-east of Australia, ravaged by flames. It is not the most endangered species today. "
And therein lies the whole problem, explains Philippe Grandcolas: "Efforts are focused on the most emblematic species of the region: koalas, kangaroos, wombats ... But again, koala is not the only animal to save ”. To be convinced, we must dwell on the estimates of Chris Dickman, specialist in conservation biology and ecology of Australian mammals. The first, which spoke of 500 million animals killed by the flames in Australia since September, had been taken up all over the world. Since then, the fires ravaging the south-east of the island continent have spread even further, so that Chris Dickman has revised his estimate upwards. It now evokes a billion animals killed. The ecologist makes these calculations based on population density figures for these animals in the affected regions.
"One million billion animals"
The losses could be even higher, these population densities are not always known and Chris Dickman clarifying, moreover, that he took the estimates low. "Above all, he explains that he only took into account mammals, birds and reptiles," says Philippe Grandcolas. However, it is hard to imagine the whole life contained in a square meter of forest, and which is far from being limited to large vertebrates. This is true in the Bois de Vincennes, it is even more so in Australia, which hosts a remarkable and endemic flora and fauna [which only exists in Australia]. "
In The Conversation , last Friday, Philippe Grandcolas and Jean-Lou Justine, professor of parasitology at the MNHN, added insects, amphibians and parasites in the calculation to evoke a "million billion" animals dead in the flames since September. Ideally, plants, mushrooms should also be included. But we stop there. One million billion is already a figure that makes you dizzy enough. "We wanted to avoid paying attention only to the mammals, the animals that most resemble us and for which we often have the most compassion," explains Philippe Grandcolas at 20 Minutes . In an ecosystem, species are dependent on each other. All contribute to the balance of the environment. "
Mega fires that upset the balance
Taking this complexity into account also means being aware of the difficulty with which nature will be able to recover from these fires, which have already eaten up 8 million hectares in south-eastern Australia and are still continuing. "A fire is a natural element in the functioning of an ecosystem, that is to say normal and even necessary sometimes," begins Raphaël Gros, lecturer and researcher at the Mediterranean Institute of Biodiversity and Marine Ecology and continental (Imde), where he works on the vulnerability of ecosystems to fires and their ability to recover from them. Plants are also adapted to these fires. These are the so-called pyrophyle species, such as cork oaks in the Mediterranean or the eucalyptus trees [found in Australia]. "
The problem is that mega fires, like those against which Australia is currently fighting, upset the balance. "When everything is going well, in a region prone to fire, several fires generally break out each year, but over limited perimeters and not in the same areas from one year to the next," continues Raphaël Gros. Over time, spaces of different ages are created and this patchwork promotes biodiversity. By cons, touching large areas, a mega fire burns areas that should never have burned at a normal frequency. Everything then is a question of dose. The resilience of an ecosystem greatly diminishes the more it is subjected to frequent fires. "
A recolonization of nature that will take decades?
This is the first problem with these mega fires. The second ? It is still linked to the vast ravaged areas. "Once a fire has been brought under control, living organisms will naturally recolonize the environment," continues Raphaël Gros. For plant species, for example, there will always be seeds that have survived. If they are well adapted to poor soils - and they are after a fire - they will germinate easily. Sometimes from the first rains. But these species are often commonplace. They alone are far from restoring the biological diversity that existed before the fire. "
To fully restore an ecosystem, it is then necessary to wait for the seeds of other species to be brought back by the winds, runoff or transported by animals. A process that can take decades, assess both Raphaël Gros and Philippe Grandcolas. "And there is nothing to say that this recolonization will not introduce disorders into the functioning of ecosystems," said the latter. Some species will run out of food, others of habitats. This will not automatically lead to species extinctions, but population declines are to be expected. "
Too big for a man to do something?
Man can help promote the recolonization of burnt areas and restore the balance between species. "One of the priorities, often, is to enrich burnt soils," explains Raphaël Gros. In France, one of the techniques is for example to spread compost. But the solution can only be envisaged over a limited area… not over 8 million hectares ”
This is also the concern of Philippe Grandcolas. "Not only is the territory huge, but restoring ecosystems will not be the only priority of the Australian government. And to quote the 2,000 houses which, on the spot, have already gone on fire.
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