Beyond the tiger mosquito and the Asian hornet, which resurface every summer in the news, there is relatively little talk about invasive alien species. Yet they represent the second biggest threat to biodiversity, just after habitat loss – and ahead of global warming.
If they are generally harmless in their area of ??origin, these exotic species, plants or animals, become invasive when they proliferate where they are introduced, often by chance, according to globalization, and thanks to a climate. adequate.
Their demographic explosion then affects the other species present and the ecosystems, until becoming a driving force of the disappearance of the species.
“Not all traveling species become invasive,” observes University of Lausanne biologist Cleo Bertelsmeier, author of several books on ant sociality. Of the species that change their environment, only 10% manage to establish themselves. And of that 10%, a tenth has a detrimental impact on other populations and ecosystem functions. We don’t know why, although they are generally harmless in their native era. One of the most likely theories is that they originally co-evolved with predators and competitors that limited their expansion, but by being introduced to another area they escape their control. As long as the climate is favorable to them, and if global warming can help them, their population explodes. »
Focus on three of these problematic and poorly known insects to the general public, whose development is favored by global warming.
“We thought this species would remain limited to the Mediterranean,” says Cleo Bertelsmeier. But in recent years, it has also been found along the Atlantic coasts and in Switzerland. A specimen has, for example, been seen in Nantes, in Brittany. Their presence is influenced by the oceanic climate, which gives fairly mild winters, but global warming also affects the habitat and makes it very favorable for this species. »
The Argentine ant is one of the hundred most dangerous species listed by the IUCN for their impact on biodiversity, and in particular on fauna. Its invasive presence prevents other species of ants from surviving, which can pose a real problem when it comes to rare or endemic species.
Its establishment also has consequences for other insects. Predatory and numerous, they are very effective in capturing prey, from beetles to bees, and in dominating local resources.
Difficult to guard against it, explains Cleo Bertelsmeier: “It is possible to act against the Argentine ant when the population is small and localized, but currently, because it is a supercolony, there are hundreds thousands of queens… These are the ones you have to touch to control the population, and given their number, it’s very complicated. »
When its presence is noticed, the affected trees and those surrounding them for 100 meters should be felled and burned. A radical and rapid reaction nevertheless makes it possible to limit the infestation.
It is a global scourge, mostly concentrated in regions with a Mediterranean climate, but it is also found in Asia and in South and North America.
“It has managed to distribute itself in fairly warm or tropical regions and is taking advantage of global warming, underlines Cleo Bertelsmeier. As the temperate regions warm up, this favors it. Germany, Norway, Sweden or northern France also risk being affected one day. »
Great pest, it is difficult to control, even with pesticides. INRAE ??is currently trying to reduce the populations by releasing sterile males.
