It is a predator that lives at night, moves very slowly, but proliferates at full speed: a species of invasive flatworm, coming from Argentina, is invading the gardens of France and Europe, potentially threatening biodiversity, according to a study published Thursday.
"It can invade the neighboring garden in a few months"
The species "Obama nungara" - which means "flat like a leaf" in an Amerindian language, without any link with the former American president - is reported on three-quarters of the French territory. It is notably spread via the trade in potted plants, according to data mainly based on participatory science, and published in the scientific journal PeerJ. " It's a pretty story that started in March 2013: an amateur naturalist observes in his garden of Cagnes-sur-Mer (Alpes-Maritimes) a bizarre worm, and sends his photo" on specialized networks, tells the AFP Jean-Lou Justine, professor at the Museum of Natural History in Paris, who directed the study.
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Intrigued, the scientists set up a vast network of participatory sciences, which collects in five years several hundred reports, mainly in France but also in Europe (United Kingdom, Spain, Portugal, Belgium, Italy and Switzerland). Several species have been identified, but “Obama nungara” seems to dominate. These are mostly dark brown specimens, measuring 5 to 10 cm. Thanks to molecular analyzes, scientists manage to find its origin: Argentina, where the species landed via potted plants. "Once a species is in a garden, it may move very slowly, it can invade the neighboring garden in a few months," explains Pr Justine.
" Billions of people in 70 departments "
"This is a classic phenomenon for invasive species: its presence is discreet at first and we only notice it when it has invaded a whole part of the territory," analyzes the researcher at the Museum. There are "billions of individuals" , listed in more than 70 departments in mainland France. "One of the surprises was not to find it at altitude, probably because the nights are too cold there," added the scientist.
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What do we blame him for? To be a predator eating soil animals (earthworms and snails), and to be a “non-indigenous species that has no place in the soil ecosystem” . The study does not give figures on the importance of predation, and therefore on the exact ecological impact, concedes the researcher. "Invasive is not synonymous with harmful: it means that proliferation becomes very visible, and that it is potentially dangerous for the ecosystem. If it is a predatory animal, it will necessarily decrease the population of animals it eats, ” says the researcher.
How to get rid of it? "We do not know. You can crush them or burn them, but there will be as many afterwards. ”