A study on the cost of invasive species has just been presented at the World Conservation Congress. The figures are impressive: almost nine billion euros for France in 25 years, more than 1 billion worldwide since 1960.
If this study aims to alert about the damage caused by these exotic species that participate in the disorganization of ecosystems, its conclusions are underestimated. The numbers refer only to almost 100 exotic species in France, while there are more than 2,700.
Fish, insects, rats, butterflies that come from elsewhere and settle in metropolitan France and overseas territories have an environmental, health and economic cost. On the Loire, for example, fishermen are concerned about the development of an Asian mollusc that directly harms local species. “The corbicula is a mollusc native to the Mekong, a tropical river in Vietnam, Laos, Cambodia,” explains Philipe Boisneau, who represents French freshwater fishermen.” As there is a logging port in Nantes and a port in Ho Chi Minh City, we suppose that when we carry water in the ballast tanks of freighters to balance them in Ho Chi Minh, we release some water from the Mekong into the Loire estuary to balance the load and probably these swimming larvae arrived on the Loire. “
“Since then, all French rivers have been invaded by this corbicula, which is capable of filtering out all the phytoplankton that is the basis of the biological chain of our freshwater systems. Freshwater fish stocks have dropped dramatically by 60 to 80% .”
Philippe Boisneau, representative of freshwater fishermento France
The combination of human action and global warming allows, therefore, the migration of exotic species. In France, in the top trio of species that cause the most damage, we find in first place the ambrosia, a plant native to North America established in Auvergne-Rhône-Alpes. More than half a million people have suffered from allergies, with a total health cost estimated in 2016 at 40 million euros.
Then there are mosquitoes that are vectors of diseases, including the tiger mosquito, whose area of ​​implantation is growing. For David Renault, one of the authors of the study, it will be difficult, therefore, to return to the already entrenched species, but it is time to invest more heavily in prevention: “Without a doubt, it will be difficult to act immediately against species that are already invasive and that have very high population levels for some of them today,” he said. says David Renault. “Even so, we can detect the arrival of new species early and fight when they arrive, when they settle down. And then, in order not to find new species of mosquitoes in ten years, the fruit flies, which will bring new problems”, he continues.
This first cost study was carried out by a consortium of researchers led by the CNRS, the University of Paris Saclay and AgroParis Tech.