The high temperatures of fall have clearly driven the insects crazy. We saw the tiger mosquitoes sucking our blood until October, the Asian hornet buzzing outside its favorite period. In the past, France has seen many species arrive on its land without having been genuinely invited. The blue crab in the Mediterranean, American crayfish, the bullfrog which has become the terror of Gironde. And then, the golden jackal, halfway between the wolf, the fox and the coyote, normally distributed in Eastern Europe and Asia, appeared.
Should we fear the arrival of unusual animals or new diseases because of global warming? Are we going to come across new predators looking for a little freshness or warmer temperatures?
While it is difficult to anticipate which species will find their home in France and feel good there, “we can predict without risk of being wrong that the species which are in the southern part of France will move towards the northern part” , says Jean-Lou Justine, professor at the National Museum of Natural History in France and specialist in worms. “Global warming is obviously changing the environment of animals and plants. This might be a natural process, but it is, according to some researchers, a thousand times faster than normal. Certain species which were well established, with rapid changes, have more problems keeping their place because other species enter into competition and replace them,” points out Dirk Schmeller, researcher at the functional ecology and environment laboratory in Toulouse, specialist in mountain ecology.
France has seen many species arrive. The Asian hornet and the tiger mosquito are the stars of the genre. Although they were able to proliferate with the high temperatures, they did not arrive alone with their little wings. We know that the Asian hornet was found in a batch of porcelain from China, for example. “Similarly, someone brought the bullfrog back from the United States because he found its song harmonious,” explains Jean-Lou Justine. Bad idea. The large amphibian invaded several departments of Nouvelle-Aquitaine, eating everything in its path and finding no predator to contain its proliferation.
Health risks
A species becomes invasive when it is no longer in its original ecosystem, but we cannot predict whether it will find the conditions necessary for its proliferation. “In China, the Asian hornet is safe because it is at home, there are other species of hornets there,” explains Jean-Lou Justine. Once it arrived in France, it exploded.” “We introduce new species and if they are competitive, they can replace native species,” confirms Dirk Schmeller. The Asian hornet was introduced, the Varroa [une espèce d’acariens parasites] which kills bees, it too was more or less introduced with bees that come from far away. We also have pathogens, such as Batrachochytrium dendrobatidisa fungus that comes from Asia and affects amphibians, it was imported with frogs all over the world.
Until now, humans were the main actor in the disruption of ecosystems by removing species from their environment. Global warming is not going to fix anything. For around ten years, we have seen flatworms, called platyhelminths, arrive in France. Some species come from Australia, others from South America or Southeast Asia. This time, the climate is to blame. ” For the Bipalium kewense [originaire d’Asie du Sud-Est], until now limited to the small southern border of France, we have made climate models according to the evolution of the climate and we realize that these platyhelminths will invade all of Europe, certain species could even go as far as in Sweden,” points out Jean-Lou Justine. These platyhelminths are all predators, they eat earthworms, which are very important for the soil.”
Another fear: they could participate in the transmission of a nematode called Angiostrongylus. It is a parasitic worm whose larvae can be found in slugs or in these famous flatworms. “A few years ago, an Australian teenager challenged himself to eat a raw slug, he ended up paralyzed before dying. Although there is no danger for rats, in humans, the nematode larvae are lost and can become dangerous if they get into certain areas of the body,” points out the researcher. Even if the slug is cut between two lettuce leaves, or crushed, the nematode larvae can remain alive for some time and be very dangerous once ingested. We are starting to find cases ofAngiostrongylus in the south of France.
One and the same ecosystem for everyone?
Certain species such as rats or blackbirds can adapt to many conditions. But most species need a particular habitat to survive and, with global warming, they will perish. “Let’s take a mountain species, it needs a specific habitat and to find food,” describes Dirk Schmeller. With global warming, she sees a disconnect between food and habitat and it will disappear.” We could imagine migrations towards the north to find the same conditions. “But when Antarctica and the poles are thawed, the polar bear will no longer be able to find its habitat, it will become extinct. We can imagine this scenario for many specialist species,” continues the researcher.
Invasive species, heat… Imagine a world where, on both sides of the planet, there are only bedbugs, pigeons and rats left. It’s science fiction, but in the long term, we could end up with impoverished and simplified ecosystems. “The more species an ecosystem contains, the more capable it is of resisting attacks. A simplified ecosystem with very few species is less resistant. This may be the reason why we are seeing more and more invasive species, they arrive in already degraded environments that they find it increasingly easy to invade,” worries Jean-Lou Justine. We still have time ahead of us – several hundred years, according to Dirk Schmeller – before we see a simplified ecosystem on a global scale.
“What we see happening are ecosystems which lose part of their biodiversity and which are degraded,” confirms Dirk Schmeller. Water and air lose quality because the ecosystem services to make them clean no longer function in the same way. Cyanobacteria are establishing themselves in many high altitude lakes, this is a sign of degradation. When cyanobacteria die, they release toxins, the water becomes less good for the health of humans and animals.” Under these conditions, we can very well imagine proliferations of tiger mosquitoes or pathogenic microorganisms. They no longer have predators due to the loss of biodiversity. Seeing thirsty wild animals disembark, in search of more hospitable lands, would ultimately be quite good news compared to the world that is emerging.