It is one of the most important wetlands in France. One of the most fragile too. About sixty kilometers long between Nantes and Saint-Nazaire, classified as a protection site Nature 2000, the Loire estuary is suffering from climate change and, more particularly, from repeated episodes of drought. This is the worrying observation of communities and associations before the adoption of a action plan in 2023.
“There are a lot of factors that impact the species of the estuary and their habitats. There are human practices whether port activities, water management, agriculture, fishing, hunting, leisure activities too. But there are also, and increasingly, the consequences of climate change, a subject that goes far beyond our department,” explains Chloé Girardot-Moitié, vice-president of the Loire-Atlantique department and president of the Natura 2000 estuary committee.
A phenomenon already observed in recent years, the lack of rain, combined with a rise in temperatures, has had the effect of drying out the reedbeds and meadows of the Loire from spring onwards. The insect population has declined sharply. And their predators, foremost among which are migratory birds, have weakened or deserted the area. “The deficit of breeding birds is 30 to 50% compared to last year alone, it’s huge,” warns Hubert Dugué, head of European programs at the Acrola ornithological association.
“An international responsibility”
“By the end of April, the little waders had left their nests to other more favorable areas. We had never seen that. This means that there has been very little local reproduction. The birds observed in the estuary were “extremely thin”. “Their feathers were marked, signs of a growth pause due to a lack of food. Some, like the warblers, if they don’t pass through the estuary with 5 g of fat, they have no chance of reaching Africa to spend the winter there. We also saw extremely weak young storks taking flight,” laments Hubert Dugué. These difficulties also apply to amphibians and even bats, several of whose refuges “have been abandoned” in recent months.
The lowering of the water level also weakens certain species of fish, in particular pike, tench and rudd, which have experienced “significant mortality episodes”, notes Vincent Mouren, director of the Loire-Atlantique fishing federation. Another effect of global warming: the temperature of the water in the river increases, reaching 30°C in the nearby ponds. “It’s insidious but it modifies reproduction and weakens the stand. Some exotic species are proliferating to the detriment of others, such as catfish, Asian gudgeon or sunfish,” says Vincent Mouren.
There are local courses of action helping to improve the situation: protection of plots, prohibition of inputs, promotion of virtuous agricultural practices such as late mowing of meadows… Will this be enough? Probably not. “French estuaries, and that of the Loire in particular, play a major role as a migratory stopover. We have to keep them in good condition. It is high time to take substantive action. It is an international responsibility”, insists Hubert Dugué, of Acrola.