The reason given here therefore concerns the survival of the pearl mussel which tends to disappear from our waterways, where it was nevertheless very present in the past, and of the thick mussel, another variety.
Let us point out from the outset that the beaver does not destroy the mussel by making a mussels-fries-beer feast every evening based on pearl mussels. But the dams it builds slow the flow of rivers, causing the creation of sediment that prevents the mussel from surviving.
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Eighty mussels
In the Anlier and Rulles watersheds, attempts to re-introduce pearl mussels were carried out in the early 2000s via the European Life program – which aims to protect endangered species. Now, there are a few dozen of them living their lives in a stream in the Anlier forest – there were 80 of them, under the age of 15 in 2017. Did the significant European resources invested at the time in the reintroduction of mussels have been effective given the low number of individuals in these rivers? We are not competent to judge this. But the ambition for the pearl mussel in Wallonia has no limits, since there is talk of reintroducing nearly 6,000 by 2028.
We must also ask ourselves why 99% of the pearl mussel population disappeared from our rivers during the twentieth century. It is in any case not the fault of the beaver which had disappeared from our regions the century before, hunted for its meat and its secretions used in perfumery. It is in fact also the hand of man that got the better of the mussels in our rivers. You surprise me! Indeed, their disappearance was the result of a reduction in water quality due largely to polluting products dumped in the fields, the scarcity of mollusk food resources, and the presence of livestock along the river courses. water and clogging of river beds.
But why then favor the pearl mussel and the thicket mussel, protected species over the beaver, an equally protected species? On the side of the Public Service of Wallonia, we consider that the beaver is a “species whose conservation status is considered favorable in the continental domain, with a positive trend, given that this species has become common and is still expanding”. If we continue to zap them every year, it is not certain that it will continue to expand, especially since it is a species that “self-regulatesexplains Frédéric Raes, member of the beaver group at Natagora. The latter also tells us that he has nothing against the pearl mussel and that he is not “a mold specialist”. According to him, nevertheless, Wallonia “would be the only one in Europe to have this approach to things”.
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The presence of pearl mussels in a river has some advantages. It filters, in fact, 50 liters of water per day and makes it of better quality. In the past, the pearls that certain mussels produced were highly sought after. It is said that a Catherine de Medici dress contained 32,000 pearls. Let us point out that today a pearl from a pearl mussel would no longer have any value.
The beaver and biodiversity
But the beaver also has its uses. By building dams allowing it to protect its habitat and its descendants, it slows down the flow of waterways, which is valuable in the event of very heavy rain. The marshy biotope that develops thanks to these dams is also valuable for biodiversity. Through its action, it also allows rivers to overflow and therefore fill groundwater.
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Two questions remain. Why today are these two species no longer able to coexist when two hundred years ago, this was the case? And if we find that another protected species is harming the pearl mussel, will we also eradicate it?
If these future reintroductions of pearl mussels by 2028 fail, then more than 150 beavers will have died for nothing.
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