Less than a month after being released, the first eight water buffalo from the Etang de Cousseau nature reserve (Gironde) already seem to be acclimatizing well to their new environment. “Above all, they are already eating the plant species that we had identified and that we wanted them to eat” underlines Xavier Chevillot, director of Sepanso Aquitaine, the association managing the reserve and at the origin of this initiative.
This species, particularly adapted to wetlands, in fact aims to carry out grazing work complementary to that carried out by Landes sea cows, other herbivores themselves reintroduced into the reserve thirty-five years ago. This rewilding program, carried out with the Rewilding Europe association, should notably make it possible to reduce human mechanical interventions within this nature reserve.
“Repairing the mistakes of the past”
“Natural environments in Europe have been very strongly modified by man for millennia,” recalls François Sargos, curator of the Cousseau pond nature reserve. All large wild herbivores – the aurochs, the bison, the wild horse, etc. – were eliminated to be gradually replaced by large domestic herbivores. However, these were key species of the ecosystem, a sort of “landscape engineer”. And when we remove an element from the ecosystem, it often causes cascading problems. »
It is from this observation that the Etang de Cousseau nature reserve, located in Lacanau, a stone’s throw from the Atlantic coast, has given itself the mission of “reestablishing the functionality of ecosystems. » “The role of nature reserves is also to show that we can repair the mistakes of the past and restore dynamism to nature,” insists François Sargos. We are not here to just do pure conservation. »
Experimental duration of three years
Certainly, the species of water buffalo reintroduced in Cousseau, related to the Asian water buffalo Bubalus arnee, is not the one who lived here several millennia ago. But it is the only one that could play this complementary role to sea cows, in particular thanks to its large hooves allowing it to move easily in the swamps. “The goal is to see if these animals can adapt to this type of marsh, feed on the vegetation there, and stay there all year round, when the cows are forced to go back into the forest from of January,” continues François Sargos. The reserve has in fact suffered an imbalance since the reintroduction of sea cows: the latter graze the 600 hectares of marshes from June to December, when the water table drops, but they abandon it to its fate in winter to return to the area. more forestry.
If this reintroduction – carried out on an experimental basis for three years – succeeds, it will be extended with the arrival of a greater number of water buffalo. “We don’t yet know how many are needed, but clearly eight animals are not going to be able to maintain 600 hectares of marshes” recognizes the curator of the nature reserve.
In France, “only two other natural sites, the Marais de Sacy (Oise) and the Courtils de Bouquelon Nature Reserve (Eure), have used these animals,” notes François Sargos. The species is, however, widely used in many European countries (Germany, Netherlands, Belgium, Greece, Italy, etc.), “where it is satisfactory. »
First reintroduction of insect in France
And this is not the first reintroduction carried out within the Cousseau pond reserve. “Each species has a defined role in nature, and the major idea that we are pursuing is to recover the entire functionality of the ecosystem, brick by brick” explains Xavier Chevillot. Even if it may seem more anecdotal at first glance, another species, Scarabeus laticollisa… pill-rolling dung beetle, was also brought back.
“Thirty-five years ago, when we reintroduced sea cows, this brought about thirty species of dung beetles, which returned naturally” explains Xavier Chevillot. “But in this big family, he was missing Scarabeus laticollis. VSThis is how we called on Jean-Pierre Lumaret, one of the most eminent dung beetle specialists in the world. » Professor emeritus at the Paul-Valéry University of Montpellier, the latter collected specimens in the Mediterranean area to bring them to Gironde and thus carry out the first insect reintroduction operation in France.
“Very conducive environment”
Around sixty of these “pill rollers”, which shape balls from dung to lay their eggs, had already been reintroduced in 2023. At the beginning of May, around a hundred additional individuals were brought. “It is a species which was present on the site before disappearing and the soil is once again favorable to it, because the sea cows which are here are not subject to preventive anti-parasitic treatments” underlines Cyril Forchelet, scientific mission manager . In the absence of these chemicals, the dung is of better quality and provides a favorable environment for dung beetles.
Also called coprophagous beetles, these promote soil fertility by transforming organic matter into mineral matter, which is then reused by plants. “They also make it possible to disperse the material and thus avoid the concentration of parasites” adds Cyril Forchelet.
“We will continue to identify the species that are missing and which will promote biodiversity,” indicates François Sargos. And to warn: “We certainly won’t stop there…”
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