It is a small forest of a few square kilometers, nestled along the Ciron, in the hollow of karst gorges, in the south of Gironde. In some places, trees form a continuous vegetation cover over the river, a tributary of the Garonne. With a little luck and a lot of discretion, you will be able to observe rare and endangered species such as the European mink.
In this bucolic environment is a multi-millennial biological treasure: a unique beech forest, whose scientists have not yet understood all its secrets or the extent of its influence. However, it is threatened. The protection of the Ciron forest is one of the reasons for the mobilization of opponents of the high-speed line (LGV) between Bordeaux and Toulouse who demonstrated, on Saturday, October 12, in Lerm-et-Musset, a city bordered by the river . The railway project requires the construction of several crossings of the valley at the heart of which is the beautiful forest.
For Alexis Ducousso, the mystery arose during a random walk along the Ciron River. In 1993, while he was a researcher at Inra (which in 2020 became Inrae, National Research Institute for Agriculture, Food and the Environment), the Picardy scientist found beech trees at the water’s edge, in Pompejac. A rarity for this specialist forest genetics: “In theory they had nothing to do here”explains. The beech is common in the northeastern quarter of France and in Normandy. In the southwest, fagus sylvatica It is, however, non-existent, except for some very localized stations, and on the slopes of the mountains where it can find the freshness essential for its development.
The surprise of Alexis Ducousso soon becomes a field of study. Almost twenty years later, the discovery of fossilized coal in the neighboring city of Bernos-Beaulac will give even more scope to its discovery: carbon-14 dating reveals that gasoline survives on the banks of the Ciron for forty-three thousand years, which makes this beech forest one of the oldest French forests. The trees that form it are distant descendants of woody trees that found refuge in the hollows of the gorges in the middle of the ice age; In this case we are talking about a relict species.
Dieback
Although they have survived millennia of climatic variations, the inhabitants of the Ciron Forest are nevertheless at the mercy of other disorders. Seen from the sky, the deciduous trees that live on the banks of the river, beeches, but also oaks and lindens, form a narrow strip surrounded on both sides by the intensive forestry of the maritime pine, arch-dominant in the Gascony moors.
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