On this January morning, on a beach in Teste-de-Buch near Arcachon (Gironde), nearly a thousand withered Christmas trees are converted into windbreaks to contain the advances of the ocean.
Each year, a team from the National Forestry Office (ONF) supervises around ten children, aged 10 to 12, to store these conifers on the dune cut by the winds.
The dune has retreated 90 meters in a few years
Coastal erosion, a natural phenomenon of sediment loss, under the effect of winds, waves and tides, causes the coastlines to recede by several meters in places on the country's sandy coastline. At Teste-de-Buch, on this beach below the pine forest burned during the megafires of summer 2022, the dune has retreated by 90 meters in recent years.
The small fir trees, pulled from their base with enthusiasm by children equipped with protective gloves, will act as “windbreaks” and, thanks to their thorns, prevent the sand from flying inland, explains NFB technician Mathieu Brugère. Covered over the months, these dead trees will “refill” the holes in the dune line and their organic contributions will nourish the sandy plants – oyat, gourbet – set up by the ONF to “maintain” the sand at the top of the dune, specifies the specialist.
Offshore, the appearance of sandbanks modifying the currents has allowed a slight “re-fattening” of the beach over the past two years. “We take advantage of these moments of respite to capitalize on the sand in the necessary places,” adds the technician, before urging the children to pile the fir trees into a gap in the dune. This was dug by the trampling of vacationers arriving from the parking lot, “entirely covered with sand” during the fall because the dune no longer protects it.
“These kids are very attached to their beaches, to their nature”
For Karelle, 11 years old and already accustomed to these operations carried out with her class or the municipal youth council of the town, “it is important so that people can go to the beach without there being sand on the road “.
-“In a few years, you will say: I worked on this dune,” says the mayor (DVD) Patrice Davet to a little boy with gloves full of green thorns, once the hole is filled. “These kids are very attached to their beaches, to their nature. They also remember the fires of two years ago. We amplify this attachment by making them do environmental tasks. This is our future, we want to educate them in this sense,” highlights the elected official.
15,000 trees each year
A total of 15 skips, or more than 15,000 fir trees, are dumped every January on the town's beaches. This model of “gentle management” of erosion has been deployed for around ten years on the sandy beaches of the Bay of Biscay (from the Pyrénées-Atlantiques to Vendée), as well as on certain dune ridges in the north of the country ( Manche and Pas-de-Calais).
According to scientists from the Nouvelle-Aquitaine Coast Observatory, associating the BRGM and the ONF, the dune is retreating by 1.7 to 2.5 meters per year on the sandy beaches of the South-West. The phenomenon could threaten 6,000 homes there, if nothing is done, by 2050.
