Near Rouen. Will this emblematic mare of the Roumare forest disappear?
By Valentin Lebosse
Published on
Usually it is a large stretch of water of 1,500 m² which delights walkers and photographers passing through the Roumare forestclose to Rouen (Seine-Maritime). But in this summer of 2022 marked by drought and high heat, the Épinay pond is nothing more than a puddle in the middle of a silted basin.
The mare suffers from drought
“I have never seen the pond like this, it is going to die”, is alarmed Alain Boulard. Installed at Canteleu for 26 years, this retired photographer has been “often walking in the forest” and “always passing by the Épinay pond” to immortalize sometimes a couple of emperor ducks – “a rarity” -, sometimes the laying of amphibians.
This pond is the habitat of frogs, the breeding ground of toads, the heron’s pantry, the watering hole for wild boars and other game, not to mention salamanders, newts, etc.
This fragile ecosystem suffers from the lack of water. At Rouen, it has never fallen so little rain (8 millimeters) in a month of July, according to the statements of the Boos station. This rainfall deficit has lasted for several months and was felt early on in the forest ponds.
“From March-April, we knew that this year was going to be very complicated, book Francois Dugast, environmental specialist at the Rouen agency of the National Forestry Office (ONF), in charge of managing the Roumare massif. Water levels were already relatively low. »
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These environments turn out to be all the more sensitive to the absence of rain as they are, most of the time, not fed by a spring. “What the ponds store in autumn and winter evaporates the rest of the year,” says François Dugast. Nor can they rely on runoff, the Roumare forest being “perched above the loops of the Seine, on soils with a lot of pebbles which, by nature, have more difficulty retaining water”.
Thus, many of these forest pools have a so-called “temporary” regime. “She is dry for part of the summer,” explains the NFB agent. Which is not normally the case for the Épinay pond. Dug, it is said, in the Gallo-Roman period, “it is a fairly deep pond which always remains partially in water, even when it is very dry”. Until when ?
“We can’t replace the rain that doesn’t fall”
“Some time Since then, we have been in a cycle of very hot and very dry years”, notes François Dugast.
This is an issue on which the forester does not have the means to act. You can’t replace the rain that doesn’t fall from the sky.
Call firefighters to fill the ponds? “It remains very exceptional, we only do it as a last resort, when we feel that the fauna is suffering, that the animals of the forest no longer find where to drink. “Apart from the fact that “the firefighters have other priorities”, the specialist insists on “the monstrous financiers” of this type of intervention: “The Épinay pond alone represents several hundred or even thousands of meters cube. »
The forest is not a park that we would water like a garden to grow vegetables. The difficulty is to admit that these environments evolve, that ponds can dry up, disappear.
Endangered frogs and fish
This raises the question of the survival of certain species whose life cycle is strictly linked to these bodies of water. At the stage of green frogs whose “tadpoles spend a good part of the summer in the pond” after spring spawning. “This type of species runs the risk of no longer finding an environment favorable to its reproduction or of transferring it to other mares. »
The carp that inhabit the Épinay pond are also threatened. Even if, according to the ONF agent, “a forest pond is not intended to accommodate fish”: “They were introduced by people who would probably have supposed to get rid of them. Some fish have an effective effect on the balance of the mare, being the first to generalize the reproduction of amphibians whose tadpoles they consume. »
A lack of maintenance?
The fate of these animals concerns many visitors to the forest who have been moved by it on social networks in recent days. Among them, Alain Boulard expresses his incomprehension:
Our elders managed to keep mares for centuries and we wouldn’t be able to keep anything? It hurts my heart.
The pensioner fears an end similar to the sandstone mare, completely covered by vegetation. “In two, three years, it’s over! For him, “there is a lack of maintenance: I’ve never seen the mud cleaned out and no one uproots the plants that pump water from the pond anymore”.
François Dugast wants to put things into perspective: “The reeds experience strong growth in summer. Coupled with a problem of drought, this can give the impression that the pond is not maintained, that the vegetation is pumping all the water, when this is not the case. »
The environment specialist also warns against the uprooting of these plants:
Some plants are heritage species on which we cannot intervene anyhow.
In addition, this plant cover is necessary for the reproduction of amphibians and serves as shelter against predators, he adds. “That’s why we don’t try to heal and clean up all the ponds at the same time. Depending on their state of congestion, they may be interested in a particular species. »
The costly maintenance of forest ponds
Studies are therefore carried out on the fauna and flora, to define a management plan. This aims to “optimize” work on the ponds maintained by the ONF. “The Rouen agency intervenes every year on 40 to 50 ponds, between 3 and 5 in the Roumare forest, details François Dugast. We try to follow a ten-year rotation cycle between two cleaning operations. »
Thus, “several tens of thousands of euros” are spent each year “in terms of monitoring, species inventories, works”. Sufficient to maintain some 1,300 permanent mares in charge of the ONF in Seine-Maritime? In a context of repeated droughts, “we encounter material difficulties in keeping the forests at arm’s length”, admits François Dugast.
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