A plastic sheet is not necessary when the soil is clayey. The presence of nearby crested newts makes it likely that these new ponds will be colonized, according to specialists.
Is it enough to dig a hole in a forest to create a pond? During a weekend of protest against the motorway project of theA133-134activists of the Earth Uprisings made two water holes in the Bord forest (Eure), located 20 kilometers from Rouen. The purpose of these large puddles is to attract crested newts, a protected amphibian species whose presence activists hope will help discourage the highway project.
On Twitter, reactions quickly poured in, from opponents of the Earth Uprisings. “If it were necessary to illustrate the ignorance and the stupidity of these fanatics: believe that all you have to do is dig a hole to create a pond. And it says ‘environmentalists’ frankly, itis pitiful! Go back to town and shut up forever“for example split the deputy RNJean-Philippe Tanguy. So will the newts go “get well”, as the environmental movement has declared, and eventually benefit from stagnant water? To find out, franceinfo sought the opinion of several experts.
The first criticism, recurring on social networks, concerns the impermeability of the holes dug by the activists, which are not sealed with a plastic sheet. Stéphanie Morel, biodiversity and ocean network facilitator at France nature environment, ensures that it is entirely possible to create a pond without plastic sheeting, provided that the nature of the soil lends itself to it. “If it is clayey, the water will be retained. Before man and plastic sheeting existed, there were many water holes”she quips.
However, the soils of the forest of Bord have a layer of clay with flint in depth which allows the presence of ponds, explains to franceinfo Clément-Blaise Duhaut, project manager at the Conservatory of natural spaces of Haute-Normandie, who has carried out a pedological reference (which concerns the study of soil matter) of the region. “But we have several types of soil in the forest of Edgehe adds. To know where to dig, the surest way is to carry out a soil survey. The presence of an already existing pond nearby remains a good clue to the type of soil.”
On Twitter, the group of militant naturalists @NaturalistsDTR having taken part in the action of the Uprisings of the Earth, assures that the pond was “dug in clay soil, near vegetation indicative of obvious hydromorphy” and “this ‘hole’ will fill up at the latest during the rains next autumn”. “Gradually, the pond will fill up. Amphibians and possibly newts will settle there”says Sonia Saïd, ecologist and researcher at the French Office for Biodiversity.
“The pond will probably not be used until next year”
“There is never a guarantee that a species will come. Other amphibians can. But if the newt is already present in the forest, it is likely to settle there”, adds Stephanie Morel. The holes “were positioned near another pond, teeming with larvae of salamanders, newts, toads”say the @NaturalistesDTR on Twitter. “Densifying a network of ponds, especially in these times of drought, is good. And then, it makes the population of newts present more resilient. When you have a single pond, the risk is that someone, thinking well, release a fish in the pond, and there, it’s a disaster for the larvae of newts”adds Cédric Baudran, naturalist herpetologist (specialist in reptiles and amphibians) at the National Forestry Office.
Experts generally welcome the initiative to promote environments conducive to crested newts, but explain that several criteria must be met to create an optimal pond. “The crested newts like ponds that have a certain age, where the vegetation has been able to develop. Often, they are dug in autumn so that the rains fill them and that they are functional in the spring during the reproduction phase. this time of year, it’s a bit late. It probably won’t be used until next year.” advance Jean Cassaigne, secretary of the Herpetological Society of France. “You have to allow a year or two, the time for the sediments to clog, for the pond to be fully operational. Ideally, newts prefer large areas, not very shaded. It is rarer to find them in the forest”analyzes Cédric Baudran.
A shrinking population
“Creating ponds is always very good for newts, especially in the context of global warming where there is less and less water”, continues Françoise Serre-Collet, herpetologist at the National Museum of Natural History in Paris. The ephemeral holes are, according to him, a blessing for newt populations, since the absence of fish allows the larvae to grow. “VSIt doesn’t matter if the pond dries up after a while. The newts do not stay there all year, they mainly join it to reproduce in the spring”adds Stephanie Morel. However, the drying should not be too premature, to give the larvae time to complete their maturation. The risk of too little space “is that in case of drought, it dries up before the end of the development of the larvae which is about 60 days. In the present case, on the photo, we say to ourselves that the hole is perhaps a little small”concedes Jean Cassaigne.
Finally, regarding the damage caused to tree roots by digging, ecologist Sonia Saïd wants to be reassuring: “No, there’s no reason for two exposed roots to endanger them. A tree doesn’t hold on just two roots, fortunately”. On the other hand, “road projects that partition habitats” threaten biodiversity, regrets Stéphanie Morel. “Newts on either side of a road can no longer genetically mix. It’s harmful.”
The population of crested newts is already decreasing, because its habitat is shrinking more and more, according to Françoise Serre-Collet. To provide a favorable environment for their reproduction, the amphibian specialist encourages you to dig cavities “leaving them to fill themselves. The amphibians and newts will come.” A piece of advice that only applies to newts and amphibians. The regional health agency advises humans to avoid stagnant water as soon as the fine weather arrives, as it promotes the proliferation of the tiger mosquito, a vector of disease.