The French forest is in danger. The latest forest inventory, carried out by IGN (National Institute for Geographic and Forest Information), draws up a worrying observation on the state of the trees: in the space of ten years, the national average of their mortality has increased by more than 50%, with a spectacular leap this year. A situation that seems to be linked, in large part, to climate change. One thing is certain, “something abnormal has been happening for more than a decade”, underlines the IGN, contacted by 20 minutes.
Three regions are particularly affected by the phenomenon: the Grand-Est, Bourgogne-Franche-Comté where there is two to three times more tree mortality than ten years ago, but also Hauts-de-France where the increase in mortality reaches 130%.
Wood-eating insects and fungi
“This increase is due to the fact that the trees are exploited by the timber industry and to the recurrence of episodes of drought and climatic conditions, which are both difficult for the trees and conducive to xylophagous insects. Indeed, when it is hot, these insects, which attack trees, proliferate. This is particularly the case for softwoods such as spruce which is particularly affected in the Grand-Est and in Burgundy, ”explains the IGN.
The other scourge is a fungus that strikes down ash trees in northern France. Arriving in France 15 years ago from the northeast, it is now present everywhere in France. “As it has long since settled in Hauts-de-France, it is in this region that it is doing the most damage for the moment”, specifies Nathalie Derrière, head of the inventory results department at the ‘IGN. Of course, the other regions where the ash tree is very present will soon feel it passing.
Declining forest productivity
“Overall, we see a 10% drop in forest productivity,” continues Nathalie Derrière. This means that the trees grow more slowly and produce less wood. A phenomenon related to stress when there is not enough water and it is too hot.
This decline, quite significant over a period of less than ten years, is cause for concern for forest managers and operators. The fourth largest in Europe, French forests are playing an increasing role in the ecological transition, in particular to decarbonize the construction sector or develop renewable energies.
More vulnerable forests
Its surface area is twice as large today as it was 200 years ago and 20% larger than in 1985. But the fear of further overexploitation of the forest is beginning to dawn. “The exploitation of wood is more and more sustained, but the volumes of trees available are constantly decreasing, deplores Nathalie Derrière. We don’t have a crystal ball, but the forest won’t take it long, especially if it’s in pain. »
Already, the question of the species to be replanted arises. In an article from Youmatter, Michel Loreau, CNRS research director, warns. “In forestry, a logic of monoculture was put in place in the second half of the 20th century, centered above all on the most productive species. Logic that has made forests more vulnerable.
“Wood production will suffer with global warming, recalls the researcher, the diversity of species can therefore play a positive role and will allow us to have forest ecosystems that adapt better to climate change. »