How long and how to find a forest before the fires?

20,600 hectares of forest went up in smoke in the Gironde in one week, 15,007 hectares in 2021 and 17,400 hectares throughout France in 2020 … Every year, forest and vegetation fires destroy the French forest area. And with climate change, they are becoming more intense and more frequent.

But what happens to these ruined natural spaces years later? How fast do trees grow back to regain their original structure? What role does man play in this reconstruction? 20 minutes has asked itself these questions and is trying to answer them with the help of two specialists in the case, who insist on the importance of monitoring the outbreak of fires, diversifying species and combating climate change, which weighs more and more on the damage caused by our environment.

What happens to forests destroyed by fires?

The images of charred forests, devoid of their sometimes century-old trees, accumulate over the years. Once the fire is brought under control and extinguished, there is still a heavy workload to restore them. And they will not regain their glory until decades later.

A year after the fires that hit Var in 2021, we will certainly find “a few seeds, a few shoots”, but we are still far from a forest structure and the sites will retain “traces of the flames for another two to three years”, believes Eglantine Goux-Cottin, President of the Consultative Engineer in Environment and Forestry (ICEF), contacted per. 20 minutes.

“It all depends on the vegetation set, trees, species that were present before the fire, as well as the type of soil,” adds Brigitte Musch, head of the Genetic Conservatory of Forest Trees at the National Forestry Office (NFB). The more leafy the trees are, like the oaks in the Gironde, the more likely they are to start again from their stumps.

For Aleppo pines found in Mediterranean forests, seeds released during the fire could germinate the following spring. However, this also depends on the intensity of the fires. And what we saw this week “will make things more complicated given the violence of the flames, which in some places exceeded 100 meters high”, warns Brigitte Musch.

When can trees be replanted?

Again, this will depend on the structure, the nature of the forest and the intensity of the fires. “If the root system is not burned, the trees will be able to start again and we will see some next year, but given the affected surface area in the Gironde, we will have to replant in the affected areas,” predicts Brigitte Musch.

But before thinking about replanting, several battle fronts are organized. First of all, you need to “fight the wind that risks sweeping away the humus”, essential for regrowth, then “take out the charred wood, cut, raise the plans … All this will take a year or two”, estimates-tt – she.

How long does it take for a forest to regain its appearance before destruction?

The second technique is to let nature take its course. The duration of natural regeneration will depend on the environment, the context, the species of the forest, whether it is temperate or Mediterranean country. But in general, “after ten years, the trees begin to structure themselves, then it takes between 20 and 30 years to find a structure similar to the one before the fire. Finally, from 70 to 100 years old, we will restore a forest of interactions and a functioning ecosystem, ”explains Eglantine Goux-Cottin.

“The best solution is to support this natural regeneration, monitor and follow up before replanting at all costs,” she insists. Yes, when man intervenes, it takes about the same time because the growth of the trees remains the same.

Which trees to plant?

For Brigitte Busch, these desert lands are an opportunity to try new things, to experiment with forestry methods, to test other species … For if certain trees are more adapted to these fires, such as Aleppo pines or cork oaks, “today they can no longer support the increased intensity and frequency of these fires, “explains Eglantine Goux-Cottin. They are increasingly” water stressed due to increasingly extreme droughts. The forests are under pressure.

The mistake to avoid at any cost is to plant the same species in a single room. Diversity is truly an effective asset for the rebirth of an ecosystem. “The most resilient forests are those with the most biodiversity,” says Eglantine Goux-Cottin. It is then necessary to favor mixtures of species with deciduous, coniferous and Mediterranean species.

And which topography should one adopt?

The space between the trees is “an issue that excites society a lot”, according to Brigitte Musch. For the issue of fires, it is better that the peaks do not touch each other to avoid too rapid spread. At the same time, it is also necessary to fight against ferns and other tall grass, which promotes the start of fire, and thus prevents too much light from penetrating into the ground. Especially since “the closer the trees are to each other, the more a selection of the most resistant to climate change will be put in place”, abounds the leader at ONF.

Moreover, fires are not the only threat. “The way of planting will affect the forest structure, if it is very dense, we will have very tall trees, very thin trunks,” continues Eglantine Goux-Cottin. In this case, there is a risk of stress with trees that are more fragile to storms, you have to find a good balance ”.

In general, to prevent these forest fires from multiplying, it is necessary to monitor forests, maintain them, prevent flare-ups and, above all, globally, to combat climate change, due to which this threat is more intense and more frequent each time. . year. year. And today, France is losing forest areas because they are burning much faster than they are growing back.

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