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

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

But what will happen to these devastated natural places over the years? How fast do trees grow to regain their original shape? What role do people play in this reconstruction? 20 minutes Ask yourself these questions and try to answer them with the help of two experts on the subject, who emphasize the importance of monitoring fire outbreaks, diversifying species and combating climate change, which outweighs the damage. Because of our environment.

What happens to the forest destroyed by fire?

Photographs of burnt forests, sometimes plucked from centenarian trees, accumulate over the years. Once the fire is brought under control and extinguished, they have a heavy workload to recover. And they will regain their luster only after a few decades.

A year after the fire that affected Var in 2021, we have certainly found “some seeds, some shoots” but we are still far from the structure of the forest and places will “keep the marks of the fire for another two to three years”, Eglantine Goux-Cottin, Consulting President of Engineer in Environment and Forestry (ICEF) considered 20 minutes.

“It all depends on the vegetation kit, the trees, the species that were present before the fire as well as the soil type,” said Brigitte Musch, head of the National Forestry Office’s (NFB) Genetic Conservatory of Forest Trees. The more leafy the trees, like Gironde oaks, the more likely they are to resprout from the stump.

For Aleppo pines, which are found in Mediterranean forests, seeds released during a fire will be able to germinate the following spring. However, it also depends on the severity of the fire. And what we have seen this week will “complicate things further due to the violence of the flames which in places exceed 100 meters in height”, warns Brigitte Musch.

When to transplant trees?

Again, this will depend on structure, forest species and fire severity. “If the root system does not burn, the plants will be able to start again and we will see something next year, but considering the surface area affected in the Gironde, we will have to replant in the affected areas”, Brigitte Musch hopes.

But before a replacement can be thought of, several fronts of struggle are organized. First, you have to “fight the wind that risks blowing away the humus”, essential for regrowth, then “remove burnt wood, cut, plan to grow… all this will take a year or two”, guess-tt -she.

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

The other trick is to let nature take its course. The duration of natural regeneration will depend on the environment, context, forest species, whether it is temperate or Mediterranean. But typically, “after ten years, the trees start to form themselves, then it takes 20 to 30 years to find the same structure as before the fire. Finally, at 70 to 100 years, we will recover a forest with interacting and functioning ecosystems,” Eglantine said. Gox-Cuttin explains.

“The best solution is to support this natural regeneration, to monitor and follow up before transplanting at any cost,” he emphasized. In fact, when humans intervene, it takes about the same amount of time because plant growth remains the same.

What trees to plant?

For Brigitte Bush, these deserts are an opportunity to try new things, to experiment with silviculture methods, to test other species… Because if certain trees are more adapted to these fires, such as Aleppo pines or cork oaks, “Today, they are more susceptible to these fires.” Can’t support the increased intensity and frequency”, explains Eglantine Gox-Cuttin. They are increasingly “water stressed due to increasingly extreme drought periods. Forest areas are under stress.

A mistake to avoid at all costs is planting the same species in a single location. Diversity is indeed an effective resource for the regeneration of an ecosystem. “The most resilient forests are those with the greatest biodiversity,” agrees Eglantine Gox-Cottin. Then there is the need for a mix of species with deciduous trees, conifers as well as Mediterranean species.

And what topography to adopt?

According to Brigitte Musch, the space between the trees is “a question that somewhat stirs the community”. In the question of fire, it is better not to let the tops touch each other to avoid spreading too quickly. At the same time, it is also necessary to fight against ferns and other tall grasses that encourage the initiation of fire and thus prevent excessive light from entering the soil. Especially since “the closer the trees are to each other, the more resistant to climate change a selection will be made”, ONF’s manager abounds.

Moreover, fire is not the only threat. “The way of planting will affect the structure of the forest, if it is too dense, we will have very tall trees, very thin trunks, continues Eglantine Gox-Cottin. In this case, there is a risk of stress with more fragile trees in the face of 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 fire outbreaks and, above all, fight against global climate change due to which this threat is more intense and more frequent. year year And today, France is losing forests because they burn much faster than they grow.

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