“Natural, free-growing, species-diverse forests resist fires very well”

2023-08-17 08:00:04

The fires which affected the Landes de Gascogne last summer marked the spirits, reaching tens of thousands of hectares. The finding is frightening. But can we compare the “forest” of the Landes to a natural forest? It is important to understand that the “forest” of the Landes is not a real forest, but a plantation, a field of trees. This is essentially composed of maritime pines, naturally flammable softwoods whose natural reproduction is stimulated by fire (they are therefore called “pyrophiles”).

Also read the forum: Article reserved for our subscribers Poetess Hélène Dorion: “In the midst of the flames, what are we missing to feel that we are what is burning with the trees? »

As the trees there are almost all the same age, the spread of fire through crowns of the same height is facilitated. Finally, these pines were planted on former wetlands and bogs dried up by excessive drainage. These thirsty organic soils burn deep. Fires are also facilitated by needle litter, which is hydrophobic. Everything therefore combines to ensure that fires are frequent and difficult to control! And yet, the forests of the Landes were originally composed of leafy species: oak groves, alder groves or willow groves depending on the humidity of the place, all of which constituted real firebreaks.

Another reality, another place: the Canary Islands, plagued by intense droughts for several decades. The fire that ravaged 10% of the island of La Gomera in 2012 stopped at the gates of the primary forest. Why such a difference ? Free-growing natural forests, extremely diverse in species, are very resistant to fires.

False debate

Firstly because they are mainly composed of hardwoods, which are much less flammable than softwoods. Then, because their trees are of very different ages. Larger and older ones have thick bark that is more resistant to flames. A natural forest has many layers of vegetation, which help retain moisture and slow down the wind. The dense deciduous undergrowth maintains a humid atmosphere. In addition to the evapotranspiration of the dense forest cover, the large dead woods are rich in water, which they return to the undergrowth. Finally, the deep soils of the free-growing forests retain rainwater.

Would preventing fires therefore require better management of forests, which are regularly cleared? In the Landes, where the understory is absent or regularly eliminated, many pine forests have nevertheless been completely destroyed. The recurrent maintenance of the forest, in the silvicultural sense, is therefore certainly a false debate. In this context, it should not be forgotten that 90% of fire outbreaks are of anthropogenic origin. However, cleared forests encourage human penetration and irresponsible behavior.
Even a dense, poorly penetrated Mediterranean forest very rarely burns in its natural state. Unfortunately, Mediterranean forests in a good state of ecological conservation are rare.

You have 33.78% of this article left to read. The following is for subscribers only.