Do we want to alleviate forest fires? Let the forests grow old

It seems like a challenge to the prevailing narrative, but “primary and mature forests are just less prone to fire danger than human-modified forests,” a scientific analysis by the EU Joint Research Center concluded in 2023.

However, “the difficult thing is to find forests in which the trees die of old age,” reflects José Antonio Atauri, coordinator of the mature forests project at the Fernando González Bernáldez Foundation. Very difficult in Europe, where these forests represent only 3% of the forest area, but even more so in Spain where they are “a minuscule percentage,” adds Atauri. “They have been logged for a long time despite the fact that they are very valuable for being refuges for biodiversity, a genetic reservoir and resilient to climate change.”

Before extolling the virtues of a mature (or primary) forest, it is worth asking: how do we know if we are looking at one of them? Defining it is not as simple as it may seem at first glance. “The first thing, of course, is that the forest has always been a forest or for a very long time because it has to have very old trees and that takes at least two centuries,” says Atauri.

The Life-Red Bosques project describes that these masses “have remained untouched by human intervention, evolving naturally.” In Spain they are very rare because almost all forest masses have been modified by human use for centuries. The remains that we can find are scattered and isolated. “They are remote and many inaccessible, so they have not been exploited. They were not profitable,” summarizes Atauri.

This aging process provides them with their own characteristics. On a walk through these forests you should be able to find:

Fire resistance

Finding some of these forests is very difficult both in Spain and in the Mediterranean region, which is precisely one of the hot spots of the offensive of forest fires that regularly advances fueled by climate change. Greece, Italy, France and Portugal are the prominent leaders of super destructive fire in Europe as seen in recent seasons. And they barely conserve 2% of mature forests between them.

The widespread idea of ​​conserving a forest by maintaining tall trees and little else as a safeguard against flames is breaking down. “The complexity of species, a strong microclimate effect and the moisture content in decomposing thick trunks makes them less exposed to the risk of fire,” argues the JRC research for Europe, which expands: “A large amount of fine remains are associated with of firewood with an increased probability of ignition and spread in meteorological conditions conducive to fire.”

Vayreda tells elDiario.es that “it is a complicated answer, but there are indications that tell us that mature forests have elements of resistance to fire. There are more resistant species and the diversity of varieties means that fire will always cause damage, but surely more trees will survive if they are older, taller and, thus, more separated from the undergrowth.”

Undergrowth: “Vegetation of bushes and shrubs that grows under the trees of a forest,” defines the Royal Academy. But perhaps it is better known (especially when talking about forest fires) as weeds.

Undergrowth: “The thickness that forms a multitude of bushes,” describes the RAE. The etymology of this last word gives many clues about how it has been considered historically: it comes from the Latin term malitia which means “evil”. And that perspective has dominated when managing forests, making the undergrowth the first candidate to be eliminated as the main task of fire prevention in many mountains.

We don’t like the term weeding. The understory provides a lot of diversity and is inherent to forests. If you eliminate it, it returns in a short time, even though you have spent a lot of money removing it because clearing is the most expensive.

Jordi Vayreda
— Creaf researcher

“Why do we call it weeds?” The Creaf researcher asks. “We don’t like the term weeding. The understory provides a lot of diversity and is inherent to forests. Removing something inherent is counterproductive and eliminates important functions,” he explains. A forest, when mature, is a complex ecosystem. It has understory species.

Furthermore, according to this doctor in Terrestrial Ecology, clearing this vegetation is not a good business in general terms either because “if you eliminate it, it reacts very quickly and returns in a short time, even though you have spent a lot of money removing it because clearing It is the most expensive. “It is a type of action that can be valid in contact areas between vegetation and population – he admits – in the so-called urban-forest interface, but in general it is not a good practice.”

And what to do then? Jordi Vayreda explains that “perhaps it would be better to try to maintain a dense tree cover through which less light enters because that allows you to control the undergrowth.” The idea is that without light it doesn’t grow as much. “If you make a cut and remove tree cover, the undergrowth will grow freely. If you allow the forest to become mature and old there is more coverage, shade-tolerant species grow that burn little, and even when there is a fire the fire will have a hard time reaching the treetops when it arrives. “That complexity of species will make it more resistant.”

What the research says

Evidence is accumulating about how forests resist being left to age. A review of the severity of 1,500 fires over 30 years on the West Coast of the United States revealed that legally protected forests—which were able to mature and contained higher levels of biomass and fuel potential – had, in fact, suffered less severe fires than areas with strong human management, especially by the forestry industry. A few years later, another study found that “intensive forestry characterized by young, homogeneous trees was a significant vector for fire severity rather than the amount of biomass.”

Even clear felling (which removes all the specimens from a forest stand) has led to “a greater frequency of very severe fires,” according to a team from the Australian National University in 2022. These are studies in North America and Australia, but offer conclusions.

Fire is inherent to Mediterranean forests. But now the majority of fires are caused by humans (in Spain only between 5% and 6% have a natural cause) and that makes them a different phenomenon from the natural fire regime to which the trees had been adapting: “Even these ecosystems can experience degradation due to human-caused fires and the effects of climate change,” explains the Joint Research Center.

Atauri adds that if a large fire breaks out, “these mature stands of course burn, but they slow down the flames, which can give an opportunity to stop them.” “Very thick wood burns worse,” he continues, “thick trees burn more difficult and contain more moisture, so simplifying forests, in addition to being very expensive, does a disservice to other services.” And he concludes: “Leave the sticks alone [los árboles] It stops the fire, but that is not a forest and that is one of the great difficulties that exist.”

Jordi Vayreda understands that forest management “that increases the maturity of the forests, even if little by little, is surely a good idea.” In other words, apply the elements of maturity to those that are not or as Atauri says: “Imitate old forests to be more resilient.”