Understanding forests, living with fire

Decades of merely utilitarian management have made forests in Europe more vulnerable to extreme fires. To address this threat, a change of direction is needed that respects their complexity, also addressing the taboo of controlled fires

Extreme fires – impossible to contain, due to their abnormal size or rapid and unpredictable development – are on the rise in many regions of the world. The climate crisis is one of the causes of the problem, but equally important is the management, often short-sighted and utilitarian, of forest heritage.

First the planting of monocultures and alien species, and then – in recent decades – their generalised abandonment that has filled them with easily flammable material, have made forests much less adaptable to environmental changes.

Paradoxically, the very efficiency with which we have learnt to tame smaller fires has ended up increasing the risk of more devastating ones. In front of this threat, a radical change of direction is needed, which involves a real understanding of forests, to the point of breaking a taboo: learning – under certain conditions – to live with fire.

Unnatural landscapes

Of the 160 million hectares of European forests, only 4% is in an almost natural state. 88% is the result of more or less invasive human interventions that have continued for decades or even centuries, and 8% of new plantations, often of trees of a single species and coming from distant areas.

These include Norway spruces, exported to much of central Europe from Scandinavia and the main European mountain ranges, and Douglas firs, of North American origin. But above all, in southern and Mediterranean Europe, eucalyptus. Introduced in the early 1800s from Tasmania and Australia, this species – mainly used for its cellulose – now covers 1.3 million hectares in Europe, 80% of which in the Iberian Peninsula alone.

Poor in biodiversity, composed of trees of the same size and age, forests with few species are vulnerable to parasites, diseases, drought and storms. And also to the effects of fires.

The natural composition of forests is in fact the result of a very long evolution that has made them perfectly adapted to the characteristics of fires in different regions.

Where fire is frequent, but not too intense or widespread, species capable of colonising the burned land thanks to the seeds carried by the wind often prevail, while where fires are more intense, but rare, "seeders" and "resprouters" prevail.

The former (which include Scots pines, acacias and eucalyptus) are able to thrive after fires thanks to their robust seeds, while the latter (many species of oaks, the Aleppo pine and widespread shrubs such as cistus) have protected vegetative buds underground.

Forests populated by species that are not in balance with the fires of a region (due to human action, climate change or both factors) become very vulnerable to fire.

The database developed by Fire-Res confirms that almost always the areas hit by extreme fires had a significantly lower diversity than the surrounding areas.

Resistance and resilience: two complementary concepts

To best manage forests where the human footprint is now unavoidable, it is necessary to know and be able to enhance their ability to survive the "fire test" in good health.
The resistance of a forest is the ability of its trees to survive a fire.

It mainly depends on the quantity of fuel (more or less dry wood, undergrowth and so on) and its continuity, both between one plant and another and vertically. In fact, the closer the trees are, the more easily the fire spreads. If it takes root on the foliage, the flames become taller and able to spread to other trees.

On the other hand, there is resilience, or the ability of the forest to return to health and provide its ecosystem services after a fire. Forests made up of different species are more resilient, those in good ecological health (that are not, for example, under stress due to drought or the proliferation of parasites).

Both parameters play in favour of prevention: the higher the resistance, the less likely it is that the fire will become extreme. Once it has reached this behaviour, however, resilience will make the difference.

The perfect “mosaic” does not exist

There is no single recipe for making forests resilient and resistant. For this reason, Fire-Res has reviewed the available studies and developed its own database to discover how the characteristics of forests influence the behaviour of fires in different contexts, as well as conducting meetings (Living labs) with the various actors to identify virtuous practices.

Extreme fires, it has been observed, more often hit shrubs and grassy expanses, while among tall forests, conifers are hit more than broadleaf trees. With the – very notable – exception of eucalyptus, responsible for some of the most devastating fires, especially in Portugal.

Surprisingly, in northern Europe, among the most flammable environments those stand out that were once humid and peat bogs, increasingly dried out by hot and dry summers.

However, the distribution of forests matters at least as much as the species. If the landscape is fragmented into a mosaic of different forests, perhaps interspersed with agricultural areas and other discontinuities, fires tend to be less extensive, or at least less severe. However, this also leads to a fragmentation of habitats, which must be carefully assessed on a case-by-case basis.

Reducing fuel

The possible strategies almost all have one thing in common: it is necessary to reduce the amount of fuel present in the forests, from dead wood to undergrowth, both to prevent fires and to make them less intense and widespread.

In the past, this material was removed with a certain frequency: on the one hand, the forests were managed more thoroughly, on the other, the people themselves who frequented would collect wood or graze their animals.

Today, removal is a delicate and expensive job, carried out – when it is done – mostly with mechanical means. Scientifically advanced and carefully contextualised approaches can guide these measures, reducing their potential ecological impact, and orienting them towards the precise aim of making it more difficult for a fire to become extreme.

A rigorous approach to forest dynamics is not in contradiction with more traditional methods that obtained the same effect, such as promoting silvo-pastoral activities within the forests. In some areas in the Pyrenees, these practices, supported by appropriate incentives, aim to increase not only resilience but also rural communities.

The forgotten role of fire

In the last century, humans have greatly improved their ability to fight fire, and at the same time a policy of essentially "zero tolerance" towards fires has been established.

It has been so easy to forget that, in fact, fire plays an essential ecological role for forests. By burning part of the undergrowth and necromass (dead wood), it puts nutrients back into circulation and provides young plants with the space to thrive.

Often, above all, in a forest it was the fires that brought about the reduction in fuel that humans had so difficultly achieved. With all the fires quickly suppressed, the forests were loaded with flammable material like a time bomb.

Aware of the beneficial role of fire, many populations, from Australian Aborigines to European farmers until a few decades ago, have never hesitated to set it, under certain conditions, to free up pastures and fertilise the soil.

These are certainly dangerous practices, especially in forests that have lost much of their resilience, which have not only been abandoned but criminalised. Today, however, faced with extreme and uncontrollable fires, it may be time to change our minds.

Prescribed fires: breaking a taboo

There is broad consensus in the scientific community that by setting “prescribed fires” in forests (carefully, in carefully planned areas and in suitable weather conditions) the risk of serious fires drops significantly for several years, with a lower ecological impact than other methods of fuel removal.

Living with fire also means knowing how to apply the approach that experts call “let it burn": sometimes, putting out a fire that is not too intense, perhaps in remote areas, can be counterproductive, costly and risky for rescuers. Firefighters themselves, after all, know that appropriate “tactical fires" can remove fuel from a dangerous fire.

There is no shortage of modern experiments with prescribed fire (Fire-Res is building a database to take stock of the state of these practices) and some forest management projects that include it, such as the Catalan Aran Valley and the French Western Pyrenees, are producing encouraging results.

At a continental level, however, living with fire is still taboo, especially in the centre-north of the continent, which until now has been less accustomed to its presence.

In a society accustomed to total control over nature, giving fire back its ecological role, as well as a weapon against extreme fires, can be an exercise in humility.

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