In these days of heat waves, large fires are occurring in the Mediterranean, especially in Turkey, Greece and Italy. Similar situations are occurring in other parts of the world (California, Siberia, etc.). And we experienced something similar last summer. It is therefore understandable that I am repeatedly asked if all these fires are a consequence of climate change.
The short answer is that climate change facilitates fires (it favours the spread of fire and extends the fire season), but it does not determine that there will be fires. I try to answer in more detail below.
The ingredients
At least three ingredients are needed for fires to occur, and they must occur simultaneously. These ingredients are: ignitions (natural or human), dense and continuous vegetation (fuel) and drought. The relationship of these factors with fires is not linear, but of threshold type. That is to say, there is a level of ignitions, continuity of vegetation and drought from which the probability of fire increases exponentially (it shoots up).
When the three thresholds are exceeded, mega-fires of difficult control are generated. And these thresholds vary with weather conditions. Specifically, they are very low when temperatures are particularly high (heat waves), humidity is low or winds are strong. In other words, under these conditions, less ignition, less fuel and less drought are needed for fires to start. Therefore, under these particular conditions fires are much more likely, as long as there are ignitions and fuel continuity.
The recent increase in droughts and heat waves is associated with the cclimate change. However, increases in ignitions and vegetation continuity are independent of climate. The number of ignitions (both accidental and induced) is strongly related to human activity, and especially to urban activities in forested or semi-forested areas. The continuity of vegetation is mainly related to rural abandonment and dense forest plantations without proper management.
The increase of fires in Spain in the 1970s and 1980s is explained especially by the increase in vegetation continuity due to rural abandonment. Climate change played a minor role. As we allow climate change to advance, the relative role of climate in fires increases. It should be remembered that in Spain, and in many European countries, the forest mass is increasing, despite the fires.
Therefore, the increase in temperatures, heat waves and droughts greatly facilitates fires, but ignitions and continuous vegetation are also required. And that is good news. Reducing ignitions and generating discontinuities in vegetation is easier than reducing climate change (which is also necessary).
What can we do?
The policy of zero tolerance to fires has not worked in any country in the world. Not even in countries with very high firefighting budgets. Eliminating fires from our landscapes is impossible and counterproductive, especially in the context of climate change. We must accept a certain fire regime and learn to live with them.
The management challenge is to create conditions that generate ecologically and socially sustainable fire regimes. There is no simple or single recipe for achieving this. For example, it is not the same to manage an area where fires spread through the landscape mainly due to strong winds, than if they do so due to the existence of large homogeneous forest areas. In the first case, managing ignitions may be the most important thing. In the second case, fuel management may be the key.
Fires are especially dangerous when they approach semi-urban areas (in the wildland-urban interface) and this is where management is most important. One way to reduce fires is to generate discontinuities (horizontal and vertical) in the vegetation. There are several tools to do this, such as: cutting and prescribed burning, introducing herbivores (wild or livestock), alternating forest systems with crops, or allowing fires that are not very aggressive to burn. </p
Initiatives such as encouraging local rural activity andrewilding
can act in the right direction. Each of these tools may be valid depending on the site and conditions. And given the complexity of the issue, it may be important to explore a diversity of tools. None of them eliminate fires, but they reduce their likelihood, size, and intensity.
In times of heat waves or strong summer winds (e.g., during ponientes in Valencia) it would be important to limit human activities in the forest. That is, limit the passage of vehicles and people, including access to second homes located in forest environments. If during times of pandemic risk mobility has been limited, perhaps in times of maximum fire risk mobility in forest and semi-forest areas could also be limited. This is important because fires occur when ignitions coincide with adverse weather conditions in landscapes with sufficient vegetation. In such scenarios, reducing ignitions is key.
The wildland-urban interface could also be limited. That is, limiting the expansion of housing developments and industrial estates into rural and natural areas. This expansion, in addition to the well-known environmental effects (on biodiversity, invasive species, light and visual pollution, etc.), also constitutes a source of ignitions. Moreover, they put people and infrastructures at risk, and therefore make even ecologically sustainable fire regimes (socially) catastrophic. Mechanisms to limit these zones can be diverse, such as, for example, the rezoning of land (to undevelopable), or the implementation of fees (“pyrotaxes”) for building in areas with high fire risk. And urban planning needs to consider fires, including self-protection strategies around dwellings and the implementation of evacuation plans.
And in any case, fossil fuel consumption must be reduced. This would help to slow the increase in atmospheric CO₂, and thus reduce the speed of climate change and the frequency of heat waves. And not just because of fires.
**This article was originally published in The Conversation by Juli G. Pausas Researcher at the Consejo Superior de Investigaciones Científicas (CSIC), you can read it in full here.
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