Thursday, September 16

Forest fires: not everything is climate change

In these days of heat waves, big fires are taking place in the Mediterranean, especially in Turkey, Greece and Italy. Similar situations are occurring in other parts of the world (California, Siberia, etc.). And something similar we lived last summer. Therefore, it is understood that, repeatedly, they ask me if all these fires are a consequence of climate change.

The short answer is that climate change facilitates fires (favors the spread of fire and extends the fire season), but does not mean that there are fires. I try to answer in more detail below.

The ingredients

For fires to break out, at least three ingredients, which must also be given 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 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 (triggers).

When the three thresholds are exceeded, megafires that are difficult to control are generated. And these thresholds vary with weather conditions. Specifically, they are very low when temperatures are especially high (heat waves), low humidity or strong winds. In other words, under these conditions, it takes less ignition, less fuel, and less drought to start fires. Therefore, in those particular conditions fires are much more likely, as long as there are ignitions and continuity of the fuel.

The recent increase in droughts and heat waves is associated with the climate change. However, increases in ignition and vegetation continuity are independent of climate. The number of ignitions (both accidental and provoked) is closely related to human activity, and especially to urban activities in forest or semi-forest areas. The continuity of the vegetation is mainly related to rural abandonment and dense forest plantations without proper management.

The increase in fires in Spain in the 70s and 80s is explained especially by the increase in continuity of vegetation due to rural abandonment. Climate change played a minor role. As we let climate change unfold, the relative role of weather in fires increases. It must be remembered that in Spain, and in many European countries, the forest mass is increasing, despite the fires.

Therefore, increasing temperatures, heat waves and droughts greatly facilitate fires, but ignitions and continuous vegetation are also required. And that’s good news. Reducing ignitions and generating discontinuities in vegetation is easier than reducing climate change (which is also necessary).

What can we do?

The zero tolerance policy for fires has not worked in any country in the world. Not in countries with very high dying 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. To achieve this there is no simple or unique recipe. For instance, It is not the same to manage an area where fires spread through the landscape mainly thanks to strong winds, as if they do so due to the existence of large homogeneous forest extensions. In the first case, managing the ignitions may be the most important thing. In the second, the key may be to manage fuel.

Fires are especially dangerous when they approach semi-urban areas (at the urban-forest 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 various tools for this, such as: carrying out prescribed cutting and burning, introducing herbivores (wild or livestock), alternating forest systems with crops, or allow fires that are not very aggressive to burn.

Initiatives such as incentivizing local rural activity and the resilience (rewilding) they can act in the right direction. Each of these tools can be valid depending on the site and conditions. And given the complexity of the topic, it may be important to explore a variety of tools. None of them eliminate fires, but they reduce their probability, their size, and their intensity.

In times of heat waves or strong summer winds (for example, during the west in Valencia) it would be important to limit human activities in the mountains. That is, limit the passage of vehicles and people, including access to second homes located in forest environments. If mobility has been limited during times of pandemic risk, perhaps at 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 those scenarios, reducing ignitions is key.

The urban-forest interface could also be limited. In other words, limit the expansion of urbanizations and industrial estates in rural and natural areas. This expansion, in addition to the well-known environmental effects (on biodiversity, invasive species, light and visual pollution, etc.), also constitute a source of ignitions. Furthermore, they put people and infrastructure at risk, and thus make even ecologically sustainable fire regimes catastrophic (socially). The mechanisms to limit these zones can be diverse, such as, for example, the requalification of land (to non-developable), or the implementation of fees (“pirotasas”) for building in areas with a high risk of fires. And urban planning requires considering fires, including self-protection strategies around homes and the implementation of evacuation plans.

And in any case, we must reduce the consumption of fossil fuels. This would help to slow down increasing atmospheric CO₂, thereby reducing the speed of climate change and the frequency of heat waves. And not just because of the fires.

** This article was originally published on The Conversation by Juli G. Pauses Researcher at the Higher Council for Scientific Research (CSIC), you can read it in full here.