Reacción a "The rapid spread of extreme fires can lead to long-term changes in vegetation"

Often, what concerns the scientific community regarding global change is not (just) the scale of the changes, but the speed at which they are occurring. This applies to many processes, from the rate of species extinction to the accumulation of CO₂ in the atmosphere.

Indeed, in recent years (and weeks), during some particularly problematic episodes of forest fires, we have heard reports in the media of incidents where the fire is moving very quickly and spreading at abnormally high speeds. This is particularly worrying when those speaking about it are the people directly involved in firefighting, for obvious reasons.

A group of fire scientists, with extensive experience in analysing forest fires, their ecology and their impacts in North America, also focuses on speed in this study. In this case, they seek to identify relationships between the speed at which fires spread and some of their other characteristics (for example, their environmental effects). To this end, they have compiled data on nearly 3,500 fires that have occurred over more than a decade in the western and boreal regions of North America, in forested areas dominated by coniferous species. It is worth noting that this extensive study area generally includes territories where fire is, by nature, a key and frequent element in the functioning of ecosystems.

The dataset they use appears robust and encompasses a wide range of environmental conditions; however, despite this heterogeneity, the pattern of the results seems fairly consistent. Overall, they find a positive relationship between the rate of spread and the severity of the fire, which is a good measure of the fire’s impacts. In other words, fires that spread more rapidly are also, a priori, associated with more severe impacts.

Extreme-behaviour fires are becoming increasingly frequent across much of the planet and are even being observed in areas where they had never previously been recorded (or where they were very rare). They therefore constitute one of the main concerns of the scientific community. This is due both to their effects on society (for example, loss of life and material property) and to their impacts on ecosystems, their ecological functioning and their natural values. This study adds another piece to the puzzle of understanding these fires: it is not only the extent of the burn or the intensity of the fire that matters, but also the speed at which they spread, as all these variables are interrelated.