Weather impacts on fire thresholds: Recipe for big fire

View brief.

Large wildfires need four key ingredients to burn, not just one. Ignitions, fuels, and drought thresholds must be crossed at the same time, enhanced by anomalous weather events such as foehn winds. But how do these ingredients, or drivers, fit together in various ecosystems? In this important concept paper, Pausas and Keeley (2021) outline the mechanistic flow of these complex drivers for fire prone ecosystems and illustrate this in the figure below (Fig.1). In brief, the fire weather for a given ecosystem helps to push the other three essential driver thresholds, or saturation points, down. With ignitions, fuel continuity, and drought saturation points simultaneously lowered by the right weather, wildfire will be triggered.