Defining extreme wildfire events: difficulties, challenges, and impacts

Abstract

Every year worldwide some extraordinary wildfires occur, overwhelming suppressioncapabilities, causing substantial damages, and often resulting in fatalities. Given their increasingfrequency, there is a debate about how to address these wildfires with significant social impacts,but there is no agreement upon terminology to describe them. The concept of extreme wildfire event(EWE) has emerged to bring some coherence on this kind of events. It is increasingly used, often asa synonym of other terms related to wildfires of high intensity and size, but its definition remainselusive. The goal of this paper is to go beyond drawing on distinct disciplinary perspectives todevelop a holistic view of EWE as a social-ecological phenomenon. Based on literature review andusing a transdisciplinary approach, this paper proposes a definition of EWE as a process and anoutcome. Considering the lack of a consistent scale of gravity to leverage extreme wildfire eventssuch as in natural hazards (e.g., tornados, hurricanes and earthquakes) we present a proposal ofwildfire classification with seven categories based on measurable fire spread and behavior parametersand suppression difficulty. The categories 5 to 7 are labeled as EWE.