Preprint for "The properties of individual fire events are essential for understanding global fire regimes"

Adam Lee Mahood , Maxwell Cook, Ty Tuff, Natasha Stavros, Amy DeCastro, Chelsea Nagy, Megan Cattau, David Barnard, Virginia Iglesias, Jilmarie Stephens, Jennifer Balch, Thomas Hanson

Aim: As fire activity changes globally, we need to better understand the spatial and temporal characteristics of the individual events that, when aggregated, constitute fire regimes. Most global studies analyze point detections of burned area, without delineating or considering the properties of individual events. Furthermore, there is a critical need to understand fire patterns within the context of the geopolitical boundaries within which fires are managed. Location: Global Time period: 2003-2020 Major taxa studied: Fire Methods: We divided 241 countries by Köppen-Geiger climate classifications and quantified four event-based fire regime metrics: size, duration, and mean and maximum growth rate; and four area-based metrics: burned area, number of fires, season length, and season peak. We examined the correlations among fire regime components, and between each fire regime component and climate normals. We quantified temporal trends, and used mixed models to analyze how climate and landcover change were associated with event-based components of fire regimes. Results: Event-based metrics were weakly correlated with area-based metrics. Countries with warmer and less variable climates had high burned area, more fire events, longer season lengths and shorter event durations. Countries with high annual temperature range and low precipitation tended to have fewer events but larger fires that were faster-spreading and occurred later in the year. The growth rate and size of individual fire events are increasing in 18% and 21% of regions we analyzed, respectively. Interannual variability in size and growth rate were associated with aridity increases in boreal areas, and landcover changes in arid areas. Main Conclusions: Drivers of burned area and fire seasonality are well-understood but largely unrelated to the properties of individual events. A more detailed understanding of the spatial and temporal aspects of fire events at broad scales will assist fire management efforts in preparing for a warmer future.