Validating a landscape metric to map fire exposure to hazardous fuels in Portugal

Assessing wildfire hazard at the landscape level in Portugal with low-cost and time-saving methods is necessary to guide land and fire managers and protect communities at risk. This study applied a landscape metric developed in Canada to map wildfire exposure in Mainland Portugal between 1995 and 2018. The wildfire exposure metric was computed and validated by examining exposure within subsequently burned areas over five years: 1995, 2007, 2010, 2015, and 2018. Landscape fire exposure was computed by the proportion of neighborhood cells in a 100 m resolution grid that include hazardous fuel types. The resultant exposure metric analyzes the amount of land cover type in the area of a site that will either aid or prevent fire spread. The distribution of exposure levels remained relatively stable over time, decreasing just 0.5% from 1995 to 2018. Approximately 80% of burned areas occurred in sites with substantial exposure (i.e., ≥ 80%). This exposure metric, originally developed in Canada, aligned well with wildfires modulated by Portuguese climate and vegetation, leading to its successful validation. This study uses a simple, time-saving method to show high and low wildfire exposure areas, allowing managers to plan mitigation efforts at different scales, with potential applications for other countries facing large wildfire events.