An improved mapping of burned areas in Alto Minho (Northwest Portugal) between 2001 and 2020

Abstract

Alto Minho is a region of northern Portugal in the northwest of the Iberian Peninsula, which is one of the regions in Europe where fires are more frequent. The historical mapping of burned areas has been fundamental to characterize the fire regime and to determine wildfire prevention policies and urban planning measures. Over the last decades, several studies have been published seeking to characterize the impact of fire on the territory, its frequency and recurrence, based on the official cartography, provided by the Instituto de Conservação da Natureza e das Florestas – ICNF. In this study, a detailed and rigorous cartography of the areas affected by fires in the Alto Minho area in the last two decades (2001 to 2020) was developed. These areas were determined based on the analysis of 400 images from the Landsat 5 (TM), Landsat 7 (ETM+), Landsat 8 (Operational Land Imager – OLI) and Sentinel-2 (Multispectral Instrument – MSI) satellites, whose perimeters resulted from manual digitizing supported by historical series of orthophotos. A total of 12 692 fire perimeters were digitalized corresponding to 235 060 hectares of burned area in the Alto Minho region. These results substantially differ from the official cartographic information, in terms of cartographic accuracy, number of fire perimeters (3873) and burned area (179 283 hectares).