Where Fire Crosses Borders: Extent, Spread Direction and Joint-Attention Zones of Transboundary Fires in Central South America (2012–2025)

Fires crossing international borders challenge nationally organised fire management, yet remain poorly quantified in South America. We combined national MapBiomas Fire burned-area maps for Argentina, Bolivia, Brazil, Colombia, Paraguay and Peru with VIIRS/MODIS active fires and MapBiomas land cover to delineate and characterise transboundary fire events along 14,934 km of borders between 2012 and 2025. We identified 360 events covering 9.23 Mha. The Bolivia–Brazil border concentrated 73.3% of the burned area, followed by Bolivia–Paraguay (15.0%), Brazil–Paraguay (7.4%) and Argentina–Paraguay (4.2%). Three years (2024, 2019, 2020) accounted for 70.8% of the area and the 52 events ≥10,000 ha for 97.6%. Of the 278 events with active fires, 84 showed a directed border crossing; these accounted for 73.7% of the burned area, were balanced between neighbouring countries and crossed a median of 2.5 days after ignition. Natural vegetation made up 94.0% of the burned area, whereas farmland hosted 18.7% of ignition points. Ranking 25-km border segments by recurrence, burned area and crossings identified 18 joint-attention zones, led by the southern Pantanal, that hold 76.1% of the burned area in the border strip on 6% of the border length. These results provide an empirical basis for binational fire management.