Fig. 1

a Location of La Réunion island (credits Wikimedia Commons, the free media repository). b Map of Piton de la Fournaise showing the municipalities and towns (buildings are in black), roads (orange lines), trails (yellow lines), the vegetated areas (in green) and the location of the Enclos (blue line). The background is the hill shade of the lidar DEM from the Institut national de l’information géographique et forestière (IGN) – released in 2010, and coordinates are within system WGS84-UTM 40S. Buildings, roads, and trails are from BD TOPO® IGN. c Zoom of the Enclos and surrounding areas showing the lava flows from 1950 to 2021 (white to dark red). Lava flows that crossed the road are noted (grey arrow indicate flows that are now buried by more recent flows) and the Hors Enclos flows are highlighted with a yellow background