The historical range of variability of fires in the Andean-Patagonian Nothofagus forest region

The present synthesis addresses key questions about several extreme fire events that occurred in the Nothofagus forest region of southern Argentina and Chile in the late 1990s and early 2000s: (1) are there historical precedents for the extent and severity of these recent wildfires? (2) To what extent can large, severe fires be attributed to influences from modern humans, either indirectly through land-use practices or directly through ignition? (3) What are the relationships of these fire events to interannual climatic variability and trends? (4) What are the medium-term ecological consequences of these fire events, particularly in terms of the resiliency of the burned ecosystems? Historic fire regimes vary greatly across the different ecosystem types in the southern Andean region, and the tree-ring record shows that before the 20th century, large severe fires also played a significant ecological role in shaping even the wettest forests. Recent severe droughts at an annual time scale have been facilitated by a trend towards higher temperatures since the mid-1970s. In large parts of the region, the risk of wildfire ignition and spread has been exacerbated by increases in lightning associated with higher temperatures, increased ignitions associated with exurban development, and conversion of less flammable native vegetation to more flammable plantations of exotic conifers.