Connecting the dots: tracing the origins of 2015 equatorial Southeast Asian fires

Abstract

Tropical landscapes in Southeast Asia are susceptible to the detrimental consequences of fires. However, investigations on ignition sources in the region are limited despite its importance in formulating prevention strategies. We addressed this gap using a systems approach: a graph-theoretic method to identify the spatial origins of the devastating 2015 equatorial Southeast Asian fires. We then fitted a Random Forest model to explain the suitable conditions of fire origins using the identified origin points (n = 74 539–74 950) and predictors that comprised climatic, biophysical, and anthropogenic factors. We found that most fires in the region (∼84%) have multiple (>1) origin points. Overall, our modelling results conform to the anthropogenic origins of fires in the region, though geographical and climatic variables, such as ecoregion and long-term average vapour pressure deficit, act as major predictors of fire origins. The high importance of ecoregions in our model calls for ecoregion-based fire mitigation approaches. Incorporating ecoregion in our analyses has allowed for the identification of previously overlooked areas with high fire origin likelihood and areas potentially undergoing a major increase in fire origin likelihood following likely anthropogenic landscape modifications. Our identification of multi-origin fires in the region emphasises that preventing the expansion of areas with high fire origin likelihood is our best chance of preventing such resilient hazards.