Connecting the dots behind Southeast Asia's catastrophic fires

The devastating fires that swept across equatorial Southeast Asia in 2015 burned millions of hectares of land, blanketed the region in haze, and caused widespread environmental, health, and economic impacts. Despite their scale, relatively little is known about where these fires begin and the environmental and human factors associated with their origins.

The authors of a new study published in Environmental Research Letters aimed to address this gap. Using the 2015 fires as a case study, the researchers applied network analysis of satellite observations to trace fire origins and examine the regional natural and human factors associated with them. The approach enabled the team to identify approximately 74,500–75,000 fire origin points across nearly 15,000 fire networks.

One of the study's clearest findings is that the larger the fires, the more likely they are to have many origins. Around 84% of the fire networks analyzed had multiple origin points, suggesting that many of the region's largest fires developed when multiple independently originating fires expanded and merged.

The researchers also found that the conditions associated with where fires begin are shaped by a combination of natural and human influences. Among the factors examined, the type of natural landscape where a fire occurs (known as an ecoregion) and atmospheric dryness were the strongest predictors of fire origins. The findings expand previous evidence that most fires in the region are linked to human activities by highlighting the important role of environmental conditions in determining where fires are most likely to originate.

“Atmospheric dryness will increase with climate change, which will consequently increase risks of fire. This finding could potentially challenge the current understanding that Southeast Asian tropical forests could recover from natural disturbances due to the amount of rainfall,” explains coauthor Ping Yowargana, Senior Research Scholar at IIASA.

"Our results show that the causes of fires are not just complicated, but also dynamic," adds lead author Adrian Dwiputra, a researcher at the National University of Singapore (NUS) and in the Agriculture, Forestry, and Ecosystem Services Research Group of the IIASA Biodiversity and Natural Resources Program. "Among the many factors that contribute to fire hazards, human links are more dominant among origin points, while natural links contribute more significantly among spread points. Complex problems require complex understanding and complex solutions. Abductive simplifications can be misleading when applied to study complex and resilient socioecological hazards, such as fires. For these topics, we may be required to connect the hidden dots in both figurative and literal ways."

The results provide new insights for fire prevention. By taking different natural landscape types into account the results, for example, reveal higher fire-origin likelihood in areas such as the Borneo rainforest, surpassing that of established hotspots like the Borneo peat swamp forest. Because many large fires begin at multiple locations before merging, the authors suggest that preventing the expansion of areas where fires are likely to originate could help reduce the likelihood of future catastrophic fires.

The research could benefit people managing fire-prone landscapes including field practitioners and policymakers, as well as scientists developing models to better understand fire risk, improve prevention and suppression, and assess the long-term ecological impacts of fires.

Reference
Dwiputra, A., Yowargana, P., Lee, J.S.H., Teo, H.C., Tan, Z.D., Zeng, Y., Krasovskiy, A., & Koh, L.P. (2026). Connecting the dots: tracing the origins of 2015 equatorial Southeast Asian fires. Environmental Research Letters DOI: 10.1088/1748-9326/ae81ca