Smoke from 2015 Indonesian fires may have caused more than 100,000 deaths

Fires started by farmers in Indonesia, particularly those producing palm oil and timber for wood pulp and paper, are the main culprits of haze events in this region. The fires, largely in coastal peatlands, burn at relatively low temperatures and can smolder for weeks or even months before extinguishing, resulting in lots of smoke. 

During periods of extreme dry weather caused by El Niño and a phenomenon called the positive Indian Ocean Dipole, smoke emissions are considerably higher — either because farmers are taking advantage of the dry weather to burn more land or because once burning, the fires are more difficult to control. Although many fires burn in remote areas of Indonesia, prevailing winds can carry the smoke hundreds of miles to densely populated cities like Palembang in Sumatra, and Singapore and Kuala Lumpur. 

The region experienced similar smoke conditions caused by El Niño in 2006 but the Harvard-led team found that deaths from air pollution more than doubled between the 2006 and 2015 events, from about 38,000 to about 100,000. This is largely because of where the fires burned in relation to population centers, and their intensity. Fires in southern Sumatra and nearby Jambi province turn out to be particularly deadly. 

“Based on years of epidemiological research, we understand very well the relationship between pollution and mortality,” said Jonathan Buonocore, coauthor and research associate at the T. H. Chan School of Public Health. “We know for each incremental increase in air pollution, you get a certain incremental increase in mortality risk.”

Being able to identify the most dangerous fires could help save lives in the future, Buonocore said. “For the first time in Indonesia, we have a rapid assessment modeling tool that can quickly estimate the cost to human health of these haze events, as they are happening,” he said. 

Harvard notes that in ongoing work, the researchers are using the model to diagnose the health impacts of different land-use scenarios over the next 20-30 years. This effort could promote more rational land-use decisions and management that could save thousands of lives.

“If regional policy makers understand fully the health dimension of these biomass fires, we believe they will be in a better position to manage them more effectively and improve human health and ecosystems at the same time,” said Ruth DeFries, of Columbia University and coauthor of the paper.

— Read more in Shannon N Koplitz et al., “Public health impacts of the severe haze in Equatorial Asia in September–October 2015: demonstration of a new framework for informing fire management strategies to reduce downwind smoke exposure,” Environmental Research Letters 11, no. 9 (19 September 2016): 094023 (DOI: 10.1088/1748-9326/11/9/094023)