In fall 2015, smoke from agricultural fires in Indonesia blanketed much of equatorial Asia. Schools and businesses closed, planes were grounded and tens of thousands of people sought treatment for respiratory illnesses.
In a new study, researchers estimate that the smoke caused upward of 100,000 deaths across Indonesia, Malaysia, and Singapore. The research is part of a larger effort to quickly identify fires in Southeast Asia that will have large impacts on human health downwind, and provide governments with tools that might be able to save lives. The study, coauthored by scientists at Harvard and Columbia universities, appears this week in the journal Environmental Research Letters.
“Although the regions experienced several major haze events over the past 20 years, the 2015 event was one of the worst,” said Harvard grad student Shannon N. Koplitz, the first author. “We understand many of the underlying conditions that lead to these extreme events, and we can often predict when smoke pollution will be severe based on particular meteorological indicators.”
Farmers in Indonesia, particularly those producing palm oil and timber for wood pulp and paper, are the main culprits in starting fires that cause haze events in this region. The fires, generally set in order to clear land, burn largely in coastal peatlands at relatively low temperatures. They can smolder for weeks or months before going out, resulting in large amounts of smoke.
During periods of extreme dry weather caused by the El Niño weather cycle and another cycle 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 fires are burning, they are more difficult to control. Although many fires burn in remote areas, 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 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, the researchers say.
“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, a Columbia University professor and coauthor of the paper.
Coauthor Jonathan Buonocore, a researcher at Harvard’s T.H. Chan School of Public Health, said, “We know for each incremental increase in air pollution, you get a certain incremental increase in mortality risk. 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.”
In ongoing work, the researchers are using their model to diagnose the health impacts of different land-use scenarios over the next 20 to 30 years. This effort could promote more rational land-use decisions as well as save lives, they say.
This is an adaptation of a press release from Harvard University.