"Previous work has focused on changes in carbon stocks among different concession types, but not differences in fire activity," Miriam Marlier of Columbia University told environmentalresearchweb. "Our results support previous findings that deforestation typically stays low in logging concessions, while highlighting the risk of fires in timber (for wood pulp and paper) and oil palm concessions. However, the impacts of different concession types on regional air quality has not previously been examined."

Fire is seen as a cheap and effective way to clear and maintain land for agricultural and plantation development, according to the researchers. In total, concessions for the oil palm, timber and logging industries cover 21% of Sumatra’s land area and 49% of Kalimantan. In Sumatra, concessions contributed 41% of total fire emissions for 2006, whilst in Kalimantan the figure was 27%. Most of these contributions came from concessions on peatlands and non-forested lowlands, the team found.

"Our results suggest the importance of limiting the use of fire by the oil palm and timber industries, especially in concessions on carbon-rich peatlands and non-forested areas that are highly susceptible to burning," said Marlier. "Limiting the reclassification of logging concessions to other concession types would help to protect public health in the absence of limiting fires in timber and oil palm concessions."

Timber and oil palm concessions were stronger contributors to fire emissions than logging concessions, the team confirmed. The timber industry creates plantations of fast-growing trees, whilst logging takes timber selectively from natural forests. In Kalimantan 65% of the fire emissions from all concessions between July and November 2006 were due to oil palm concessions and 26% were due to timber. In Sumatra, meanwhile, 86% of these emissions came from the timber industry and 13% from the oil palm industry.

Not only do fires affect biodiversity and ecosystem services, but they also release emissions that harm air quality and contribute to greenhouse gas levels. The year 2006 saw a particularly high incidence of forest fire in Indonesia; concession fires on Sumatra from July to November 2006 produced 79 Tg of dry matter, whilst those on Kalimantan produced 91 Tg. The resulting smoke and haze affected many countries across southeast Asia, including Malaysia, Thailand and Singapore.

"By combining satellite observations of land cover and fire activity with atmospheric modeling techniques, we were able to extend our analysis to compare the effects of fires associated with industrial concessions on regional air quality," said Marlier. "Given the proximity to population centres like Singapore, fire emissions from Sumatra impact smoke concentrations there more than Kalimantan, despite having lower emissions."

Methods for limiting the use of fire by the timber and oil palm industries include better monitoring systems, local-level management, and enforcement of existing fire bans.

"Our ongoing research involves understanding the sensitivity of our results to interannual climate variability and estimating the public health costs of air quality degradation from fires in industrial concessions," said Marlier.

Marlier and colleagues reported their work in Environmental Research Letters (ERL).

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