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Exponential link between fires and drought

Firefighting in peatland near Palangkaraya, Central Kalimantan. Photo by Charlie Pye-Smith

In recent years parts of Southeast Asia have been regularly blanketed in an atmospheric haze, sometimes for months at a time. Most of it comes from the setting of fires to clear vegetation in Indonesia, Malaysia and Papua New Guinea.

Emissions from the fires are problematic. In extreme cases, they can cause respiratory and other health problems. They can affect transportation by forcing airports to close. The fires also release enormous amounts of carbon into the atmosphere, contributing to global warming and climate change.

According to a recent report, ‘Climate regulation of fire emissions and deforestation in equatorial Asia’, published by the US National Academy of Sciences, the intensity and frequency of these fires appears to be increasing. One of the report’s co-authors, CIFOR scientist Dr Daniel Murdiyarso, said the research team had always assumed the amount of fire activity would be much greater during periods of drought. But what surprised the scientists was the size of the increase in fire emissions in relation to the severity of the drought.

‘The relationship was exponential. The increases in fires and emissions were much more than could be explained in terms of the severity of the drought alone,’ said Murdiyarso. ‘Other factors must have been involved. It’s not surprising that some of these were human factors.’

Their results suggest an increase in the severity of the drought allows for faster land-clearing rates. Faster clearing rates in turn make accidental fires more likely. Conversely, if the dry season is not as dry as normal, peatland, scrub and forest are less flammable.

These observations, said Murdiyarso, point towards ‘a strong coupling between climate variability and human land management’ and could have significant implications for any future global climate change agreement.

You can find the full report, 'Climate regulation of fire emissions and deforestation in equatorial Asia', at 
http://www.pnas.org/content/105/51/20350