In 1997-98, extremely dry El Niño conditions in Indonesia kicked off a wave of large–scale uncontrolled burning, destroying about five million hectares of tropical forest (equivalent to seven million football fields). Much of the burning occurred in carbon-rich peatland forests and continued in two phases from July 1997 until March 1998, releasing vast amounts of carbon dioxide into the atmosphere, and huge clouds of smoke and haze across the region.
Present conditions in the Pacific Ocean are similar to what they were in mid-1997. El Niño is set to strengthen, and seasonal weather prediction models point towards this being an exceptionally dry season. Indonesia and its neighbours should be worried.
In order to predict, and hopefully prevent, such fires in the future, we’ve looked at how far in advance they can be anticipated using a seasonal weather prediction model.
Deforestation, Peat Drainage and El Niño
During the dry season, numerous fires occur in Indonesia’s peatland forests, particularly in the southern region of Kalimantan and eastern Sumatra. Although some rain falls during a normal dry season, it is sporadic, leaving many windows of opportunity for burning.
Most of these fires are deliberately lit to clear rainforest to establish oil palm and Acacia pulp and paper plantations. Fire spread is enhanced by the increased availability of combustible material, notably, woody debris as a result of wasteful logging practices, and the widespread practice of draining peatlands.
When El Niño strikes, however, the situation changes drastically. During strong El Niño episodes, almost no rain falls during the dry season and the monsoon is delayed. So in areas where peatlands have been degraded by logging and draining, fires ignite easily and once started, the peat is so dry that fires escape underground, and cannot be put out until after the monsoon reappears.
At their worst, the fires have enormous impacts on carbon emissions, regional haze production, biodiversity, and the economy, and are recognised as a serious health risk in Indonesia as well as neighbouring Singapore and Malaysia. The fires are a major threat to the remaining orangutans who live in the forests – the Bornean orangutan is rated endangered, and the Sumatran orangutan is critically endangered. During past El Niño years, around one gigatonne of carbon was emitted from peatland forest fires, equivalent to about 10% of annual global fossil fuel emissions, and regional haze from such fires has caused major disruptions to air traffic in nearby Singapore and Kuala Lumpur.
