Wildfires in Indonesia made a major contribution to the highest atmospheric carbon dioxide (CO₂) concentrations ever recorded in a single year, according to new calculations reported by Susan Page of the University of Leicester in the United Kingdom, and colleagues. The researchers estimate that during the unusually long El Niño dry season of 1997, smoldering peat swamp forests in Borneo released as much as 2.6 billion tonnes of carbon, mostly as CO₂, which equates to about 40% of the mean annual global emissions from fossil fuels.

Tropical peatlands store significant amounts of carbon, and therefore their destruction has important implications for climate change. In the 1997 wildfires, about 33% of Indonesia’s peat bogs were lost. To determine how much carbon was actually released, the researchers used peat thickness, prefire land cover, and burnt area land data. Using satellite images, they established the composition of land cover over a 2.5 million-hectare area in Central Kalimantan, Borneo.

In addition, the researchers discovered a 44% increase in logging activities between 1997 and 2000, which disturbed the waterlogged peatlands and made the remaining forests more susceptible to fire. Although peatlands comprise only a small area of the globe, the researchers believe that disturbing bogs will continue to make a significant contribution to global carbon emissions, unless efforts are made to prevent further destruction of them. (Nature 2002, 420, 61–66)