The recent surge in levels of atmospheric carbon dioxide, which made front-page headlines around the world last month, may have been caused in part by smouldering peat bogs in Borneo.
This is the claim of a UK expert on the bogs, who says that further fires will accelerate global warming. Burning peat could be a major contributor to the as yet unexplained accelerating build-up of CO2 in the atmosphere since 1998, says Jack Rieley of the University of Nottingham in the UK. His warning comes as peat bogs in Indonesia began burning again last month.
Atmospheric concentrations of CO2, the gas primarily responsible for climate change, have been rising since records began in 1958. The rate of increase has risen from around 0.8 parts per million (ppm) per year in the 1960s to around 1.5 ppm per year in the 1990s.
Since 2000 the pace has accelerated further, with year-on-year rises of 2.1 and 2.5 ppm peaking with an increase of 3.01 ppm in the 12 months ending in August 2003 (New Scientist print edition, 9 October).
There have been surges before. There were increases of 2.2 ppm in 1973, 2.5 ppm in 1987 and 2.9 ppm in 1998. But they have been restricted to single years and all coincided with the climate anomaly El Niño. The most recent is puzzling both because of its length and because it occurred in the absence of a strong El Niño.
Sinks to sources
Rieleys theory offers a possible explanation. He points out that the surge coincides with peat fires burning in Borneo since late 2002, and says this renewed burning is at least partly responsible for the new CO2 record. Tropical peatlands are rapidly being converted from carbon sinks to carbon sources, he says.
The peat bogs of Borneo and the neighbouring territories of Sumatra and Irian Jaya are up to 20 metres deep and cover more than 200,000 square kilometres. They contain 50 billion tonnes or more of carbon far more than the forests above. As farmers clear the forests by burning, the bogs catch fire and release carbon for months afterwards.
In 2002, Rieley and his colleagues estimated that during 1997 and 1998 smouldering peat beneath the Borneo forests released between 0.8 and 2.6 billion tonnes of carbon into the atmosphere. That is equivalent to 13 to 40 per cent of all emissions from burning fossil fuels, and contributed to the CO2 peak in 1998.
A biologist from Borneo told New Scientist this week that the fires have now returned. During October, the atmosphere around Palangka Raya has been covered in thick smoke, with visibility down to 100 metres. The schools have been shut and flights cancelled, says Suwido Limin from the University of Palangka Raya in the Indonesian province of CentralKalimantan.