Burning peat bogs set alight by rainforest clearance in Indonesia are releasing up to a seventh of the world's total fossil fuel emissions in a single year, the geographers' conference heard.Tropical peatlands are one of the largest stores of carbon on the Earth's surface and setting them alight is contributing massively to global warming, said Dr Susan Page, senior lecturer in geography at Leicester University.
The carbon stored in the peat, formed by trees growing over 26,000 years ago, is 10 times greater than the carbon stored in the forest growing on top, making it a priority for the international community to stop them burning.
The peatlands burn each year during the dry season as farmers clear land, and once lit are hard to extinguish.
An area the size of Belgium has been cleared and burned in eight years, according to Dr Page.
At the current rate of burning the peatlands could be destroyed before 2040, she told the Royal Geographical Society's annual international conference in London.
Dr Page said: "This situation will only worsen. Although human-activated burning rates have slowed in the last three years, the cleared and dessicated soils are easily ignited during droughts. These occur naturally every three to seven years and will continue to make the problem worse for years to come."
Peatlands were burned on the orders of the former Indonesian dictator Suharto in an attempt to create one of the world's largest rice plantations. It has since been found that the acid soils are unsuitable for growing rice, making the Mega Rice Project one of the world's greatest environmental disasters and one that has led to air pollution as far away as peninsular Malaysia and Thailand.
"There have been some disastrous schemes - such as Saddam Hussein's drainage of the home of the Marsh Arabs in southern Iraq - but nothing on this scale," said Dr Page.
The Met Office's Hadley Centre for the study of climate change had predicted that the Amazon forest would begin to die back, accelerating the release of carbon and causing more climate change, if global average temperatures reached three degrees above pre-industrial levels.
Yadvinder Malhi, of Oxford's centre for the environment, said the forest was already changing, with faster growing trees increasing and slower growing trees declining - consistent with more carbon dioxide in the atmosphere and a rise in temperature of 0.5C.
"The threshold [for dieback] may be higher than we thought, but the forest that persists may be very different from today," he said.