The destruction of tropical peatland forests is causing them to haemorrhage carbon dioxide into the atmosphere, scientists say.The destruction of tropical peatland forests is causing them to haemorrhage carbon dioxide into the atmosphere, scientists say.
The research, published in Nature, suggests peatland contributions to climate change have been badly underestimated.
'If you don't consider carbon lost through drainage then you underestimate the carbon losses from these deforested sites by 22 per cent,' says Dr Vincent Gauci of the Open University, one of the study's authors. 'And that's a conservative estimate; it could be much higher.'
Tropical peatlands have high water tables, starving them of oxygen and causing forest materials to rot more slowly. This allows them to build up vast stores of carbon tens of metres thick.
Most of it is found in the natural swamp forests of Indonesia, home to the endangered orang-utan, but more is being discovered across the tropics, particularly in South America.
Typically, estimates of carbon emissions from deforestation have focussed on the carbon lost from the trees themselves. The loss of carbon from the soil has been largely neglected until now.
'The effect of land use change has been underestimated,' says Gauci. 'The living trees are only a small component of the carbon held in these ecosystems.'
As the forest is cut down to make way for agriculture, often oil palms for use in biofuels, rainfall that would normally be used by the trees can drain through the peat, washing carbon away into streams and rivers.
'What's alarming is the radiocarbon dates. The stuff we measured that had drained through the peat column was thousands of years old, so it had been in storage for a long time', explains Gauci.
'Peatland should be absorbing and storing more carbon than it releases, but if you cut down the forest, that changes.'
And Gauci believes that the changing use of the land is at the heart of the problem.
'Using this type of land for biofuels will do more damage than good for the environment and climate change; it's completely wrong-headed,' he adds.
'The oil palm industry needs to be subject to regulation. It's an unsustainable use of the land.'
The study was led by Dr Sam Moore, an Open University PhD student funded by a Natural Environment Research Council (NERC) studentship.
It will contribute to the forthcoming Intergovernmental Panel on Climate Change assessment of the state of the Earth's climate.
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Moore, S. et al. Deep instability of deforested tropical peatlands revealed by fluvial organic carbon fluxes, Nature, 2013, doi:10.1038/nature11818