Researchers at the University of Leeds and the University of London have realised the full extent of the Cuvette Centrale, a remote peatland in the Congo basin. Unknown to science five years ago, the peat soils have been found to take up 145,500 square kilometres – larger than the size of England – making it the largest peatland under tropical forest in the world.

According to the report, the soils have locked in 30 billion tonnes of carbon, about 20 years’ worth of the fossil fuel emissions of the United States (or three years’ worth of the entire planet’s). Overall, the area is thought to account for 30 per cent of the carbon stored in tropical peatlands. ‘Although it covers only four per cent of the whole Congo Basin, it can store the same amount of carbon below ground as that stored above ground in the trees covering the other 96 per cent,’ says Professor Simon Lewis, co-author of the study.

Map detailing the size and spread of the Cuvette Centrale peatlands (Image: Lewis et al)

The area was mapped using satellite data. Though satellites cannot tell you much about the soil under the land, they can observe the types of plants on top of it. The team found through measurements in the field that only two specific types of forests grow over peatland. By looking for those types of vegetation in the satellite data, the researchers were able to determine the surface area. By collecting core samples of the soil , they were then able to calculate the peatland’s depth as well as its carbon storing capacity.

Though they only cover around three per cent of the Earth’s surface, peatlands store between one third and half of all the carbon absorbed by soils. Usually found in cold, damp regions such as Russia, Canada and northern Europe, their overlying plants absorb CO₂ through the air, which then becomes locked in as they decompose. It is thought that the Cuvette Centrale began storing its load 11,000 years ago.

Part of a carbon core sample (Image: Lewis et al)

While healthy peatlands are a sink of carbon, disturbed or damaged peat can become a source. In Indonesia, for example, draining, drying and, in some cases, setting fire to the soil has resulted in large injections of carbon dioxide into the atmosphere. ‘With so many of the world’s tropical peatlands under threat from land development and the need to reduce carbon emissions to zero over the coming decades, it is essential that the Congo Basin peatlands remain intact,’ says Lewis.

Being remote, the Cuvette Centrale area is relatively undisturbed. However, it does not yet come under any formal agreement for conservation.