Scientists have mapped what they say is the largest peatland in the tropics, an area larger than New York State in the Congo Basin in Central Africa.
The peat, which consists of slowly decomposing vegetation in swamp forests, has been accumulating for more than 10,000 years. As in all peatlands, the vegetation is a natural storehouse of carbon taken from the atmosphere — in this case, about 30 billion metric tons of carbon, or roughly equivalent to the carbon in two decades of fossil fuel emissions in the United States.
“It’s astonishing to me that in 2017 we can be making these kinds of discoveries,” said Simon Lewis, a professor at the University of Leeds in England and an author of a study on the peatlands being published on Wednesday in the journal Nature.
Dr. Lewis and his colleagues first discovered the peatlands several years ago, working on a hunch that in the wetlands known as the Cuvette Centrale, which straddle the border of the Republic of Congo and the Democratic Republic of Congo, they would find peat in layers under the swamps. The vegetation, which is waterlogged year-round, lacks oxygen and other nutrients that would lead to its quick decomposition.
The current study used satellite imaging and analysis to determine the extent of the peat, which is about 55,000 square miles. Field work across the wetlands — which Dr. Lewis said were the most difficult expeditions he had undertaken in 15 years of research in Africa — revealed the depth of the peat, up to 20 feet, allowing a calculation of the amount of stored carbon.
Peat covers only about 3 percent of Earth’s land surface, but because it stores carbon over a long time, it contains as much carbon as all of the world’s plants and trees, and almost as much as the atmosphere.
Most peatlands are in northern regions, including Alaska, Canada and Russia. But tropical peatlands, especially, are highly vulnerable to land-use changes and climate warming, both of which can lead to the peat drying out and decomposing quickly, which would release the carbon back into the atmosphere.
Vast tracts of peat in Indonesia, for instance, have been drained for oil-palm production, leading to fires and rapid carbon release. In the fall of 2015, Indonesia peat fires released more carbon per day than the European Union.
The Congo Basin peatlands are in a relatively inaccessible area and are largely undisturbed. But scientists and environmentalists fear that the same kinds of pressures affecting Indonesia could eventually affect the Cuvette Centrale peatlands, which store about 30 percent of the carbon found in tropical peatlands worldwide.
Emma J. Stokes, who directs the Central Africa program for the Wildlife Conservation Society, said that protecting the peatlands was crucial, as the swamp forests that overlie them are home to many animals, including some of the highest densities of lowland gorillas anywhere.
The area’s inaccessibility was “one of the reasons it’s been afforded natural protections over the years,” said Dr. Stokes, who was not involved in the study.
“But I don’t think we can sit back and relax and say that everything’s going to be fine,” she said. “We definitely need to be proactive in avoiding any kind of land-use decisions that will risk impacting on these forests and peatlands.”