A vast and remote expanse of peat swamp forest in the Congo Basin, Central Africa, is far older than previously thought, according to a new study.
Led by scientists from the University of Leeds, the work reveals that the world’s largest tropical peatlands began forming more than 42,000 years ago – over twice as long ago as previous estimates suggested.
The discovery highlights the long-term importance of the Congo peatlands as one of the most vital carbon stores on Earth, say researchers, who published their findings in the journal Environmental Research Letters.
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Beneath the surface
Peat is a dense, wet soil made of dead plant matter. It builds up slowly in waterlogged environments, locking away carbon that would otherwise contribute to climate change.
While the Congo's lush forests are well known for storing carbon in their trees and vegetation, recent research has shown that just as much carbon lies hidden beneath the surface in the peat itself.
“These peat swamp forests are a globally important carbon store, holding the equivalent of three years of global fossil fuel emissions,” says Dr Greta Dargie, lead author of the study from the University of Leeds. “We now know that they are among the most ancient tropical peatlands on the planet.”
Into the swamp forest
The study was based on fieldwork that spanned more than a decade. Teams of researchers travelled deep into the swampy forests of both the Republic of the Congo and the Democratic Republic of the Congo, collecting samples of peat using hand tools. Some samples came from as deep as six metres below the forest floor.
Using radiocarbon dating, the scientists determined how long the peat had been accumulating. By analysing more than 50 cores from across the central Congo Basin, they built a timeline of how these tropical wetlands have developed over tens of thousands of years.
One of the biggest surprises, explains Professor Ifo Suspense of the University of Marien Ngouabi, in Brazzaville, was the discovery that “some of the older peatlands in central Congo Basin began forming during periods of the past when we think that the regional climate was a lot drier than it is today.
“This raises questions about how the peatland landscape, and the large amount of carbon it stores, will respond to 21st century climate change.”
Growing threats
The Congo Basin peatlands are not just important for the climate – they are also home to rare and endangered wildlife, including lowland gorillas, forest elephants, dwarf crocodiles and bonobos. Local communities rely on the swamps for fish, bushmeat and other natural resources.
Until now, these peatlands have remained mostly untouched by threats such as drainage and deforestation, thanks to their inaccessibility. But growing pressure to extract timber and oil, and to develop infrastructure, could put both biodiversity and the ancient carbon stores at risk.
“The peat can’t be replaced on any timescale that’s meaningful to society,” says co-author Dr Pauline Gulliver from the University of Glasgow.
“Where peatlands have been disturbed by people around the planet, they have released huge amounts of carbon to the atmosphere, exacerbating global warming.
“The carbon in the Congo Basin peatlands requires careful treatment so that the same thing does not happen here,” Gulliver concludes.
Find out more about the study: Timing of peat initiation across the central Congo Basin
Top image: Swamp forest in Democratic Republic of Congo. Credit: Greta Dargie
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