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A peatland complex in the Congo Basin which is known to be a globally important carbon store is twice as old as previously thought, according to a new scientific study supported by expertise from the Â鶹ÊÓƵ.

An international team of researchers has shown that the tropical peatland complex, which is the world’s largest, began forming about 42,000 years ago, more than 20,000 years earlier than previously thought. 

Peat is a type of soil that forms in wet environments. Made up of dead plant litter, it is an important part of the carbon cycle. While it is well known that the Congo Basin’s forests store a lot of carbon in the biomass of the living plants, work over the past decade has shown that Congo Basin peatlands store a similar amount of carbon out of sight below ground. This realisation has revolutionised scientific understandings of the importance of the region for the global carbon cycle. 

Professor Sue Page MBE, from the Â鶹ÊÓƵ School of Geography, Geology and the Environment, said: "Research undertaken as part of the CongoPeat project continues to provide us with surprising insights into not only the extent of tropical peatlands and the size of their carbon stores, but also the age of their formation. Prior to the dating of these peat samples, we had assumed that the Congo Basin peatlands were likely less than 20,000 years old.  But our results described in this paper indicate that these peatlands have been in existence for a much longer period - around 45,000 years - and that over most of this long time period they have been acting as an important carbon sink, sequestering carbon dioxide from the atmosphere and locking it away in waterlogged peat. These findings emphasis the vital role that peatlands play in climate regulation, in this case over many millennia, and further strengthen the need for their protection."

Geochemist on the Congo Peat project Dr Arnoud Boom, from the Â鶹ÊÓƵ, said: “It is remarkable that some peatlands in the Congo Basin date back well before the Last Glacial Maximum. Yet despite this apparent resilience, these ecosystems are highly sensitive to contemporary climate change, and the risk of losing large amounts of stored carbon is very real.”

The new study published this week in the scientific journal Environmental Research Letters began with teams of scientists trekking through remote and inaccessible peat swamps in both the Republic of Congo and the Democratic Republic of the Congo, using hand-operated equipment to collect samples of the peat from up to six metres below the forest floor.  

Back in the laboratory, tiny amounts of the peat were dated using radiocarbon, to determine when the peat began to form in each sampled location. Over a period of 10 years the scientists collected and dated more than 50 cores from across the central Congo Basin, from which they were able to build up a picture of the development of the peatlands through time.

of the University of Leeds, School of Geography, led the study. She said: “These peat swamp forests are a globally important carbon store, holding the equivalent of three years of global fossil fuel emissions. We now know that they are among the most ancient tropical peatlands on the planet.”

It is not just the great age of the peatlands which came as a surprise to the scientists. Professor Ifo Suspense from the University of Marien Ngouabi, Brazzaville, in the Republic of the Congo, said: “One of the most unexpected findings which came from our new data is 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.  

“Our previous working hypothesis was that the peat began forming in response to a wetter climate at the start of the Holocene epoch, around 12,000 years ago. But we now know that factors other than climate must have made the soils wet and waterlogged enough for peat to form. This raises questions about how the peatland landscape, and the large amount of carbon it stores, will respond to 21st century climate change.” 

The Congo Basin peat swamps provide important resources for local communities such as fish, bushmeat and building resources. Their remoteness means that the swamps are important refuges for species such as forest elephants, dwarf crocodiles, lowland gorillas and bonobo chimpanzees.  

Compared to many tropical regions, the Congolese peatlands have largely escaped threats such as deforestation and drainage, although the drive to improve local livelihoods and extract resources such as timber and oil for export could potentially come into conflict with the goals of biodiversity and carbon conservation. 

“There has been peat here, quietly drawing carbon out of the atmosphere, and safely storing it for at least forty millennia. The peat can’t be replaced on any timescale that’s meaningful to society.  

“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.”

• is published in the journal Environmental Research Letters
• The work was lead from the University of Leeds, in collaboration with Aix Marseille University, France, Christian-Albrechts-Universitaet zu Kiel, Germany, L'Institut Supérieur Pédagogique Mbandaka, DRC, Space Intelligence, UK, Université de Kisangani, DRC, Université Marien Ngouabi, Congo, Université Pédagogique Nationale, DRC, University College London, UK, University of Bremen, Germany, University of Glasgow, UK, Â鶹ÊÓƵ, UK, University of Nottingham, UK, University of South Florida, USA, University of St Andrews, UK.