Tuesday, July 29, 2025

World’s largest tropical peatlands revealed to be more than 40,000 years old

University of Leeds

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.

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.

Dr Greta Dargie 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”.

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, the work of Dr Dargie and others 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.

The new study, published today in the scientific journal Environmental Research Letters, began with teams of scientists trekking through remote and inaccessible peat swamps in both the Congo and 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.

It is not just the great age of the peatlands which came as a surprise to the scientists. Prof. 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.

“The great age of the peatlands drives home how valuable they are,” said Dr Pauline Gulliver of the University of Glasgow, a co-author of the study.

“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.”

Ends

Photos available here

Photo credits

P2310474: swamp forest, DRC. Credit: Greta Dargie

P1030272: palm swamp forest, Congo. Credit: Ian Lawson

P2310868: peat core, Congo. Credit: Greta Dargie

20190727_111213: The field team moving camp to a new field site by boat, DRC. Credit: Greta Dargie

Further information

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, University of Leicester, UK, University of Nottingham, UK, University of South Florida, USA, University of St Andrews, UK.

For media enquiries, please contact Kersti Mitchell via k.mitchell@leeds.ac.uk

University of Leeds

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Journal

Environmental Research Letters

DOI

10.1088/1748-9326/ade905

Method of Research

Survey

Subject of Research

Not applicable

Article Title

Timing of peat initiation across the central Congo Basin.

Article Publication Date

29-Jul-2025

Researchers reveal role of wetlands in terrestrial carbon sink change

Chinese Academy of Sciences Headquarters

image:
Spatial pattern of global wetland carbon sequestration
view more
Credit: LI Junjie

Wetlands are among the most efficient ecosystems for carbon (C) sequestration, storing more than 30% of global soil C in only 3–13% of Earth's land surface. However, the spatiotemporal patterns of wetland C uptake and their role in regulating global land C sink dynamics have been poorly quantified. As a result, wetlands have not been explicitly incorporated into the models used to constrain the global C budget, making it difficult to accurately estimate land carbon sink and formulate evidence-based wetland management policy.

To address this problem, a research group led by Prof. DING Weixin from the Institute of Soil Science of the Chinese Academy of Sciences has utilized a newly developed dynamic global wetland water level (WL) dataset to assess the spatiotemporal dynamics of wetland carbon sequestration from 2000 to 2020.

Their findings were published in Nature Ecology & Evolution.

The researchers compiled 934 in situ observations from 258 peer-reviewed publications and the FLUXNET database to estimate a global mean wetland net ecosystem production (NEP) of 56.4 g C m‒2 year‒1. By integrating the NEP dataset with environmental datasets and machine-learning models, they estimated a mean annual global wetland C sequestration of 1,004 Tg C for the period 2000–2020, with 70% contributed by tropical wetlands.

They discovered that South America, Asia and Africa were the top three continents for wetland C sequestration, collectively accounting for 79% of the global total.

The study further revealed that global wetland C sinks declined through 2005, followed by a subsequent recovery. Overall, global wetland C sequestration was roughly stable over the two-decade period, with gains in northern mid-high latitudes offsetting declines in the tropics and southern mid-high latitudes. At the continental scale, South America's capacity for wetland C sequestration decreased during the study period, completely offsetting collective wetland C sink gains in Africa, North America, Asia, and Europe.

This study highlights hydrological change as a primary driver of increasing regional variability in wetland C sinks. It also notes that intensifying hydrological extremes resulting from climate change may undermine the resilience of wetland C sinks and the ecosystem services they support.

Finally, based on the estimates from Friedlingstein et al. (2022), the researchers found that terrestrial C sink growth rates decreased from 0.075 Pg C yr‒2 (P < 0.05) during the period 1980‒1999 to 0.037 Pg C yr‒2 (P > 0.05) during the period 2000–2020. The temporal trajectory of global wetland C uptake from 2000 to 2020 showed a positive correlation with terrestrial C sinks and can explain 33% of temporal variations in terrestrial C sinks.

These findings provide a crucial new perspective: The leveling off of wetland carbon sequestration has significantly contributed to slowing the increase in global terrestrial carbon sink in recent decades. All in all, this study provides important new data for global C evaluation reports such as those by the Intergovernmental Panel on Climate Change.

Temporal patterns in global and regional wetland carbon sequestration

Wetland carbon sinks versus land carbon sinks across the globe

Credit

LI Junjie