Congo Basin ancient carbon
© Matti Barthel / ETH ZurichBlackwater lakes and rivers in the central Congo Basin are releasing carbon that is up to 3,500 years old.
Blackwater lakes and rivers in the Congo Basin are releasing ancient carbon into the atmosphere, a new study shows. Previously, scientists thought this carbon was safely stored in the surrounding peatlands, but the research reveals that's not the case.

The finding contradicts the long-held assumption that old peat carbon remains trapped underground, suggesting that some tropical peatlands could switch from being carbon sinks to major carbon sources.


Comment: That's assumptions for you! If they'd been reading the Signs, they'd have noticed northern and Arctic peatlands 'catching fire', in winter, and made the connection to carbon/methane outgassing.


"We are now faced with a 30-million-tonne question: we need to determine if this is just a small, natural leakage of ancient carbon, or the onset of broadscale destabilization," study lead author Travis Drake, a carbon biogeochemist at the Swiss Federal Institute of Technology Zurich (ETH Zurich), told Live Science in an email.


Comment: Our informed guess is for the "onset of broadscale destabilization". See also:

Swarm reveals growing weak spot in Earth's magnetic field
Published this month in Physics of the Earth and Planetary Interiors, the latest results from the Swarm mission reveal that while the South Atlantic Anomaly expanded steadily between 2014 and 2025, a region of the Atlantic Ocean southwest of Africa has experienced an even faster weakening of Earth's magnetic field since 2020.

"The South Atlantic Anomaly is not just a single block," says lead author Chris Finlay, Professor of Geomagnetism at the Technical University of Denmark. "It's changing differently towards Africa than it is near South America. There's something special happening in this region that is causing the field to weaken in a more intense way."
This behaviour is linked to strange patterns in the magnetic field at the boundary between Earth's liquid outer core and its rocky mantle, known as reverse flux patches.

Prof. Finlay explains, "Normally we'd expect to see magnetic field lines coming out of the core in the southern hemisphere. But beneath the South Atlantic Anomaly we see unexpected areas where the magnetic field, instead of coming out of the core, goes back into the core. Thanks to the Swarm data we can see one of these areas moving westward over Africa, which contributes to the weakening of the South Atlantic Anomaly in this region."

Drake and his colleagues have conducted three research trips to the Congo Basin over the past four years. Specifically, the team traveled to the Cuvette Centrale, a 56,000-square-mile (145,000 square kilometers) region of forests and swamps in the Democratic Republic of the Congo that holds Earth's largest known tropical peatland complex. Situated in the heart and to the south of the Cuvette Centrale are two large blackwater lakes — Lake Mai Ndombe and Lake Tumba — while a major blackwater river, the Ruki River, flows west-northwest across it to meet the Congo River.

Blackwater lakes and rivers contain high levels of decaying plant debris, or dissolved organic carbon, which gives them their black color. This dissolved organic matter, together with direct inputs of carbon dioxide (CO2) from the surrounding swamps and forests, creates supersaturated concentrations of CO2 in lakes Mai Ndombe and Tumba and in the Ruki River. As a result, these waters emit enormous amounts of CO2 into the atmosphere.

Crucially, however, none of the CO2 was previously thought to originate from the Cuvette Centrale's ancient peat, as these deposits, protected from decomposition by their oxygen-depleted, waterlogged environment, were believed to be highly stable.

But in a paper published Feb. 23 in the journal Nature Geoscience, Drake and his colleagues found otherwise. Their results showed that a significant proportion of the CO2 escaping the Cuvette Centrale's blackwater bodies is from peat carbon that is between 2,170 and 3,500 years old.

"We were very surprised because we fully expected the carbon dioxide to be modern," Drake said.


Comment: Because you believe your AGW assumptions, which are false.


The researchers drew their conclusions from measurements they took at Lake Mai Ndombe in 2022 and 2024, and at Lake Tumba and the Ruki River in 2025. They accessed Lake Mai Ndombe with small boats, which was difficult due to strong winds that almost capsized them, Drake said.

Congo Basin study
© Matti Barthel / ETH ZurichScientist Pengzhi Zhao gets ready for another day of sampling. Most locations are almost impossible to reach by land. Therefore, small dinghy boats were used to access these remote sites in the central Congo Basin.
"The ecosystems remain in relatively pristine condition," he said. "There are some small settlements and villages scattered around Lake Mai Ndombe, but they are far and few between."


Comment: In short, they can't blame humans for this.


The team measured sediments, greenhouse gases, dissolved organic carbon and dissolved inorganic carbon, which includes dissolved CO2, bicarbonate ions (HCO3-) and carbonate ions (CO32-). Later, in the lab, the researchers analyzed their samples with high-precision spectrometry to separate modern carbon from plants and older carbon from soils.

"Because the organic carbon in the lake was modern, we assumed the inorganic carbon would be too, so we initially just analyzed a single sample to confirm," Drake said. But when about 40% of the inorganic carbon in that sample turned out to be millennia old, the team decided to test the remaining samples.

The results were consistent across Lake Mai Ndombe, so the researchers returned to the Cuvette Centrale to sample Lake Tumba and the Ruki River. Both contained high levels of inorganic carbon derived from ancient peat, suggesting that microbes in the region are breaking down peat carbon into CO2 and methane, which then seep into lakes and rivers before wafting into the atmosphere.

congo basin, fimi and kawai
© Matti Barthel / ETH ZurichAt the confluence of the Fimi and Kawai rivers in the Congo Basin, dark water from forest landscapes meets rust-colored water tinted by iron oxides from the savannas.
The Cuvette Centrale is estimated to hold one-third of the carbon stored in tropical peatlands globally, equivalent to about 33 billion tons (30 billion metric tons). It's possible that recent losses of ancient peat carbon are linked to the formation of new peat deposits, in which case the phenomenon might be nature returning to a state of equilibrium, according to the study. But it's also possible that climate change is destabilizing long-buried deposits and that the Congo Basin's peatlands are nearing a tipping point.


Comment: Or more accurately, and literally, Earth Changes: signs of activity in the central heating of Earth's core.


"This pathway highlights a critical vulnerability," Drake said. "If the region experiences future drought, this export mechanism could accelerate, potentially tipping these massive carbon reservoirs from a sink into a major source to the atmosphere."

Next, the researchers will analyze water trapped in the Congo Basin's peat to explore if and how microbes are releasing ancient carbon.

"Ultimately, we aim to confirm whether this process is happening across the entire Cuvette Centrale and quantify oxidation rates to determine if this leakage is a natural baseline or a sign of instability in this large carbon reservoir," Drake said.