Congo alarm: Earth’s ancient carbon reservoirs are leaking into the atmosphere

ZURICH — Scientists have discovered that blackwater lakes in the Congo Basin are releasing massive amounts of carbon dioxide, with a significant portion of the gas originating from ancient carbon stored for thousands of years in peatlands.

The findings, published in the journal Nature Geoscience, resulted from a study led by researchers at ETH Zurich in Switzerland.

The research focused on two major bodies of water, Lac Mai Ndombe and Lac Tumba. Using radiocarbon dating, the team determined that up to 40% of the escaping CO2 comes from ancient peat deposits.

Scientists described the phenomenon as a "leak" in one of the world's most critical carbon sinks. The Congo Basin holds approximately one-third of the planet’s total tropical peatland carbon.

While experts previously believed these carbon stores were stable, the study warns that deforestation and droughts caused by climate change could worsen the situation.

The research also found that low water levels during the dry season lead to increased emissions of methane, another potent greenhouse gas.

Recent findings in the Congo Basin represent more than a localized environmental study; they challenge a foundational axiom of climate science regarding the stability of tropical peatlands. Long categorized by the scientific community as secure "carbon sinks"—geological vaults that sequester rather than emit—these ecosystems are now showing signs of systemic leakage. Most alarmingly, the discharge includes "ancient carbon" that has been sequestered for millennia.

The distinction between the release of ancient and contemporary carbon is a critical inflection point for climate policy. While the decomposition of recent organic matter is a standard component of the biogenic cycle, the venting of ancient carbon reserves suggests a breakdown of a once-balanced system. This creates a high risk of a "positive feedback loop": as climate change desiccates peatlands, the drying soil releases legacy carbon, which in turn accelerates global warming, further intensifying the drying process.

These results also expose a significant blind spot in current global climate modeling. The failure to fully integrate the role of tropical wetlands and lake systems suggests that existing projections for the pace of global warming may be fundamentally understated and require urgent recalibration.

While the primary research centers on Africa, the findings serve as a severe warning for other critical carbon frontiers, most notably Southeast Asia. The vast peatlands of Indonesia, Malaysia, and the Mekong Basin are already under intense pressure from deforestation and shifting precipitation patterns. The likelihood that these regions are also silently hemorrhaging ancient carbon underscores the urgent necessity of prioritizing peatland preservation within global climate stability frameworks.