Rivers are leaking ancient carbon back into the atmosphere

Carbon stored in landscapes for thousands of years is leaching back into the atmosphere via rivers, and human activity may be to blame

By Madeleine Cuff

4 June 2025

Rivers such as the Chuya in Russia can be a source of carbon dioxide and methane

Parilov/Shutterstock

Rivers around the world are leaking ancient carbon back into the atmosphere. The finding has taken scientists by surprise and suggests human activities are damaging the natural landscape far more than first thought.

Researchers already knew rivers released carbon dioxide and methane as part of the global carbon cycle – the short-term movement of gases that happens as living things grow and decompose. They are thought to emit around 2 gigatonnes of this carbon each year.

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But when Josh Dean at the University of Bristol, UK, and his colleagues set out to determine how old this carbon really is, they found that around 60 per cent of global river emissions are from thousands-of-years-old stores.

The team used radiocarbon dating to assess the age of carbon and methane released from more than 700 river segments across 26 countries.

“What really surprised us, when we compiled all the data that we could get, was that [more than half of the carbon being released] could be coming from these much, much older carbon stores,” says Dean. “There’s a sort of continuous leak, or sideways flow, of these older carbon stores.”