The River Releases Ancient Carbon Into the Atmosphere

Globally, rivers are releasing ancient carbon into the atmosphere, revealing surprising insights for scientists and indicating that human impact on natural landscapes may be more severe than previously understood.

It is already established that rivers emit carbon dioxide and methane as part of the carbon cycle, a rapid gas exchange linked to the growth and decay of organisms, estimated to release around 2 Gigatonnes of carbon annually.

Researchers, including Josh Dean from the University of Bristol, explored the age of this carbon.

The team utilized radiocarbon dating to analyze carbon and methane released from over 700 river segments across 26 countries.

“When we compiled the available data, what we found was surprisingly significant. [Regarding the carbon released], these ancient stores may originate from much older reserves,” Dean states.

Ancient carbon is sequestered in geological formations such as rocks, peat bogs, and wetlands. The findings reveal that around one Gigatonne of this carbon is released annually via rivers, leading to the conclusion that ecosystems are currently removing one Gigatonne less carbon from the atmospheric balance than previously believed.

“This represents the first comprehensive assessment of river emissions on a global scale, which is quite remarkable,” remarks Taylor Maavara from the Cary Ecosystem Studies Institute in Millbrook, New York.

The pressing concern now is understanding the reasons behind the release of such ancient carbon. Factors might include climate change and human activities that alter natural landscapes. Dean observes that the carbon from rivers has appeared “aged” since the 1990s.

“Human activity may be accessing these long-term carbon reservoirs, which can lead to older carbon being released through these channels,” he explains.

For instance, rising temperatures due to climate change can result in carbon being released from thawing permafrost and increase the weathering rates of rocks. Additional factors such as peatland drainage and wetland desiccation could also play a role. Dean emphasizes the necessity for further research to ascertain the degree to which human activities contribute to this phenomenon and how carbon release varies over time.

“This is a critical area of research,” he asserts. “If we believe we are storing old carbon within these reservoirs, we’re mistaken; this understanding is crucial.” These insights carry significant implications for national climate strategies, particularly concerning reliance on natural ecosystems to mitigate ongoing emissions.

“This research raises intriguing questions about how and to what extent we can manage ancient carbon,” says Scott Teig from Oakland University in Rochester Hills, Michigan. He adds that tackling climate change is likely vital to prevent the release of CO2 and methane from these ancient reserves.