Mountain streams cough up surprising levels of carbon

Not enough is understood about the role of alpine streams in the carbon cycle. Keystone / Alessandro Della Bella

Swiss researchers have shown that mountain streams emit far greater levels of CO₂ than previously thought. The finding suggests that the impact of alpine waterways on the environment may have been previously underestimated.  

Despite making up just 5% of the surface area of all rivers around the world, mountain streams are now estimated to account for 10% to 30% of CO₂ emissions from fluvial networks.

These are the findings of researchersExternal link at Lausanne’s Federal Institute of Technology (EPFL), recently published in the journal Nature CommunicationsExternal link.

The team from EPFL’s Stream Biofilm and Ecosystem Research Laboratory (SBERExternal link) measured gas exchanges in Swiss mountain streams. Using this data, they developed a model to estimate the natural CO₂ emissions from more than 1.8 million mountain streams worldwide.

It is thought that mountain streams emit so much CO₂ because they largely run over carbonate rock formed by the skeletons of marine microorganisms that lived millions of years ago when Earth was largely covered by oceans. 

EPFL wants to follow up its initial research by pinpointing more accurately the source of CO₂ escaping from mountain streams and finding out exactly how alpine waterways fit into the global carbon cycle.

“We have known for a number of years that freshwater ecosystems emit roughly the same amount of CO₂ that oceans absorb,” stated Tom Battin, who heads SBER. “We are just starting to discover the role of mountain streams for the global carbon cycle.”