Mountains cover 25 per cent of the Earth’s surface, and the streams draining these mountains account for more than a third of the global runoff. What had not yet been evaluated, however, was the role mountain streams play in global carbon fluxes (the carbon exchanged between various carbon pools on Earth). So far, scientists had focused mainly on streams and rivers in low-altitude tropical and boreal regions.
Now, scientists have reported the findings of the first large-scale study of the carbon dioxide emissions of mountain streams, and their role in global carbon fluxes. They described their finding as unexpected — mountain streams have a higher average carbon dioxide emission rate per square metre than streams at lower altitudes, due in part to the additional turbulence caused as water flows down slopes.
5% — The proportion that mountain streams account for in the global surface area of fluvial networks.
10%-30% — The likely share of mountain streams in carbon dioxide emissions from all fluvial networks.
The findings appear to indicate that the carbon dioxide comes from geological sources, said the Switzerland-based research institute École polytechnique fédérale de Lausanne (EPFL), whose PhD student Åsa Horgby led the international study, which has been published in the journal Nature Communications.
In a statement on the research, EPFL said the result shows how important it is to include mountain streams in assessments of the global carbon cycle.
The scientists collected big environmental data from the streams draining the world’s main mountain ranges. Then they used these big data to develop a model to estimate the natural carbon dioxide emissions from more than 1.8 million mountain streams worldwide, the EPL statement said.
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