Rivers leaking ancient carbon back into the atmosphere

Why in News

According to a research conducted by scientists at the University of Bristol, ancient carbon stored in the earth's crust for thousands of years is leaking into the atmosphere as carbon dioxide (CO₂) and the source of this CO₂ is the world's rivers.

About the research

• For this research, published in the journal Nature, the international research team studied more than 700 rivers in 26 different countries around the world.
• To date the river carbon, detailed radiocarbon measurements of CO₂ and methane were taken from rivers and the levels of carbon-14 in the river samples were compared to the standard reference of modern atmospheric CO₂.

Research results

• Ancient carbon stores are leaking into the atmosphere at a much higher rate than previous estimates.
• This research challenges previous assumptions about the global carbon cycle, which thought most river emissions came from plants (fresh carbon reserves) that have moved into the river system in the last 70 years.
• The new study suggests the opposite, with more than half of the emissions coming from long-lived carbon reserves deposited thousands of years ago or even earlier.
• According to the research, plants and shallow soil layers are removing about one gigaton more CO₂ from the atmosphere each year than is being offset by the leakage of ancient carbon.

Significance

• Carbon emissions from rivers are globally significant, and more than half of these emissions are coming from carbon reserves that we think of as relatively stable.
• This means we need to re-evaluate these important parts of the global carbon cycle.