Conduits of the carbon cycle

Abstract

Emissions of carbon dioxide from inland waters to the atmosphere are a crucial link in the global carbon cycle. A comprehensive analysis reveals that this connection is much stronger than was previously thought. See Article p.355 There has been a growing recognition in recent decades that inland waters release considerable amounts of CO2 into the atmosphere. Until now it has been difficult to obtain global estimates of how much carbon is transferred in this way. This study combines new data sets with a systematic approach to the problem and estimates the global emission rate at about two petagrams of carbon per year from streams, rivers, lakes and reservoirs, which is higher than previous figures because of the contributions from streams and rivers. This new analysis also identifies global hotspots in stream and river evasion, with about 70% of the CO2 flux occurring over just 20% of the land surface.