[2013] A large flux of CO2 from inland waters to the atmosphere

Carbon dioxide (CO2) transfer from inland waters to the atmosphere, known as CO2 evasion, is a component of the global carbon cycle. Global estimates of CO2 evasion have been hampered, however, by the lack of a framework for estimating the inland water surface area and gas transfer velocity and by the absence of a global CO2 database.

In this new study, the authors have reported regional variations in global inland water surface area, dissolved CO2 and gas transfer velocity. They obtain global CO2 evasion rates of 1.8 petagrams of carbon (Pg C) per year from streams and rivers and 0.32 Pg C per year from lakes and reservoirs.

The resulting global evasion rate of 2.1 PgC yr-2 is higher than previous estimates owing to a larger stream and river evasion rate. This analysis predicts global hotspots in stream and river evasion,with about 70 per cent of the flux occurring over just 20 per cent of the land surface. The source of inland water CO2 is still not known with certainty and new studies are needed to research the mechanisms controlling CO2 evasion globally.

Reference: Raymond, P.A., Hartmann, J., Lauerwald, R., Sobek, S., McDonald, C., Hoover, M., Butman, D., Striegl, R., Mayorga, E., Humborg, C., et al. (2013). Global carbon dioxide emissions from inland waters. Nature 503, 355–359.