Transport of organic carbon in the world’s rivers

Total transport of organic carbon to the world’s oceans in dissolved and particulate form in rivers is estimated as 0.37 × 10¹⁵ gC yr^-1 by an inventory and extrapolation of data on loss of carbon per unit volume of river discharge from twelve intermediate and large rivers. An alternative estimate of 0.41 × 10¹⁵ gC yr^-1 is derived from measurements of the fluvial loss of organic carbon per unit area of land in various ecosystem types. Rates of loss range from 1 gC m^-2 yr^-1 in grassland systems to 10 gC m^-2 yr^-1 in some forests. Organic carbon transport in rivers is a small flux in the global carbon cycle, but our present understanding is limited by inadequate sampling and few data from major world rivers.