Estimates of the storage and flux of shelf carbon in vegetation, soils, carbonates, and organic matter during the period of the marine transgression since the Last Glacial Maximum (LGM) 18 ka are presented. Whereas at present each square metre of land on the planet carries about 10.65 kg of carbon in vegetation and soils, during the LGM most areas of exposed continental shelf carried relatively little carbon, probably about 5.86 kg C m−2, but this increased to a maximum density of 15.49 kg C m−2 after 10 ka when conditions generally favoured peat deposition and forest development. In the ensuing sea level rise up until mid-Holocene time this large store of carbon was displaced. Assuming an average value of 10.65 kg m−2 carbon (combining the land lost to sea-level rise before and after 13 ka), a transgression covering 15–23×1012 m2 would mean that 160 to 245 Gigatons of Carbon (1 Gt=1012 kg) were lost from the terrestrial system at the same time that the remainder of the terrestrial biosphere was still taking up organic carbon. This additional and opposite flux from the land system must be taken into account when considering changes in the global carbon cycle and CO2 fluxes. Moreover, it complicates the interpretation of the ocean carbon isotope record. Peer reviewed