A new estimate of changing carbon storage on land since the last glacial maximum, based on global land ecosystem reconstruction

Abstract

A review of global land vegetation 18,000, 8000, and 5000 14 C years B.P. allowed map reconstructions of past ecosystem distribution. By collecting soil and vegetation carbon storage data from the ecological literature, the map reconstructions were then used to estimate the total organic carbon storage on land at each of these time slices. Our best estimate suggests that there was an extremely large increase in land organic carbon storage, of around 1500 Gt (with extreme outer error limits for the increase placed at around 900 and 1900 Gt, respectively) between the Last Glacial Maximum (LGM) and the early-to-mid Holocene. It seems that the world's terrestrial carbon reservoirs more than doubled in size between full-glacial and full-interglacial conditions, due to a great increase in the areas of forest and other carbon-rich ecosystems. Although there are many uncertainties in such calculations, comparing them to methods used in other published estimates, we suggest that the present estimate may represent an overall improvement in accuracy. Apparent problems in previous studies include the use of relatively few data points and a limited range of types of palaeoenvironmental evidence, the unselective use of carbon storage data from anthropogenically modified ecosystems, and the assignment of an anomalously high carbon storage to the LGM `steppe–tundra' ecosystem.