sentences:  Although exact quantities are difficult to measure, human activities have caused substantial losses of soil organic carbon.Of the 2,700 Gt of carbon stored in soils worldwide, 1550 GtC is organic and 950 GtC is inorganic carbon, which is approximately three times greater than the current atmospheric carbon and 240 times higher compared with the current annual fossil fuel emission.The balance of soil carbon is held in peat and wetlands (150 GtC), and in plant litter at the soil surface (50 GtC).