GLOBALLY, the terrestrial biota acts as a significant carbon sink for atmospheric carbon dioxide (CO2). The most recent estimate from IPCC for the 1990's puts the terrestrial biota at a net sink of 1.4 gigaton of carbon per year (net carbon uptake by the biota minus emissions from land use changes). It is likely that most of this presumed sink takes place in mid-latitude and tropical forests. Carbon cycle studies in the LBA Experiment indicate that the undisturbed forest of Amazonia may be a strong sink of carbon, at rates from 1 to 7 tons per hectare per year, whereas the wetlands may act as a source of carbon into the atmosphere of up to 1.2 ton per hectare per year. Deforestation and biomass burning in Brazilian Amazonia alone account for a net carbon dioxide emission of about 0,2 gigaton of carbon per year. Notwithstanding the still large uncertainties of these estimates, the balance of observational evidence points to the possibility that the tropical forests of South America function as a sink of carbon from the atmosphere.
