Abstract ID: 269

Net carbon uptake in undisturbed tropical forests unlikely to offset emissions due to land use change

Land-use change in the tropics is responsible for a considerable fraction of anthropogenic carbon emissions to the atmosphere; however, it is uncertain what portion of these releases may be offset by sequestration in undisturbed tropical forests. Recent results from an analysis of vertical [CO2] profiles and transport models suggests the magnitude of the net C flux in the tropics could only be explained by a sink from the extant undisturbed forests. In contrast, results from a joint ocean-atmospheric inversion suggest a net flux from the tropics comparable to the expected emissions that owe to deforestation, implying no significant sink in undisturbed forests. This study contrasts these two possibilities and reports on a novel scaling methodology to estimate the net carbon flux from undisturbed tropical forests using the best currently available information from ecological studies. It was found unlikely that the average net carbon flux from undisturbed tropical forests was either lower than -1.4 Pg C yr-1 or higher than 1.8 Pg C yr-1 during the period 1998-2005. This analysis suggests that the probability of recent forest carbon fluxes being equal to or larger than carbon emissions due to land-use change is below 10%. These results do not support the hypothesis of a significant net carbon sink in undisturbed tropical forests, an assumption currently incorporated into many simulations of future climate change.

Session:  Carbon - Scaling carbon fluxes to the region from measurements in plots, towers, and aircraft.

Presentation Type:  Poster