August 29, 2012
The results are based on a new emissions tracking system developed by researchers at Brazil's National Institute for Space Research (INPE) and other institutions. The system uses satellite data and biomass maps to estimate carbon emissions on an annual basis.
According to Nature, the 20 percent difference between the drop in annual forest clearing and emissions can be partly attributed to "a natural lag as carbon stocks slowly decay and make their way into the atmosphere as carbon dioxide." However it reflects that deforestation is increasingly occurring in denser rainforests, which store more carbon than the transition forests in the southern Amazon. Accordingly, the model estimates average biomass of deforested areas at 198 tons of carbon per hectare in 2005 and 218 tons per ha in 2011. The results also suggest that forest regrowth may not be sequestering as much carbon as hoped since secondary forests may be cleared after regrowth.
Nature notes the methodology may not fully account for emissions from degradation resulting from logging. The researchers are working on that issue.
Imazon, a Brazilian NGO, also has a system for tracking carbon emissions from deforestation, which is based on the group's own deforestation monitoring system. Imazon releases monthly updates "committed" emissions from deforestation — emissions that will eventually result from forest clearing after the vegetation decays.
CITATION: Aguiar, A., et al (2012), Modeling the spatial and temporal heterogeneity of deforestation-driven carbon emissions: the INPE-EM framework applied to the Brazilian Amazon. Global Change Biology. doi: 10.1111/j.1365-2486.2012.02782.x