Abstract ID: 199

Modeling carbon emissions from multiple land use transitions in southern Amazonia

Fires for deforestation and other land cover changes in southern Amazonia are an uncertain but significant source of carbon emissions to the atmosphere. Recent expansion of mechanized cropland in the region has increased the rates, clearing sizes, and combustion completeness of forest and Cerrado conversion compared to previous deforestation for cattle ranching. To more accurately quantify the influence of agricultural intensification on carbon emissions, we developed a high-resolution (250 m) model of DEforestation CArbon Fluxes (DECAF). DECAF estimates variations in forest and Cerrado biomass based on time series of MODIS NDVI and explicitly tracks the duration and combustion completeness of new deforestation as a function of post-clearing vegetation phenology and MODIS-based fire frequency. In our model runs for the Brazilian state of Mato Grosso, we quantified the contribution of fires for deforestation, conversion of pasture and Cerrado to mechanized cropland, and pasture maintenance to total fire emissions under low, middle, and high emissions scenarios. During 2001-2005, carbon losses from all types of deforestation were 48-82 Tg per year (mean = 67 Tg C), representing approximately 74% of annual fire emissions in the study region. Cropland expansion in non-forest areas contributed 19% of estimated fire emissions, while maintenance fires in pasture and Cerrado land cover types averaged 7% of all fire emissions during 2001-2005. In total, DECAF-based emissions for Mato Grosso represent 1/3 of estimated fire emissions for all of southern hemisphere South America during this period. Our results suggest that effective policies to reduce emissions in this region would promote intensification of already-cleared land for cropland conversion and would target large (>25 ha) rather than small clearings.

Session:  Carbon - Effects of land-cover/land-use change in carbon stocks.

Presentation Type:  Oral