The Amazon basin has seen a shift in biomass burning from relatively more forest fires in the early 2000s to a larger proportion of savanna/agricultural fires in the late 2000s. That is according to researchers from Stanford University, US, NASA/GSFC/Laboratory for Atmospheres, US, and the University of São Paulo, Brazil, who used satellite data on land cover, aerosol optical depth, single scattering albedo, and precipitation.
"We attribute this shift in part to enhanced forest law enforcement and lower deforestation rates that reduced forest fires in the latter 2000s," John Ten Hoeve of Stanford University told environmentalresearchweb. "The increase in savanna/agricultural fires in 2007 and 2010 is due in part to drought conditions during these years, but also to increased agricultural and pastoral development on already degraded land rather than newly deforested land, a change which has been shown in other recent studies."
According to Ten Hoeve, thick smoke palls made of tiny aerosol particles cover much of the Amazon region during the biomass burning season. The smoke comes from burning of both forest and savanna/agricultural areas. Recently cut forest is burnt to develop agricultural or pastoral land while fires are lit on existing agricultural or pastoral land to mobilize nutrients, control pests or remove brush and litter.
"Fire ignitions are largely anthropogenic but fire spreading is mainly affected by natural factors such as drought," he explained. "Another implication of this study is if droughts worsen over the Amazon with climate change – two of the worst droughts in the last century occurred in 2005 and 2010 – the increase in forest-fire spreading may offset current and future reductions in anthropogenic fire ignitions."........