Annual emissions of CO(2), CH(4), CO, N(2)O, and NO(x) from biomass burning in shifting cultivation systems in tropical Asia, Africa, and America were estimated at national and continental levels as the product of area burned, aboveground biomass, combustion completeness, and emission factor. The total area of shifting cultivation in each country was derived from the Global Land Cover 2000 map, while the area cleared and burned annually was obtained by multiplying the total area by the rotation cycle of shifting cultivation, calculated using cropping and fallow lengths reported in the literature. Aboveground biomass accumulation was estimated as a function of the duration and mean temperature of the growing season, soil texture type, and length of the fallow period. The uncertainty associated with each model variable was estimated, and an uncertainty and sensitivity analysis of greenhouse gas estimates was performed with Monte Carlo and variance decomposition techniques. Our results reveal large uncertainty in emission estimates for all five gases. In the case of CO(2), mean (standard deviation) emissions from shifting cultivation in Asia, Africa, and America were estimated at 241 (132), 205 (139), and 295 (197) Tg yr(-1), respectively. Combustion completeness and emission factors were the model inputs that contributed the most to the uncertainty of estimates. Our mean estimates are lower than the literature values for atmospheric emission from biomass burning in shifting cultivation systems. Only mean values could be compared since other studies do not provide any measure of uncertainty.
