An accurate estimation of the biomass density in forests is a necessary step in understanding the global carbon cycle and production of other atmospheric trace gases from biomass burning. In this paper the authors summarize the various approaches that have developed for estimating above ground biomass density of tropical forests relying for the most part on forest inventory data and modeling in a geographic information system (GIS). To capture the spatial distribution of biomass density, we have developed a GIS model of the biophysical parameters that influence the distribution of biomass density. This model was combined with forest inventory and human population density data to produce a spatially explict estimation of biomass density both under natural conditions and with the influence of human activity.