Global warming is a serious problem requiring immediate countermeasures. Large-scale afforestation in and areas for the aim of absorbing CO2 is considered to be one of these measures and the research activities for it have been carried out in Leonora, Western Australia. In this study, the relationship between the biomass distribution and topographic features was examined in order to collect basic information for the selection of suitable afforestation regions in the research area using a biomass distribution map and some topographic elements. The results were as follows. (1) Plant growth is related to the movement of and the volume of runoff water derived from inequality of the ground, which leads to a biased distribution of nutrient accumulation and of surface soil thickness. (2) The total potential biomass estimated from the present topography is greater than the present biomass in the 30 km x 50 km research area. A mass of 319 kt-C could be absorbed in the research area without any improvements in the landform. (3) A substantial improvement on the environment utilizing vast and areas by afforestation is necessary to fix enough carbon deterring global warming.