27 Estimation of Optimum Population Scale Based on Arable Land and Terrain Constraints in the Mountains Region of Southern Gansu Province in China

Based on two indexes of per capita grain and economic level, this paper estimates local human carrying capacity for the subsistence life, the relative ample life and the well-off life and also the relationship between population and agricultural resources in 10 county-level districts in the mountainous region of southern Gansu, China that suffered serious destruction from 5.12 scale earthquake on May 12, 2008. The results show that total population scale is overloaded even at the subsistence level in this region. This population scale is larger than ones of the subsistence level and smaller than ones of the relative ample life, and it is difficult to achieve the target of well-off life.