Abstract:Based on emergy synthesis, the cropping system of Weigan River Basin in Xinjiang is chosen as the research object for the exploration of its sustainability and sensitivity from 2000 to 2006. The cropland in Weigan River Basin, a typical mountain\|oasis\|desert system in arid regions, increased rapidly in recent decades and has covered more than 50% of the oases presently. This expansion led to some ecological and environmental problems, which were revealed by the emergy indicators in this research. The results indicate that (1) the total emergy input in the whole basin increased gradually during the concerned period with non\|renewable fuels and renewable environmental resources as the major input into the cropping system, and the emergy input per unit area of cropland increased from the upper to lower reaches; (2) the emergy yield of the cropland increased each year and the emergy yield per unit area increased from the upper to lower reaches, with cotton as the major crop yielding emergy in middle and lower reaches, and maize and wheat for the upper reaches; (3) the Emergy Sustainability Index (ESI), which measures the incremental emergy yield compared to the environmental load, was the highest and relatively stable in the middle reaches due to abundant water resource, high vegetation cover and appropriate non\|renewable fuels input. Comparatively, the ESI in the upper and lower reaches were lower, of which the intrinsic drivers were totally different; (4)As to the sensitivity analysis, the cropping system responds more to the change of non\|renewable fuels than that of renewable environmental resources. Also, it is more sensitive in the lower reaches than in the middle and upper reaches.