Evaluation of agricultural sustainability based on human carrying capacity in drylands--a case study in rural villages in Inner Mongolia, China

In China, desertification, rapid economic growth, and enforcement of a policy of converting cultivated land back into forest and pasture (land conversion policy) have a great impact on rural life and threaten agricultural sustainability, which induces emigration to other places, over-exploitation of resources, or lower quality of life, resulting in the collapse of a village. Among many indicators that have been developed for evaluating agricultural sustainability, we used a method that compares human carrying capacity (HCC) with the actual exploitation level of resources. The purposes of this study were to construct a model for estimating HCC from the viewpoint of supply and demand of resources and to evaluate agricultural sustainability by applying the model to a rural area in Inner Mongolia, China. The model was constructed on the basis of a field-level survey of the study area. Land productivity, land use composition, demand for biomass per capita, and prices of agricultural products, all of which influence HCC, were used as the model's input parameters. Field investigations were conducted to determine the values of these parameters. The ratio of present population density to HCC, called the “rate of population accommodation”, is a useful indicator for evaluating agricultural sustainability. Predicting the rate of population accommodation in 2010 allowed us to draw two conclusions. First, rural life in the study area will be threatened by 2010 if the land conversion policy is continued and crop productivity does not increase. Second, the quality of life in the study area will be maintained in 2010 if an increase in crop productivity makes up for the decrease in economic productivity per unit land caused by the land conversion policy. Therefore, given the policy, it is important to develop more effective production methods for increasing crop productivity.