Multi-regional Agricultural Sector Computable General Equilibrium Model Construction And Algorithm Optimization

China is an agricultural country with a large population base and inadequate potential cultivated land resources, with the trend of population growth and land resources decrease, also with an increasing tense situation of per capita food and feed grains requirement. In recent years in the context of rapid urbanization, economic growth, population increase and the challenges of ecological environment security in China, how to coordinate the conflicts between cultivated land protection and rapid industrialization, how to deal with the contradiction between cultivated land and urban land expansion, between cultivated land and ecological land, how to maintain a balance between cultivated land supply and per capita food demand are the urgent issues that policymakers and researchers intensively focus on. In order to solve these problems, the key questions are how to use the existing cultivated land and improve land productivity in addition to control population increase and reasonable and scientific land use planning. To achieve these goals, this article intends to carry out the following aspects:Based on the multiple sources datasets of remote sensing images, meteorological data, geographical information and field survey data etc., we estimate cultivated land productivity in China over the next 20 years with the Estimation System for Agricultural Productivity (ESAP) model. At the same time, we introduced two parameters (the agricultural inputs and management level) into the AEZ model which can represent the regional social and economic development. Then we can simulate the impact of regional social and economic condition on the cultivated land productivity. This improvement increase the scalability of ESAP system, which makes ESAP system has more advantages at update data and parameters replacement. Based on the above improvements, we used the ESAP system to estimates the cultivated land productivity and its change tendency at China’s provinces in 2000-2010. Simulated the future climate change using the meteorological data under the mode of Hadley Center’s HADCM3, we simulated the future cultivated land productivity in 2010 and 2020. Preliminary results show that in 2000 and 2010, land productivity in China will show an increasing trend and has a trend of decrease from southwest to northwest step by step. In 2010-2020, land productivity will show a different range of variation, with a growth rate of 10.7% by 2020 compared with 2000 in general, although decreasing trend happened in part of China.In the regional scale, based on the input and output table in 2007 of the whole country and China’s provinces, set the agricultural sector subdivided into 22 departments and build a multiple regional input-output table. According to the demand of data structure of TERM, through the process of calculating the regional trade matrix and adjusting the balance of data structure, get a database of China’s regional TERM in 2007, and provide data support for the regional agricultural policy analysis based on the general Equilibrium Model. On the basis of the framework of general equilibrium model, build a multiple regional Agricultural Sector Equilibrium Model (ASEM), which mainly considering the change of agricultural products in the entire macroeconomic system. Based upon the cultivated land productivity in the year of 2007, assuming the cultivated land area of China’s provinces remain the same, converting the cultivated land productivity change into cultivated land area change in the period of 2010 to 2020, then the change percentages are taken to the ASEM model as the external shock and simulated the impact of cultivated land productivity in China’s provinces on the whole macroeconomic system and main crop yield. Preliminary results show that there has a direct or indirect impact of the whole macroeconomic system especially for the agricultural departments. With the land productivity increase, the crop yield also increase, in the provinces which the cultivated land productivity decrease, the price of agricultural products will increase, but the change trend is not obvious.The change of the regional cultivated land productivity for the whole macro economy system, especially the agricultural departments have a direct or indirect impact. Land productivity increase the crop yield will also rise, the provinces and cities of cultivated land productivity decline the provinces and cities of the agricultural prices will have to increase, but the change trend is not obvious.The paper has realized the breakthrough on the aspects of database building, model building and algorithm optimization. First, finishing a set of database including surface climate characteristics, land element data and input and output data in which the agricultural sector subdivided into 22 departments. Second, according to the ESAP model, dynamically evaluate the change trend of cultivated land under the potential climate change scenarios in China’s province. Third, based on the variation characteristics of cultivated land productivity, build an Agricultural Sector Equilibrium Model (ASEM) to reveal the influence rules of cultivated land change on future regional food security, and provide valuable reference for the China’s grain production decision making.