Interaction Between Rural-urban Land Conversion And Its Spatial Scale Effect

As the expense loss caused by the need of the economic growth, rural-urban land conversion is inevitable in the process of economic development. It is also widely recognized that rural-urban land conversion and economic development are closely related. On the one hand, the input of urban construction land is necessary for economic growth, and the only way to increase it is rural-urban land conversion. Since China’s economic growth in recent years relies heavily on factor inputs, rural-urban land conversion is strongly required. On the one hand, agricultural land, especially the arable land, will shrink in the process of rural-urban land conversion, which is a threat to food security, ecological environment preservation and social stability. Consequently, it will become the bottleneck of economic development. Thus, coordinating the relationship between economic growth and rural-urban land conversion is a key issue to sustainable development.In addition, there are obvious scale effects between economic growth and rural-urban land conversion. For one thing, although economic growth of each city and county is related to the conversion of land from rural to urban, the degrees of the correlation are dissimilar. For another, when examining the correlation using different size scales, there are big gaps between conclusions. Conclusions get from study in a certain scale cannot be applied in a larger or smaller scale.Based on economic growth theory and production factor theory, this research selects Wuhan Metropolitan Area as study area. Impulse response analysis, multi-level modeling, and Cobb-Douglas production function are employed to reveal the mechanism of interaction between economic growth and rural-urban land conversion as well as to analyze their scale effect. The conclusions can be taken to provide suggestions for public policies. The research focuses on three aspects:The first one is about the correlation between economic growth and rural-urban land conversion. This research conducts a theoretical analysis of the interaction between economic growth and rural-urban land conversion. It is reported that economic growth depends on the increasing input and utilization of factors of production. Since land is one of the important factors, the growing economy will inevitably lead to high demand for land. The demand mainly concentrates on non-agricultural land, which causes land conversion from rural to urban. Rural-urban land conversion also has an effect on economic growth by stimulating the capital inputs. Therefore, the contribution of rural-urban land conversion to economic growth depends on the quantity and quality of capital inputs stimulated by it. Then, the research performs unit root test, co-integration regression, and impulse response analysis to examine the long-term equilibrium and short-term fluctuations of the interaction between economic growth and rural-urban land conversion in Wuhan Metropolitan Area. The results show that both long-term equilibrium and short-term fluctuations exist in study area, and short-term fluctuations do not have a great effect on the long-term equilibrium. Besides, the response of land conversion to the fluctuation of economic growth is stronger than that of economic growth to the fluctuation of land conversion. It means the contribution of land conversion to economic growth is limited, and the metropolitan area is facing the risk of excessive land conversion.The second one is about the driving effect of economic growth on rural-urban land conversion and its scale effects. At first, social and economic factors affecting rural-urban land conversion are discussed and the framework of the economic driving forces of land conversion is built. Then, the spatial scale effects of all social and economic factors are analyzed. Based on the analysis, the linear hierarchical model of economic mechanism of land conversion is created. Finally, the model is applied at city and county level to measure the effect of economic growth on county land conversion. The results show that①60.53%of differences in land conversion in counties was attributed to the differences at the county level, the other39.47%dues to the differences at the city leve;②GDP growth at both county and municipal level have an positive effect on rural-urban land conversion at the county level;③Municipal GDP not only promotes the rural-urban land conversion at the county level in a direct way, but also has an indirect effect by enhancing the positive correlation between county GDP and land conversion.The third one is about the contribution of rural-urban land conversion to economic growth and its scale effects. A theoretical analysis of land allocation between rural and urban and its efficiency is conducted. Then, regional spatial efficiency equilibrium conditions of rural-urban land allocation are proposed, which is the marginal revenue of rural land is equal to the marginal revenue of urban land in anywhere within the region. The next step is to employ GINI coefficient and Thayer index decomposition method to preliminarily estimate the spatial variations of the contributions of land conversion to economic growth. Finally, two methods, the hierarchical linear modeling and Cobb-Douglas production function, are combined to build a production function model that includes factors at multiple spatial scales. The model is used to analyze the contributions of rural-urban land conversion at the county level to economic growth as well as the influence of factors at the municipal level on land conversion at the county level. The results show thatヾifferences in counties’contribute of farmland conversion to economic growth mainly lie in county level, which means the distribution of farmland conversion need to be mainly relocated at county level with the purpose of improving the spatial allocation efficiency of farmland conversion in the metropolitan area. In addition, differences in counties’ contribute of farmland conversion to economic growth at municipal level is increasing, which means the risk of unreasonable distribution of farmland conversion at municipal level may increase.②63.20%of differences in counties’ economic growth is attributed to the differences at county level and the rest dues to the differences at the municipal level.③the average contribute of non-agricultural land to economic growth is-1.36%,which indicates that large amount of non-agricultural land are wasted and the risk of over-development existed.④the contribution of farmland conversion to economic growth in counties located in municipals with a higher GDP per capita is more than those in counties located in municipals with a relative lower GDP per capita, while the contribution in counties located in municipals with a larger population or a higher urbanization level is less than those in counties located in municipals with a relative smaller population or a lower urbanization level.