Research On Change And Moderation Of Urban Land Development Intensity In The Yangtze River Delta

Land,as a non-renewable and scarce resource,is the base of human survival and development,and the carrier of urban space and function.Land plays an impartment role in attaining the city's sustainable development and city's competitive power.There rarely has any research about land development intensity represented the ratio of construction land to the whole land.The reasonable control of urban land development intensity is not only the key issues of sustainable land use,but also a difficult problem.However,there are individual studies about urban land development intensity,the depth and breadth of the research cannot meet the need of city development.It is necessary to further study on urban land development intensity.The Yangtze River Delta region is one of the most developed economic regions,where the suburb urbanization accelerated the expansion of urban space since late in 1990's.With the land use type transformed greatly and the growth rate of city scale increased,many arable lands,water surface and forest land also changed into construction land,and deterioration tendency of ecological system aggravated obviously.In recent years,the rapid expansions of urban construction land pose a serious threat to the ecological space,which makes the urban ecological environment worse and worse.The urban ecological security is facing a severe test and challenge.Therefore,for the cities located in the Yangtze River Delta,that strict control of urban construction space and the determination of rational construction proportion have certain significance in avoiding the encroachment of construction space to other spaces and influence of urban sustainable development.Through this study,some reference will be given for sustainable utilization of urban land in the Yangtze River Delta region.Through the review of domestic and overseas research,we found that at present the researches are mainly focused on driving forces,ecological effects,and control of moderate scale for urban land use.In the studies on urban land development intensity,most studies focused on land development intensity represented by plot ratio,building density and building height.There rarely has any research about land development intensity represented the ratio of construction land to the whole land.The reasonable control of urban land development intensity is not only the key issues of sustainable land use,but also a difficult problem.However,there are individual studies about urban land development intensity,the depth and breadth of the research can not meet the need of city development.It is necessary to further study from the variation characteristics,the driving force,eco-environmental effects,and moderate range.In the urban land scale theory,the harmonization theory of urban land use,resource environmental bearing-capacity theory and moderation theory,there is a deep exposition about harmony among urban land development intensity,economy and environment.It also will lay a foundation for further studying of urban land development intensity.In the process of probing law,through the analysis about urban land development intensity in the last ten years,we find that there are obvious spatial and temporal characteristics in the Yangtze River Delta region.On the whole,the urban land development intensity has a tendency to increase during 2002-2012,and formed a series of high intensity areas centered on "Nanjing-zhenjiang-wuxi-suzhou-shanghai" and"Hangzhou-shaoxing".The change range of land development intensity has significant characteristics of spatial differentiation,and it is higher in north and east coast of Jiangsu and south of Zhejiang.With the rapid development of regional integration of the Yangtze River Delta region,the urban land development intensity has tending to balance because of the senility of regional environment.The comparation result between every city and the whole region shows that the urban land development intensity of most cities is higher than average level of Yangtze River Delta region.The comparation result between the Yangtze River Delta region and the whole nation shows that,the urban land development intensity is relatively high in cities of the Yangtze River Delta,and the urban land development intensity in most cities is higher than the national average level.The comparation result of different provinces of the Yangtze River Delta region shows that,provincial difference is much larger than provincial internal difference of urban land development intensity.The comparation result of different cities shows that the average annual change rate of urban land development intensity is greatly different;it is bigger in the smaller cities than bigger cities.In the process of revealing mechanism,the paper deeply analyzes the formation mechanism of change characteristics and eco-environment effects by using econometric model,from two aspects of driving force and ecological effects of urban land development intensity change,and expounded variation overly and systematically the causes and results of urban land development intensity change.In the analysis of formation mechanism of change characteristics,we attempt to analyze based on driving force in the paper,and select some driving factors and create driving model.The results show that there are close relation during urban land development intensity and economic total,investment level,industrial structure in the Yangtze River Delta.There is a positive correlation between the factors and urban land development intensity.It means that the urban land development intensity is the result from above all factors driving.There is also obvious spatial differentiation about driving factors,which is the important formation reason of change characteristics of urban land development intensity.Meanwhile,the change of urban land development intensity leads to resource problem,environmental problem,and ecological problem directly or indirectly.Combined with the ecological environment status of the Yangtze River Delta,ecological effects of urban land development intensity is analyzed by using qualitative and quantitative methods from three aspects of resource consumption effect,pollution emission effect and ecological service effect.The results show that eco-environmental effects of urban land development intensity are obvious from the whole region of the Yangtze River Delta.But in the different classifications which according to city size,different province and intensity level,there are great differences about eco-environment effect of urban land development intensity.As the carrier of urban development,urban land development intensity is driven by a variety of factors,such as economic,social,and demographic,and it showed consistent upward trend.Meanwhile,resource and environmental effects aroused also changed with the increasing of urban land development intensity.The more obvious is that the resource consumption and pollutant emissions increase,and the effects of ecosystem services reduce.The resource environmental bearing-capacity is limited for all cities,in the case of land development intensity increasing constantly,the eco-environmental effects beyond the scope of city resource environmental bearing-capacity finally,and makes the urban ecological environment bearing enormous pressure.It may have effect on people's living standards and hinder the sustainable development of urban economy.Therefore,the urban land development intensity must be within the range of resource environmental bearing-capacity,and the development intensity level also must be constrained by resources and environment carrying capacity.However,the city's construction and development must guarantee by a certain amount of land.The lack of land will restrict the amount of urban economic development,and affect the normal functioning of urban functions directly.In summary,under the "demand-driven" and "environmental constraints",urban land development intensity levels need to seek a balance between the two.In this study,a more systematic theoretical discussion is made about moderation of urban land development intensity.Content,mechanisms and criteria of moderation are explicated.And based on the harmonization theory,models are built which are about a moderate range determined of urban land development intensity.At last,moderate range is determined for 25 cities in the Yangtze River Delta and moderate status are judged.The results show that,there is big difference in the range of urban land development intensity.And the state of cluster is formed in spatial distribution.According to the analysis of moderation,the cities could be divided into four types:serious over,common over,common moderation,well moderation.Based on the moderate state analysis,approaches should be taken.But these approaches must be related to local conditions,and must be taken into account the major difference about urban land development intensity and moderate status,and urban land development intensity,resources and environment and social development among cities of the Yangtze River Delta.We should set down differentiated goal and effective management policy,by comprehensive use of administrative means,economic means,technical means,with some policy instruments such as land-use planning,land supply plan,land prices and land taxes.This will not only provide new ideas for improving urban land use and land management in the Yangtze River Delta region,but also has important theoretical and practical significance to promote urban sustainable development in the region.