An Exploration Of The Relationship Between Urban Land Expansion And Population Growth Of Prefecture-level Cities In China

China is in the period of rapid urbanization development.The inconsistency between land urbanization and population urbanization have led to urban land inefficient sprawl and low-efficiency land use,which poses a threat to the healthy development of cities.Population density is a direct reflection of the relationship between population and land.The rate of land expansion is faster than that of population growth,the overall population density would decrease in urban built-up areas and increase in per capita construction land.Therefore,revealing the relationship between urban land expansion and population growth in China is of great significance to promote coordinated development of human and land and healthy development of cities.Based on the urban resident population and built-up areas in 285 cities in China during 2006-2016,this paper analyzes the spatial and temporal evolution characteristics of urban land expansion and population growth in China,and reveals the changes and characteristics of population density during urban development in China.On this basis,this paper explores the influencing factors of population density change.The results show that:(1)The rate of urban expansion is generally faster than the rate of population growth.At the national level,the average annual growth rate of urban population and built-up area is 2.75% and 5.26% during 2006-2016,respectively.and the growth rate of built-up areas is close to twice the rate of population growth.The rate of the built-up area growth is close to twice the rate of population growth.The law of urban land expansion faster than population growth shows that in different scales,different regions and different urban agglomerations,while the difference is significant.Among cities of different scales,the population growth of mega-cities is the fastest and the expansion of built-up areas is the slowest,while the expansion of built-up areas of big-cities is the fastest and the population growth rate is less than that of mega-cities.Among different regions,the population and built-up areas growth are the fastest in eastern,while the built-up areas and population growth are the slowest.Among the different urban agglomerations,the population and built-up areas of Chengdu-Chongqing urban agglomerations grow fastest,the population growth of the Pearl River Delta is the slowest,and the growth of the Beijing-Tianjin-Hebei built-up area is the slowest.In terms of spatial distribution,the spatial distribution pattern of urban land expansion and population growth is generally similar in China.(2)The average population density of Chinese cities on multiple scales is decreasing with time,and the difference is significant.Overall,the average urban population density in China is decreasing at an average annual rate of 2.39% during 2006-2016.Among cities of different scales,the population density of large cities has the largest decline,and the population density of megacities has the smallest decline.Among the different regions,the population density in the east decreases the most,and the population density in the central region decreases the least.Among the different urban agglomerations,the population density decreases from large to small,followed by Chengdu,the Pearl River Delta,the Yangtze River Delta,the middle reaches of the Yangtze River,and Beijing-Tianjin-Hebei.(3)The population density of 85.3% cities in the whole country declines,while there is a significant difference of the changing rate of population density among cities.Cities with rapidly decreased,moderately decreased,slowly decreased,and increased population density account for 13.3%,30.5%,41.1%,and 15.1%,respectively.In terms of spatial distribution,cities with rapidly decreased population density are mainly distributed in Eastern China.Cities with moderately decreased and slowly decreased population density are mainly distributed in the Central China.Cities with fast inflow of population experience an increase of urban population density,such as Beijing,Shanghai,and Shenzhen.We also found urban population density increased in some small cities with slow development of economy.The population density changes of the five major urban agglomerations are significant.The population density of the core cities in the Beijing-Tianjin-Hebei,Yangtze River Delta,and Pearl River Delta urban agglomerations are slowly decreased or increased population density.The population density of other cities decline faster than that of the core cities.The population density of the core cities in the middle reaches of the Yangtze River and Chengdu-Chongqing urban agglomerations are rapidly decreased or moderately decreased,and the population density of other cities decline more slowly than the core cities.(4)Economic development level,industrial structure,urbanization level,initial population density and macro-policy are the main driving factors of population density change.The level of economic development and the initial population density have a positive role in promoting the decline of population density.The upgrading of industrial structure and the improvement of urbanization level can slow down the decline of population density.In view of the general decline of urban population density in China,the decline of urban population density in China can be slowed down by promoting the upgrading of industrial structure,improving the level of urbanization and controlling the expansion of urban land.At the national level,we must promote land conservation and intensive use,and strengthen farmland protection measures.