Study On The Spatial Differentiation Between Area With High-density Population Aggregation And Urban Built-up Area In China

Urbanization development faces the dual challenges of scare land resources and sustained urban population growth in current China.How to promote the compact urban devolopment and improve the landuse efficiency is one of the problems to be solved in the future.In the past two decades,the speed of landscape urbanization has doubled that of population urbanization.Inefficient land expansion is more and more,which is often interpreted as urban sprawl.Thus,studing on the spatial distribution and development of physical urban area defined from the perspective of population aggregation(area with high-density population aggregation,AHPA),and on the spatial difference between AHPA and urban built-up area(UA),is of great significance to objectively reflect the real urban development,formulate differentiated urbanization development policy and promote comact urban development.We extrated AHPA of China’s mainland in 1990,2000 and 2010,taking the population density of 1500 people per square kilometer and the population size of 60,000 people as the standard,based on population density raster data.We analyzed the spatial distribution,spatiotemporal changes and demographic characteristics of AHPA.Then,we compared the changes of AHPA and UA in cities from 1900 to 2000 and from 2000 to 2010,and identified the driving mechanisms behind their expansions.Probabilistic forecasts of urban have also been developed to explore its population capacity in accommodating urban population growth.Our results show that:(1)AHPA could not be found in all Chinese cities,although AHPA was identified by the minimum population standard of center towns where the government of countylevel city located in China.More than 20% of the studied cities could not found AHPA from 1990 to 2010.The area of AHPA was declined in around 10% of the studied cities,and it has continued to expand over the past twenty years in nearly 60% of the studied cities.(2)There is spatial differentiation of variation characteristics between AHPA and UA.On the one hand,AHPA expanded with UA growth in more than 60% of the studied cities,and 80% of them had more AHPA growth than UA.On the other hand,UA growth was accompanied with no AHPA or AHPA reduction in over 20% of the studied cities,and the proportion of them was increasing with time.(3)Demographic urbanization rate initail and change contributed differently to the area change of AHPA and UA at the city level from 1990 to 2010.The greater the intial and change of demographic urbanization rate,the faster AHPA expanded,but it has no sigificant impact on the development of UA.GDP change and initial population size also contributed differently to the area change of AHPA and UA from 2000 to 2010.(4)Densification of the existing city area in 2017 alone is likely to accommodate at least 65% of the predicted urban population in 2050,while future urban land expansion at the past speed is highly likely to result in urban sprawl.These results show that the aggregation of high-density population and the expansion of UA are spatially different,driven by different factors.They can better inform optimized future urban development policy and planning at regional and national scale,and enable tailored and spatially-explicit policy-making at the local level.