Spatial And Temporal Differences And Ecological Effects Of Urbanization Quality In Pearl River Delta Urban Agglomeration

Since the reform and opening up,China ’ s urbanization process has entered a new stage,and the urbanization rate has increased rapidly from 17.92 % in 1978 to 60.60 % in 2019.With the rapid expansion of China’s urbanization process,a series of internal and external problems have also been caused,such as unbalanced development among cities and lagging development of small and medium-sized cities.These problems are particularly prominent in the economically developed Pearl River Delta urban agglomeration,which restrict the overall improvement of the urbanization level of urban agglomeration.Therefore,it is necessary to study the spatiotemporal differences of urbanization quality in order to promote the coordinated development of urbanization in the Pearl River Delta urban agglomeration.External such as early spread cake development mode,bring the rapid expansion of urban scale,but also change the type of regional land use,causing the destruction of the structure and function of the surrounding ecological system.Therefore,this paper further discusses the ecological effect of urbanization quality stage,in order to promote the sustainable development of urban agglomeration urbanization and ecological environment.Based on the statistical yearbook data of nine major cities in the Pearl River Delta from2000 to 2018,Globe Land30 land cover data,administrative divisions and DEM data,this study explores the spatial and temporal differences of urbanization quality and the ecological effects of urbanization quality improvement in urban agglomerations.Firstly,based on the concepts and theories related to urbanization,starting from four dimensions of economy,society,population and space,the WBS work breakdown structure method and entropy method are adopted to construct the urbanization quality measurement system.Secondly,based on the evaluation system,the time series changes and spatial differences of the four suburbanization and comprehensive urbanization quality scores were analyzed through standard deviation,coefficient of variation and GIS spatial analysis.Thirdly,landscape pattern index,ecological service value evaluation and ecological risk index were used to explore the landscape ecological effect,ecosystem service value change and ecological risk effect brought by the improvement of urbanization quality in different development stages.Finally,according to the spatiotemporal difference of urbanization quality and the change of ecological effect,the strategy of coordinated development of urbanization and sustainable development of urbanization and ecological environment is proposed,which can provide reference for promoting coordinated and healthy development of the whole urban agglomeration.The results show that:(1)From 2000 to 2018,the quality of economic,social,population and spatial urbanization in the Pearl River Delta urban agglomeration shows a positive growth trend,but the gap between cities is also gradually widening.The spatial differentiation of the four sub-urbanization quality development stages is significant,with a pattern of higher quality in the central part of the Pearl River Delta and lower quality in the surrounding area in the later stage.(2)From 2000 to 2018,the comprehensive urbanization quality of urban agglomerations increased steadily,and the regional gap continued to increase,showing the characteristics of uncoordinated development.The overall comprehensive urbanization quality is divided into two echelons,and the urbanization quality gap between the first and second echelons and within the second echelons is gradually widening with the passage of time.In space,it is high in the middle of the Pearl River Delta and gradually decreases to the surrounding "convex" pattern.(3)In terms of landscape ecological effect,with the improvement of urbanization quality development stage,human activities have frequently transformed bare land and wetland.Meanwhile,the degree of fragmentation of cultivated land,grassland and artificial surface has increased,showing a local development trend,dividing the relationship between habitat patches and reducing the quality of regional habitat.The richness of regional landscape land use types increased,and the landscape types showed a trend of complexity and diversity,which was conducive to the improvement of species and ecosystem diversity.At the same time,the landscape shape tends to change regularly,which is easy to cause soil erosion disaster at the edge of patches.(4)In terms of the change of ecological service value,the overall ecological service value of the Pearl River Delta urban agglomeration showed a declining trend over time,and the decline increased significantly in the later period.With the improvement of urbanization quality,the total ecological service value and ecosystem service function declined at each stage.(5)In terms of ecological risk effect,as time goes by,the area proportion of higher and higher risk zones increases,and the spatial expansion trend is from the central part of the urban agglomeration to the surrounding cities.With the improvement of urbanization quality development stage,the overall ecological risk index of each stage increases,the ecological risk level remains unchanged or increases,and the regional ecological environment has a tendency to deteriorate.(6)According to the characteristics and problems of spatial and temporal differences of urbanization quality,countermeasures for coordinated development of urbanization are put forward from the perspectives of economy,society,population and space.In view of the ecological effect of the improvement of urbanization quality stage,this paper puts forward suggestions on the sustainable development of urbanization and ecological environment from the aspects of land planning,utilization and control.