Megacities serve as global centers for economic,cultural,and high-tech industries.The structural features and population agglomerations are typical traits of urbanization,yet little is known about the morphological fe...Megacities serve as global centers for economic,cultural,and high-tech industries.The structural features and population agglomerations are typical traits of urbanization,yet little is known about the morphological features and expansion patterns of megacities worldwide.Here we examined the spatiotemporal variations of urban land in megalopolises from 2000 to 2020 using the Urban Expansion Intensity Differentiation Index.The fractal features and expansion patterns of megacities were analyzed using the Area-Radius Multi-dimensional Scaling Model.Urban land use efficiency was then evaluated based on the linear relationship between urban land area and population.We found that Southeast Asia and China were the hotspots of urban expansion in megacities from 2000 to 2020,with urban land areas expanding by 3148.32 km^(2)and 5996.26 km^(2),respectively.The morphological features and expansion patterns of megacities exhibited a growing trend towards intensification and compactness,with the average radial dimension increasing from 1.54 to 1.56.The annual decrease in fractal dimensions indicated the integration of inner urban areas.North America and Europe megacities showed a low urban land use efficiency,with a ratio of urban land area to population ranging from 0.89 to 4.11 in 2020.Conversely,South Asia and Africa megacities exhibited a high urban land use efficiency,with the ratios between 0.23 and 0.87.Our results provide information for promoting efficient urban land utilization and sustainable cities.It is proposed to control the scale of urban expansion and to promote balanced development between inner and outer urban areas for achieving resilient and sustainable urban development.展开更多
High-resolution mapping and monitoring of national land use/cover changes contribute significantly to the knowledge of the interaction between human activities and environmental changes.China’s Land Use/cover Dataset...High-resolution mapping and monitoring of national land use/cover changes contribute significantly to the knowledge of the interaction between human activities and environmental changes.China’s Land Use/cover Dataset(CLUD)for 2020 and its dynamic changes in 2015-2020 were developed to extend the CLUD to over 30 years(i.e.,the 1980s to 2020 at 5-year intervals)by integrating remote sensing big data and knowledge-based human-computer interaction interpretation methods.This integrating method for CLUD 2020 improved the efficiency of national land use/cover mapping and the accuracy of land use pattern change detection compared to earlier CLUD products,with an overall accuracy of 95%.The intensity of land use change decreased across China in 2015-2020 compared to 2010-2015,although both characteristics of its spatial changes were similar.The cropland area continued to shrink at national scale in 2015-2020,with two regional hotspots including the widespread conversions from dry land into paddy land in Northeast China and the coexistence of widespread land cultivation and cropland abandonment in Xinjiang of Northwest China.Built-up land area continued to expand in China,showing consistency between 2015-2020 and 2010-2015,in which hotspots transited from the surroundings of coastal megacities to the city surroundings of the central and western zones.For natural land,although the woodland and grassland decreased in 2015-2020,its magnitude expanded compared to 2010-2015.In comparison,the water body area in Qinghai-Tibet Plateau increased significantly under the continuous impact of climate change.These characteristics of land use change were closely related to the development strategy of the top-level design of the 13th Five-Year Plan(2016-2020)(e.g.,ecological civilization construction and high-quality development).展开更多
Humans deeply influence the urbanizing of earth’s surface system in an exacerbating manner across space and time[1].Around the globe,urban land-use/cover changes reflect the intensities of human activities and land s...Humans deeply influence the urbanizing of earth’s surface system in an exacerbating manner across space and time[1].Around the globe,urban land-use/cover changes reflect the intensities of human activities and land shifts from nature or semi-nature lands to man-made–dominated surfaces[2].展开更多
Comparing the city-size distribution at the urban agglomeration（UA） scale is important for understanding the processes of urban development. However, comparative studies of city-size distribution among China＇s thre...Comparing the city-size distribution at the urban agglomeration（UA） scale is important for understanding the processes of urban development. However, comparative studies of city-size distribution among China＇s three largest UAs, the Beijing-Tianjin-Hebei agglomeration（BTHA）, the Yangtze River Delta agglomeration（YRDA）, and the Pearl River Delta agglomeration（PRDA）, remain inadequate due to the limitation of data availability. Therefore, using urban data derived from time-series nighttime light data, the common characteristics and distinctive features of city-size distribution among the three UAs from 1992 to 2015 were compared by the Pareto regression and the rank clock method. We identified two common features. First, the city-size distribution became more even. The Pareto exponents increased by 0.17, 0.12, and 0.01 in the YRDA, BTHA, and PRDA, respectively. Second, the average ranks of small cities ascended, being 0.55, 0.08 and 0.04 in the three UAs, respectively. However, the average ranks of large and medium cities in the three UAs experienced different trajectories, which are closely related to the similarities and differences in the driving forces for the development of UAs. Place-based measures are encouraged to promote a coordinated development among cities of differing sizes in the three UAs.展开更多
基金The Strategic Priority Research Program of Chinese Academy of Sciences,No.XDA20040403,No.XDA23100201。
文摘Megacities serve as global centers for economic,cultural,and high-tech industries.The structural features and population agglomerations are typical traits of urbanization,yet little is known about the morphological features and expansion patterns of megacities worldwide.Here we examined the spatiotemporal variations of urban land in megalopolises from 2000 to 2020 using the Urban Expansion Intensity Differentiation Index.The fractal features and expansion patterns of megacities were analyzed using the Area-Radius Multi-dimensional Scaling Model.Urban land use efficiency was then evaluated based on the linear relationship between urban land area and population.We found that Southeast Asia and China were the hotspots of urban expansion in megacities from 2000 to 2020,with urban land areas expanding by 3148.32 km^(2)and 5996.26 km^(2),respectively.The morphological features and expansion patterns of megacities exhibited a growing trend towards intensification and compactness,with the average radial dimension increasing from 1.54 to 1.56.The annual decrease in fractal dimensions indicated the integration of inner urban areas.North America and Europe megacities showed a low urban land use efficiency,with a ratio of urban land area to population ranging from 0.89 to 4.11 in 2020.Conversely,South Asia and Africa megacities exhibited a high urban land use efficiency,with the ratios between 0.23 and 0.87.Our results provide information for promoting efficient urban land utilization and sustainable cities.It is proposed to control the scale of urban expansion and to promote balanced development between inner and outer urban areas for achieving resilient and sustainable urban development.
基金The Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDA23100201National Key R&D Program of China,No.2018YFC1800103The Second Tibetan Plateau Scientific Expedition and Research Program,No.2019QZKK0608。
文摘High-resolution mapping and monitoring of national land use/cover changes contribute significantly to the knowledge of the interaction between human activities and environmental changes.China’s Land Use/cover Dataset(CLUD)for 2020 and its dynamic changes in 2015-2020 were developed to extend the CLUD to over 30 years(i.e.,the 1980s to 2020 at 5-year intervals)by integrating remote sensing big data and knowledge-based human-computer interaction interpretation methods.This integrating method for CLUD 2020 improved the efficiency of national land use/cover mapping and the accuracy of land use pattern change detection compared to earlier CLUD products,with an overall accuracy of 95%.The intensity of land use change decreased across China in 2015-2020 compared to 2010-2015,although both characteristics of its spatial changes were similar.The cropland area continued to shrink at national scale in 2015-2020,with two regional hotspots including the widespread conversions from dry land into paddy land in Northeast China and the coexistence of widespread land cultivation and cropland abandonment in Xinjiang of Northwest China.Built-up land area continued to expand in China,showing consistency between 2015-2020 and 2010-2015,in which hotspots transited from the surroundings of coastal megacities to the city surroundings of the central and western zones.For natural land,although the woodland and grassland decreased in 2015-2020,its magnitude expanded compared to 2010-2015.In comparison,the water body area in Qinghai-Tibet Plateau increased significantly under the continuous impact of climate change.These characteristics of land use change were closely related to the development strategy of the top-level design of the 13th Five-Year Plan(2016-2020)(e.g.,ecological civilization construction and high-quality development).
基金supported by the Special Project of Global Space Remote Sensing Information Submission and Annual Report from the Ministry of Science and Technology(1061302600001)the National Natural Science Foundation of China(41871343)+1 种基金the Strategic Priority Research Program(A)of the Chinese Academy of Sciences(XDA23100201)the Second Tibetan Plateau Scientific Expedition(2019QZKK0608)。
文摘Humans deeply influence the urbanizing of earth’s surface system in an exacerbating manner across space and time[1].Around the globe,urban land-use/cover changes reflect the intensities of human activities and land shifts from nature or semi-nature lands to man-made–dominated surfaces[2].
基金National Natural Science Foundation of China,No.41621061,No.41501092 Talents Training Program from the Beijing Municipal Commission of Education No.201500002012G058
文摘Comparing the city-size distribution at the urban agglomeration（UA） scale is important for understanding the processes of urban development. However, comparative studies of city-size distribution among China＇s three largest UAs, the Beijing-Tianjin-Hebei agglomeration（BTHA）, the Yangtze River Delta agglomeration（YRDA）, and the Pearl River Delta agglomeration（PRDA）, remain inadequate due to the limitation of data availability. Therefore, using urban data derived from time-series nighttime light data, the common characteristics and distinctive features of city-size distribution among the three UAs from 1992 to 2015 were compared by the Pareto regression and the rank clock method. We identified two common features. First, the city-size distribution became more even. The Pareto exponents increased by 0.17, 0.12, and 0.01 in the YRDA, BTHA, and PRDA, respectively. Second, the average ranks of small cities ascended, being 0.55, 0.08 and 0.04 in the three UAs, respectively. However, the average ranks of large and medium cities in the three UAs experienced different trajectories, which are closely related to the similarities and differences in the driving forces for the development of UAs. Place-based measures are encouraged to promote a coordinated development among cities of differing sizes in the three UAs.
