Remote sensing-based morphological analysis of core city growth across the globe

The morphology of core city growth can be defined as the area, geometry, and change rate of core city within a specific period. A global analysis of core city growth can help predict future development with respect to different natural and social settings. However, current studies largely focus on limited cities or time series of urban expansion, providing limited insight to assess the status of global sustainable development in urban areas. In this study, we examined the morphological evolution of 2276 cities worldwide from 2003 to 2018 using harmonized nighttime satellite data. We found that during the study period the global core city area increased nearly 52 % with Asia leading the growth (4.5 × 10 5 km 2 ) and North America growing the least (0.8 × 10 5 km 2 ). Based on the morphological characteristics, we further identified six city morphological types: decelerated, intensifying, stable, mature, growing, and shrinking. The decelerated type dominated, followed by the intensifying and shrinking types. Cities falling within the other three patterns accounted for about 10 % of the total. Cities with the stable and mature types grew slowly, mainly found in developed regions such as Europe and North America, while cities with the growing type exhibited a high growth rate and were mostly located in developing regions such as Africa and Asia. Moreover, cities with the shrinking pattern were also found in certain developed regions such as Japan, coinciding with the population decline there. Our analysis of global urban morphology 16 years can provide valuable insights into the variations of global core city growth, which are critical for formulating effective policies to achieve urban sustainability. • Global core city area has increased 52 % from 2003 to 2018. • 54 % of all cities were growing slowly with small initial core city area which were designated as the decelerated morphology. • Cities with slow-growing rate were mainly distributed in developed countries. • Only 7 % of all cities developed with a higher population growth than urban sprawl.