Expansion of megacities in five central Asian countries along “One Belt and One Road” routes (2000—2018)

The five central Asian countries are important locations in the “One Belt and One Road” development strategy proposed by China in 2013．Examination of urban expansion in these five central Asian countries is helpful to promote cooperation and development between countries of the “One Belt and One Road”．Normalized difference impervious index (NDII) was employed to extract from three long-time series of Landsat TM/ETM+/OLI imagery (acquired in the 2000, 2010, 2018) impervious surfaces for the five central Asian countries．Urban expansion intensity, speed and compactness were analyzed．Urban expansion over the past 18 years at 8.75% was the largest in Astana, at 1.02% was the slowest in Bishkek．Urban expansion at Nursultan, Toshkent and Ashgabat decelerated, but at Bishkek and Dushanbe accelerated．For overall space, Nursultan demonstrated a very compact expansion, but at Bishkek, Toshkent and Dushanbe, urban space showed initial expansion, followed by compaction．Ashgabat urban space development was characterized by compactness followed by stability．The gravity of capital from 2000 to 2018 in Nursultan, Bishkek and Dushanbe gradually moved southwest, in Toshkent and Ashgabat gradually moved southeast．Population and economic development was found to have different effect on urban expansion．This study has theoretical and practical significance for urbanization in the five central Asian countries of the “One Belt and One Road” strategy．．