Evolutionary trends of urban expansion and its sustainable development: Evidence from 80 representative cities in the belt and road initiative region

Rapid urbanization of the Belt and Road Initiative (BRI) region has undoubtedly led to changes in the scale, form, and pattern of cities to accommodate the expansion of industry, housing, and commerce and to produce sustained impacts on environmental sustainability. However, limited studies have yet to systematically investigate the urban expansion in this area. Based on a systematic research path of “pattern-mode-coordination-sustainability”, this study quantified the urban expansion dynamics of BRI countries and 80 representative cities from 2000 to 2018 using multi-source remote sensing data and the Global Atlas of Urban Expansion. The results show that in terms of dynamic rules, the share of urban lands grew from 0.32 % in 2000 to 0.66 % in 2018 (an increase of 250,600 km2) and is estimated to increase to 1.68 % in 2018–2030. Countries in developing regions (i.e., West Asia, North Africa, and Southeast Asia) are predicted to become the new high-value centers of urban expansion intensity (UEI). The UEI of BRI cities showed a significant developing region orientation and “high in the east and low in the west” distribution pattern but would gradually shift towards a spatially homogeneous and discrete distribution. BRI cities can be divided into four expansion modes (center-periphery, double-winged strip, dual-core cluster, and single-winged mutation expansion), each with a different evolutionary dynamic mechanism. Regarding coordination, there is a great demand for land expansion by population and economic growth in BRI cities. This dependence increased as the city's UEI index rose; when the UEI exceeded 3 %, the dependence became more pronounced. The investigations also showed that the adverse ecological effects of urban land expansion are gradually increasing at the urban scale. Furthermore, the ecological impacts of population growth are usually the strongest for BRI's countries and cities, and the intensity showed a synergistic growth trend with the UEI index. This study provides new insights into the dynamic features of BRI's urban expansion from national to urban scales and historical to future periods, while also contributing new perspectives from the BRI to optimal global land management and sustainable urban development.