“一带一路”沿线地区城市扩张和形态变化分析

尽管越来越多的人认识到“一带一路”沿线各国的城市化进程对其经济、政治和环境系统所起的重要作用,但对监测区域范围内城市扩张和形态变化的比较研究却极为有限。基于欧空局气候变化倡议项目最新发布的1992—2015年300 m分辨率的全球土地覆盖数据集、1992—2012年DMSP/OLS夜间灯光数据和2000—2015年LandScan人口数据,本文首先分析了1992—2015年“一带一路”陆域城市用地增长的空间格局和十大分区城市用地面积的动态。其次,通过分析3个时间点（1992年、2003年和2015年）上同心环内城市用地密度的时空变化,量化了“一带一路”沿线80个城市的扩张和形态变化。最后采用3种统计模型（线性、幂律和指数函数模型）来分析城市用地面积、加权灯光面积和城市人口之间的长期关系。结果显示,“一带一路”陆域城市用地面积占土地总面积的比例从1992年的0.24%上升至2015年的0.56%,并且非洲和亚洲的发展中国家是“一带一路”监测区域城市化的主要贡献者。同心环内城市用地密度从城市中心到城市边缘呈递减趋势,且城市间的空间分布完全不同。中国、欧洲、非洲、西亚、东南亚和印度6个分区人口数超过100万的城市间比较显示,除了中国城市形态变得分散,其他分区城市形态总体变得紧凑。分析结果也显示,夜间灯光信号所反映的城市经济活力和城市人口分布趋势在不同程度上影响城市空间扩张和形态变化。

Urban expansion and form changes along the Belt and Road Initiative

Although more and more people realize the important role of the urbanization process on the economic, political and environmental systems along the Belt and Road, the study on urban expansion and form changes is still limited. Based on the latest 300 m resolution global land cover dataset from 1992 to 2015 released by the ESA Climate Change Initiative project, DMSP/OLS night lighting data from 1992 to 2012, and LandScan population data from 2000 to 2015, in this paper we first analyzed the spatial pattern of urban land growth and dynamics in the ten major sub-regions along the Belt and Road from 1992 to 2015. Then, by analyzing the spatial and temporal changes of urban land density in concentric rings in 1992, 2003 and 2015, the expansion and form changes of 80 cities along the Belt and Road were quantified. Finally, the long-term relationships between urban land area, weighted lighting area and urban population were quantified by using three statistical models, including linear, power-law and exponential function models. The results show that the urban land area along the Belt and Road increased from 0.24% in 1992 to 0.56% in 2015, and developing countries in Africa and Asia are major contributors. The density of urban land in the concentric rings is decreasing from the city center to the urban fringe, and the spatial distribution between cities is completely different. Comparisons among cities in China, Europe, Africa, West Asia, Southeast Asia, and India with populations of more than one million, show that, in addition to the decentralization of China's urban form, the overall urban form of other sub-regions became compact. Further analysis results show that the urban economic vitality and urban population distribution trends will affect the urban spatial expansion and form changes at different levels.