基于GEE和遥感大数据的1986—2015年全球城镇用地扩张占用水体时空特征

Spatial and Temporal Characteristics of Water Bodies Occupied by Global Urban Land Expansion from 1986 to 2015 Based on GEE and Remote Sensing Big Data

以全球年度城市动态数据(GAUD)和全球地表水动态数据集(GSW)为基础数据,利用Google Earth Engine(GEE)解析了1986—2015年全球城镇用地扩张占用永久性和季节性水体的时空分布特征。研究发现:30 a间全球城镇用地扩张直接占用水体的面积为1033.2 km^(2),其中包括季节性水体711.7 km^(2)和永久性水体321.5 km^(2),呈现先增加后降低的变化趋势。亚洲是城镇用地扩张占用水体面积最多的大洲,其次是北美洲和欧洲,占用水体的面积分别为799.4 km^(2)、122.5 km^(2)和61.1 km^(2)。欧洲是唯一以占用永久性水体为主的大洲。陆地面积排名前十的国家中,中国、美国和印度是城镇用地扩张占用水体面积最多的国家,占用水体的面积分别为573.1 km^(2)、109.6 km^(2)和24 km^(2)。以占用永久性水体为主的国家是俄罗斯和阿尔及利亚。尽管世界各国在水资源保护方面做出了巨大努力,但实现联合国可持续发展目标背景下,需防控更多的水体因城镇用地扩张而消失。

Due to the increase of global population and economic development,the water body inside of the cities and its surroundings has been continuously occupied since the 1970s,causing serious damage to ecological environment.Thus,it is very important to estimate the condition of water body occupied by urban land expansion around the world.With the data processing and analysis functions of the Google Earth Engine cloud platform(GEE),we explored the temporal and spatial characteristics of permanent and seasonal water body occupied by global urban land expansion from 1986 to 2015 using the dataset of global annual urban dynamics(GAUD)and global surface water(GSW).Our objective can be characterized by:1)Describing the spatial distribution pattern of water body occupied by urban land expansion on a global scale;2)Analyzing the characteristics of changes in the water area occupied by urban land expansion over time on global,continental,and national scales;3)Discussing the potential ecological effects of water body occupied by urban land expansion and the suggestions to solve this problem in China.We find that water areas occupied by global urban land expansion increase firstly but decrease then,representing 1033.2 km^(2) over 30 years,in which the seasonal water body is 711.7 km^(2) and the permanent water body is 321.5 km^(2).Asia is the most significant continent with urban land expansion among the six continents,followed by North America and Europe,which accounts for 799.4 km^(2),122.5 km^(2) and 61.1 km^(2) respectively.Meanwhile,Europe is the only continent which mainly dominates by permanent water body while Russia and Algeria are the counties dominating by that.Especially,China,the United States and India are the countries with the most serious water body occupied by urban land expansion,amounting to 573.1 km^(2),109.6 km^(2) and 24 km^(2) respectively.Many ecological and environmental issues can be attributed to the occupation of water body generated by urban land expansion,including:declining of wetland quality,increasing the risk of sandstorms,threatening the safety of drinking water and aggravating the urban heat island effect,etc.Although countries have made great efforts to protect water resources,the results of this study show that the problem of water bodies being occupied by urban expansion is still serious.Under the special national conditions and policy background,this problem appears to be particularly serious in China.To prevent more water bodies from being encroached by urban land expansion,feasible suggestions China could adopt are as follows:1)Continuously paying attention to the expansion of urban land across the country;2)Scientifically planning the layout of land use;and 3)Actively promoting wider international cooperation.