干旱半干旱区城市生态效率时空演变及区域差异分析

研究西北干旱半干旱区城市生态效率,对其经济、资源、环境的协调统一以及生态文明建设的推进具有重要的现实意义。以西北干旱半干旱区38个城市为研究对象,运用三阶段DEA方法客观地测度了各城市2005—2016年生态效率,同时运用ESDA方法全面分析了生态效率的区域差异。结果显示:干旱半干旱区城市生态效率普遍较低,并呈现正向全局空间自相关关系;热点区域主要以乌鲁木齐、克拉玛依等为中心,冷点区域主要以平凉、固原等为中心,热点区域数量呈现先增后减再增的N形变动趋势,冷点区域数量则呈现先减后增再减的倒N形变动趋势。

Temporal and spatial evolution and regional differenceanalysis of urban ecological efficiency in arid and semiaridareas

In recent years,the arid and semiarid regions innorthwest China,including the Xinjiang Uygur Autonomous Region,Inner MongoliaAutonomous Region,Ningxia Hui Autonomous Region,Shaanxi Province,QinghaiProvince,and Gansu Province,have undergone rapid development.However,thefragile ecosystems in these areas are facing greater pressure and the conflictbetween economic development,resources,and the environment is becomingincreasingly prominent due to the extensive economic development model that hasnot yet been fundamentally modified.Eco-efficiency is an effective tool formeasuring the degree of coordination of economic,resource,and environmentalbenefits.In this study,we used the three-stage DEA method to measure eco-efficiency,andthus overcome the effects of external environmental variables and randomfactors on eco-efficiency to obtain more accurate and reliable eco-efficiencyvalues.Meanwhile,we considered 38 cities in 6 provinces in the arid andsemiarid regions of northwest China as research objects and used urban paneldata from 2005 to 2016 to analyze the regional eco-efficiency.Therefore,thedifferences and spatial correlation characteristics of eco-efficiency levelsamong cities could be depicted and described in a more detailed manner.Theresults are described as follows: (1) After eliminating the effects of externalenvironmental variables and random factors,the eco-efficiency level of eachcity changed significantly.The average technical efficiency dropped from 0.65to 0.57,representing a decrease of 12.3%.Theaverage pure technical efficiency increased from 0.91 to 0.95,showing anincrease of 4.4%,and the average scale efficiency decreased from 0.72 to 0.59,indicatinga decrease of 18.1%.These results indicate that external environmentalvariables and random factors have a great effect on eco-efficiency and that itis reasonable and necessary to use the three-stage DEA method to analyze eco-efficiency.(2)In 38 cities,those with medium efficiency and greater accounted for 39% of thetotal,including 15 cities such as Urumqi,Karamay,and Ordos,while those with lowefficiency accounted for 61% of the total,including 23 cities such as Pingliangand Guyuan.These results show that the level of eco-efficiency in the arid andsemiarid areas of northwest China is generally low and that there aresignificant urban differences and imbalances.(3) The global Moran’s I index was positive andincreased yearly,thus indicating that the spatial distribution of eco-efficiencyexhibits increasingly significant positive autocorrelations.The local Getis Ord Gi^* results showthat the distribution areas of cold spots and hot spots of eco-efficiency weremostly the same as those of low efficiency,medium efficiency,and above.Theseresults indicate that urban eco-efficiency has an external driving effect andcities with prominent geographical advantages and perfect ecological managementlevels have high eco-efficiency,which can also promote the improvement of eco-efficiencyof neighboring cities and vice versa.This study compensates for the relativeshortage of studies of eco-efficiency for cities in the arid and semiaridregions of northwest China.The accurate measurements of the value of eco-efficiencyand detailed analyses of the differences and the spatial correlationcharacteristics of eco-efficiency of the cities in this region enhance theobjective understanding of eco-efficiency in the arid and semiarid regions ofnorthwest China,and thus provide new empirical evidence for general improvementin regional eco-efficiency.