张掖市生态环境质量评价及其影响因素分析

Evaluation of ecological environment quality and its driving factors in Zhangye City

关键词:  张掖市  土地利用  生态环境质量  地理探测器

Key words:  Zhangye City  land use  ecological environment quality  geodetector

摘要:

张掖市是河西走廊地区典型的绿洲型城市，降水稀少、气候干旱，生态环境较为脆弱。文章基于 1990—2020 年的土地利用数据，利用区域生态环境质量指数 （EV） 模型对张掖市生态环境质量空间分布和变化情况进行评价，并借助地理探测器对影响生态环境质量变化的因素进行分析。结果表明：（1） 1990—2020 年张掖市耕地面积和建设用地面积持续增加，未利用地和草地主要转换为耕地； （2） 1990—2020年，张掖市区域生态环境质量指数维持在0.2779—0.2807，呈现出“先下降，再上升” 的变化特征，生态环境质量整体较为稳定且有好转趋势；（3） 张掖市生态环境质量变化受社会经济因素与自然因素的共同驱动，并以社会经济因素为主导，根据解释力排序为：人口密度变化＞国内生产总值 （GDP） 变化＞高程＞粮食产量变化。

Abstract:

Background, aim, and scope Evaluation of ecological environment quality plays an important role in formulating environmental protection policies and land resource utilization plans. Based on specific indicator systems and quality standards, ecological environment quality evaluation refers to the assessment of the overall condition of a regional ecological environment and its impacts. Zhangye City is a typical oasis city located in the Hexi Corridor of northwest China, characterized by drastic land-use transformations and a fragile ecological environment. Although numerous studies have focused on land-use change or ecological environment quality assessment in Zhangye City, a comprehensive study on the spatiotemporal changes in ecological environment quality and their driving factors based on the geodetector is still lacking. Therefore, this study takes Zhangye City as the study area, evaluates ecological environment quality and analyzes its driving factors using the ecological environment quality index (EV) model and the geodetector, aiming to provide a scientific basis for land resource utilization and ecological environment protection in Zhangye City. Materials and methods Based on land-use data from seven periods (1990, 1995, 2000, 2005, 2010, 2015, and 2020), this study evaluates the spatial distribution and temporal changes in ecological environment quality in Zhangye City using the ecological environment quality index assessment. The driving factors influencing changes in ecological environment quality are further analyzed using the geodetector. Results (1) The areas of farmland and construction land in Zhangye City increased continuously from 1990 to 2020, with the conversion of unused land and grassland to farmland being the dominant transformation type. (2) The regional ecological environment quality index in Zhangye City remained relatively stable, ranging from 0.2779 to 0.2807 during 1990—2020. Land transformation types with higher contribution rates to improvements in ecological environment quality mainly included the conversion of sandy land and Gobi land to dry farmland. (3) Changes in ecological environment quality in Zhangye City resulted from the combined effects of socioeconomic and natural factors, with socioeconomic factors playing a dominant role. According to explanatory power, the driving factors were ranked as follows: change in population density > change in GDP (Gross Domestic Product) > elevation > change in grain yield. Discussion (1) Changes in regional ecological environment quality are closely associated with land-use transformations. Spatially, areas with high ecological environment quality in Zhangye City are mainly distributed in the Qilian Mountains in the southwest, where forest land and grassland dominate, whereas areas with low ecological environment quality are primarily located in the northeastern plains, dominated by unused land. (2) From 1990 to 2020, the ecological environment quality of Zhangye City was higher than the average level of the Hexi Corridor. (3) Changes in ecological environment quality in Zhangye City during 1990—2020 were driven by multiple factors, and the interaction mechanisms among these factors were complex. Conclusions The spatial distribution pattern of ecological environment quality in Zhangye City remained relatively stable from 1990 to 2020, with an overall “V-shaped” temporal trend. Changes in ecological environment quality were jointly driven by socioeconomic and natural factors, with socioeconomic factors exerting a dominant influence. Recommendations and perspectives The ecological environment quality index assessment effectively reflects the relationship between regional land use and ecological environment quality. When land-use types are transformed from unused land to farmland, large areas without vegetation cover are converted into vegetated land, resulting in an increase in the ecological environment quality index. However, it should also be noted that the expansion of farmland and irrational land-use practices may still lead to a decline in ecological environment quality, and may even result in the reversion of farmland to Gobi land and sandy land.