基于GIS的长江口海域生态系统脆弱性综合评价

气候变化、富营养化、生境破碎等是全球普遍面临的生态问题,科学评估生态系统外部压力及其弹性力,对生态系统管理和生态修复具有重要的指导意义。使用空间主成分分析(SPCA)和层次分析法(AHP)构建评价指标体系,结合地理信息系统软件,对长江口海域生态环境脆弱性进行综合评价,并根据生态环境脆弱性指数(EVI)值,将研究区生态环境脆弱性分为5级:微度脆弱(0.5)、轻度脆弱(0.5—0.8)、中度脆弱(0.8—1.0)、重度脆弱(1.0—1.2)、极度脆弱(1.2—1.5)。结果表明:空间尺度上,长江口口门内生态环境脆弱度最高,生态环境脆弱度从口门内向口门外呈显著的降低趋势,近五年,口门内极度脆弱区空间分布南移;评估区域内,约2000 km~2的极度脆弱区发生了转变,极度脆弱区、重度脆弱区面积占比分别下降了7%和5%,长江口海域生态环境脆弱性明显好转。总体上,近年来大量陆源污染物输入以及生态系统结构变化,是导致长江口生态环境脆弱度较高的重要因素。

Integrated assessment of marine ecological vulnerability in the Yangtze River Estuary using GIS

Climate change, eutrophication, and habitat fragmentation are ubiquitous ecological problems in the world. It is important to conduct scientific assessment of the external pressure and the resilience of ecosystems for the ecological management and restoration. In the case of the Yangtze River Estuary, as the end of the basin, huge amounts of pollutants were carried into the area, which resulted in the degeneration of the ecosystem during the past decades. However, little is known about the tendency of ecological vulnerability in this area under the effects of human activities and climate change. Consequently, the ecological vulnerability in the Yangtze River Estuary was assessed using geographic information system (GIS) software combined with spatial principal component analysis (SPCA). An analytical hierarchy process (AHP) was used to determine the evaluation factor weightings. According to the ecological vulnerability index (EVI) values, the eco-environmental vulnerabilities of the study area were classified into five levels:potential (< 0.5), light (0.5-0.8), moderate (0.8-1.0), heavy (1.0-1.2) and very heavy (1.2-1.5). The results showed that the inner mouth area of the Yangtze River Estuary was the most vulnerable. There was a significant decrease tendency in EVI from the inside to the outside of the mouth. The spatial distribution of the very heavy vulnerable areas within the mouth has shifted southward in the last five years. The extremely vulnerable area of about 2000 km² has changed in the assessment area with extremely vulnerable area decreased by 7% and severely vulnerable area decreased by 5%. One the other hand, the ecological environment status out of the Yangtze River Estuary has obviously improved from 2013-2017. In general, the input of large amount of land-based pollutants and the instability of the ecosystem caused by human activity were the main factors for the high vulnerability of the Yangtze River Estuary.