Evaluation and correlation analysis of spatio-temporal changes of ecological vulnerability based on VSD model: A case in Suzhou section, Grand Canal of China

Ecosystems are closely related to the external environment, both human and natural factors will affect the ecosystem continuously. Ecological vulnerability research can grasp health of regional ecosystem, which is an important basis for regional ecological environmental restoration and planning and governance. It is necessary to conduct research on ecological vulnerability to effectively comprehend the health of the ecosystem. Many theories and methods were proposed to carry out such research work, but few researches will consider the three factors of humanity, nature, and society at the same time. For the purpose of understanding the real situation of canal ecological vulnerability in time, the evaluation index system of ecological vulnerability was established by Vulnerability-Scoping-Diagram（VSD） model based on Suzhou section of the Grand Canal of China. What′s more, founded on grid evaluation unit, the spatial overlay analysis was used to calculate the ecological vulnerability and then to reveal the spatio-temporal distribution pattern and evolution trend of ecological vulnerability combined with analytic hierarchy process（AHP）-entropy weight method and remote sensing（RS）-geographic information system（GIS） technology. Through comprehensive evaluation and correlation analysis of ecological vulnerability, the results showed that:（1） from 2008 to 2018, the ecological vulnerability of the study area was mainly potentially vulnerable and slightly vulnerable with the total proportion increasing from 62.63% to 68.79%, while the proportion of very vulnerable areas and extremely vulnerable areas was relatively small with the total proportion decreasing from 22.45% to 15.61%;（2） The ecological restoration of the study area was favorable. According to the temporal and spatial evolution trend, the study area was divided into ecological restoration area, ecological flat area and ecological degradation area. The ecological restoration rate was 37.09%, the ecological flat rate is 37.93%, and the ecological degradation rate was 24.89%;（3） The ecological restoration area and the ecological degradation area were divided, each including four grade areas, of which the ecological restoration area was mainly Grade I restoration area, accounting for 13.31%; The ecological degradation areas were mainly Grade I and Grade II degradation areas, accounting for 18.80% in total, while Grade IV degradation areas accounted for only 1.50%. As human and social factors have a greater im