Tempo-spatial changes of ecological vulnerability in the arid area based on ordered weighted average model

Ecological environment in the arid areas of Northwest China is very vulnerable. Ecological vulnerability is considered to be one of the important indicators to measure the status and evolutions of the regional ecological environment and has become a key measure in the study of ecological change. However, studies on the ecological vulnerability in the whole arid areas of Northwest China on the county scale are currently sparse. Here, according to vegetation, land use type, topography, climate and socio-economic data, we present the spatial and temporal evolution of ecological vulnerability in the arid areas of Northwest China over the period 2000-2018 by structuring a "pressure (P)-sensitivity (S)-restoration (R)" ecological vulnerability evaluation index system and using an ordered weighted average (OWA) model. Our results suggested that the overall ecological vulnerability in the arid areas of Northwest China was dominated by the severe level from 2000 to 2018 with an average multiyear ecological vulnerability index of 0.48, which appeared a slight downward trend with the implementation of ecological restoration measures. Ecological vulnerability exhibited a significant "stepped" differentiation feature, and the eastern and western regions were markedly lower than that of the central region. Gravity center of the ecological vulnerability index has a significant spatial difference, which developed in the shape of "Z" direction between Heshuo county and Tuokexun county. Our study revealed the dynamic changes of ecological vulnerability at the county scale and provided decision-making information for the formulation of targeted ecological vulnerability management measures. Under the background of climate change and the new normal of social economy, the dynamic monitoring of ecological vulnerability and effective identification of vulnerability factors still require in-depth research.