Fractional Vegetation Cover Change and Its Evaluation of Ecological Security in the Typical Vulnerable Ecological Region of Northwest China: Helan Mountains in Ningxia

The well-being of the human race is closely related to the ecological environment. In the past few decades, indicators retrieved from remote sensing data have been increasingly more widely applied to ecological environment evaluation for their advantages of spatial visualization, and remote sensing technology offers important reference to regional ecological environment governance, improvement, and development planning by quickly assessing regional ecological environment quality. Based on Landsat 5/8 images from 1987, 2000, 2007, 2017 and 2020, vegetation coverage (FVC) and remote sensing ecological index (RSEI) were selected to explore the spatial-temporal changes of ecological environment in Helan Mountains, Ningxia, and to analyze the vegetation status and ecological restoration effect before and after the implementation of ecological protection action in Helan Mountains in 2017. The results show that: (1) In general, the vegetation coverage and ecological environment of Helan Mountains in Ningxia had been continuously improved during 1987-2020. The annual average FVC had increased from 31.03% (1987) before the ecological battle to 43.35% (2020) recently, and the RSEI had increased from 32.71% to 50.45%, indicating a significant effect of ecological restoration. (2) The FVC and RSEI were still at low level, and the overall ecological quality in the research area was in ordinary status. The FVC and RSEI of the higher altitude areas in the west and the tourist-intensive areas in the central and southern regions had been obviously degraded, with degradation rates of 12.11% and 8.30%, respectively. (3) The spatial distribution and variation trend of FVC was highly consistent with those of RSEI, and the correlation coefficients are all greater than 0.80. Greenness index has the highest weight in principal component analysis, indicating that the increase of FVC has a positive impact on the ecological environment of Helan Mountains in Ningxia. The results in the present study have important reference significance for the restoration and management of the ecological environment in the area of ecologically fragile area such as Helan Mountains and other similar protected areas.