Desertification in the Mu Us Sandy Land in China: Response to climate change and human activity from 2000 to 2020

China is a country largely affected by desertification. The main purpose of this article is to analyze interannual and seasonal changes in fractional vegetation cover (FVC) in the Mu Us Sandy Land (MUSL). It uses fused remote sensing data to quantitatively analyze the response of FVC to climate change and human activities. The results showed that desertification in the MUSL had improved over the past 20 years. Grade V desertification decreased from more than 60% in 2000 to about 15% in 2020. In some years, degradation appeared to be affected by climate factors and human activity, especially in the northwestern portion of the study area. The FVC in summer was slightly higher than that in autumn and far higher than recorded in spring and winter. Spatially, the northwestern and central parts of the study area were unstable, with high coefficients of variation. FVC gradually increased from northwest to southeast, and areas with the fastest increase in FVC were concentrated along the eastern and southern edges of the study area. The correlations between FVC and precipitation and dryness were slightly positive, but the correlation between FVC and temperature showed regional differences. The increase of population density is not a key factor limiting the growth of vegetation; the policy of “grazing prohibition, grazing rest, and rotational grazing” has allowed the restoration of vegetation; and afforestation is an effective way to promote the increase in FVC.