Assessment of aeolian desertification trends from 1975ʹs to 2005ʹs in the watershed of the Longyangxia Reservoir in the upper reaches of Chinaʹs Yellow River

Global climate change will affect the ecology and environment of the Qinghai–Tibet Plateau, thus increasing attention is being paid to the aeolian desertification that is occurring in the watershed that supplies the Longyangxia Reservoir in the upper reaches of Chinaʹs Yellow River. We must assess the aeolian desertification trends before developing a plan to restore the regionʹs degraded eco-environment. In this study, land suffered from aeolian desertification was classified into four levels (slight, moderate, severe, and extremely severe) using a series of indices. Interpretation of Landsat MSS and TM data from 1975ʹs, 1989ʹs, and 2005ʹs was used to establish databases of aeolian desertified land at these three times. We then derived the aeolian desertification trends during the study period by overlaying the consecutive databases, and we analyzed the driving factors responsible for the observed aeolian desertification. The results show a total of 1,721,478.02 ha of aeolian desertified land in 2005ʹs, accounting for 13% of the regionʹs total area. From 1975ʹs to 1989ʹs, the area of aeolian desertified land increased by 229,307.26 ha, which represents a 15% increase compared to the 1975ʹs area; and from 1989ʹs to 2005ʹs, the area of aeolian desertified land decreased by 19,079.87 ha, which represents a 1% decrease compared to the 1989ʹs area. The main driving factors responsible for this increased aeolian desertification were climate factors (high wind velocity and an increase in annual temperature, combined with low precipitation and high evaporation) as well as unsustainable human activities and inappropriate policy measures. A series of key national projects initiated to combat degradation of the study areaʹs eco-environment led to a decrease of aeolian desertified land through obvious restoration of vegetation.