Sand-dust storms in and around the Ordos Plateau of China as influenced by land use change and desertification

The occurrence of sand-dust storms induced by wind erosion is a process that accelerates land degradation and can also be considered as an indicator of desertification. Thus, it is of significance both in theory and in practice to reveal the interaction between these two phenomena. Based on data from the Ordos Plateau and its surrounding areas, a study has been made of the effect of land degradation and land use changes on sand-dust storms. In this study, we report a non-linear relationship between sand-dust storm frequency and the index of land degradation (Id), which is defined as the percentage of the area of total land that is desertified. Using this non-linear relationship, a threshold at Id = 30% is established such that, when Id < 30% sand-dust storm frequency does not change with increasing Id but when Id > 30%, sand-dust storm frequency increases rapidly. This existence of such a threshold means that sand-dust storm frequency would increase abruptly when the human-induced Id exceeds 30%. The time series of annual number of sand-dust storm days in the neighbouring area has been compared to the time series in the annual number of strong wind days and the time series in the area of cultivated land in Yikezhao Meng, and a multi-regression equation has been established. Based on the equation, the relative contributions of the variations in land use and in annual number of strong wind days to the variation in annual number of sand-dust storm days have been estimated as 59.7% and 40.3%, respectively, indicating that the frequency of sand-dust storms may be effectively decreased by reducing the area of cultivated land and restoring the natural steppe vegetation in ecologically fragile areas in arid and semi-arid climates.