Desertification affecting the Tibetan Plateau between 1971-2015: viewed from a climate perspective

Our understanding of desertification on the Tibetan Plateau (TP) is limited. This study aims to fill the knowledge gap by examining desertification and the underlying climatic factors between 1971-2015 on the TP using a dynamic vegetation model and observation-based gridded climate data. Four factors including precipitation, days with above the threshold wind, simulated vegetation fractional plant coverage and soil moisture (SM) in 0-40 cm depth are employed for the spatiotemporal desertification analyses. Simulated plant functional types and SM are evaluated against the observations. By referencing the existing desertification maps in 1977, 1990, 2000, 2010, and 2015, the thresholds of the four factors are determined, and the temporally continuous annual areas of four types of desertification are reconstructed. The Qaidam Basin and Ngari Desert are successfully identified by the above approach. The reduction of total desertification since 2000 is also consistent with national desertification surveys. Climate variation exerts the dominant control on desertification on the TP where population density is low, of which precipitation is the most important climate factor. Moderate but consecutive drought events correspond to the greatest desertification. During 1971-2015, the average total desertification area is 418,329 km(2); among the four types of desertification, moderate desertification occupies the largest area (253,088 km(2)), followed by light desertification (105,583 km(2)) and extremely severe desertification (30,019 km(2)); severe desertification has the least coverage (17,597 km(2)). This approach can also be applied in the other regions given sufficient meteorological and ecological data.