Historical settlement abandonment in the middle Hexi Corridor linked to human-induced desertification

Abstract

Understanding past human-environment interactions over a long time-scale offers an analogue to predict, adapt and mitigate the environmental issues caused by global change and human activities in the future. The transient existence of historical cities from arid northern China can provide a valuable reference for this issue. In this study, we investigated a set of sand dunes which accumulated alongside the city wall of South Heishuiguo ancient city (SHC) from the middle Hexi Corridor in arid northern China. Dating these dune sands can provide the timing of both desertification and city abandonment. A series of sand samples (a total of 20) were collected, and their ages were determined by luminescence dating of K-feldspar fraction. The results suggest an abrupt sand dune accumulation between 0.40 ± 0.03 ka and 0.25 ± 0.02 ka, corresponding to 1590–1790 CE. This study confirms a phase of desertification between the late 16th century and the late 18th century in the Hexi Corridor, and the abandonment of the SHC at the ~17th century. In order to assess the anthropogenic influences on desertification, we also reconstructed the population history of the Hexi Corridor over the last 2000 years based on historical literature as a quantitative index of human activity intensity. By comparison of the timing of onset of desertification around the SHC with robust paleoclimate and historical population reconstructions, we conclude that (1) the desertification of 1590–1790 CE was likely the result of considerably enhanced human activities between the late Ming and the early Qing Dynasties, as this period was dominated by a relatively moist climate and could restrain the sand deflation; and (2) the desertification in turn caused abandonment of SHC as the impact of environmental changes on people.