Demographic impact of climate change on northwestern China in the late imperial era

A growing body of quantitative (large-N) studies examines the climate–man nexus in historical agrarian China. Their dominant approach is to take the whole of China as a spatial aggregate, without taking into account the role of regional context. Furthermore, quantitative investigations of the climate–man nexus in northwestern (NW) China remain scarce. This study seeks to address the above issues. We focused on the extent to which periodic fluctuation of precipitation and temperature affected positive checks (famine, epidemics, nomadic invasion, and rebellion) and subsequently population growth dynamics in Sha'anxi, Gansu, and Ningxia, NW China in AD 1500–1911. Multiple Wavelet Coherence and Partial Wavelet Coherence analyses were applied to handle the non-linear and non-stationary nature of the climate–man nexus. Our results show that drought was the common stressor of various positive checks in NW China at the multi-decadal (32–64 year) time-scale. In addition, there was a coherence break of the relationship in AD 1700–1820, owing to the tremendous increase of subsistence brought about by land reclamation policy and the introduction of foreign food crops. Yet, the coherence resumed afterwards, resulting in more disastrous demographic consequences. We highlighted that the climate–man nexus is not entirely deterministic in nature, even in environmentally-fragile NW China. The relationship is mediated by social factors, particularly government policies. Still, if those measures are made at the expense of the environment, although humans might be able to win over nature in the short-term, the final outcome could be catastrophic in the long-term. This study substantiates the above notion with empirical quantitative evidence. Copyright © 2016 Elsevier Ltd.