The 1855 to 1859 locust plague in China

Historical disaster studies tend to be addressed from various perspectives, and case studies (i.e., event reconstruction) are an important aspect of such research. Using records extracted from historical documents and focusing on locust plague events, this study investigated disasters that occurred from 1855 to 1859. The objective was to reconstruct the temporal dynamics and spatial patterns of a major locust plague event to explore the social impact and reveal the underlying climate trends. The results suggested that: (1) the locust plagues followed an approximately 5-year duration from 1855 to 1859. Over this period, the frequency of individual plagues varied greatly and 1857 was the peak year. Locust plagues showed clear distribution patterns on a spatial scale during this period, with the mean center located in Henan Province. Locust plagues tended to be localized at the beginning and then spread out from the original locations, presenting a general spatial pattern of “radiating after clustering.” (2) Locust plagues were closely related to drought and showed a correlation with the overall drainage pattern of major bodies of water in the regions studied. The main reason for the locust plagues was probably drought events, climate and other geographic factors. The droughts were likely related to teleconnection between the increasing El Niño, frequency of sunspot activity and declining SSTs. (3) Locust plagues impacted society and damaged agricultural yields, as indicated by higher rice prices and increased wars. A hysteresis transfer effect was observed between locust plagues and the corresponding social responses; rice prices increased about half to 1 year after locust plagues occurred, while the frequency of wars increased after a clear delay of about 1–2 years. This showed locust plagues caused the rice price and refugee increasing and then caused social unrest.