The effect of environmental changes on locust outbreak dynamics in the downstream area of the Yellow River during the Ming and Qing Dynasties.

Locust outbreaks were one of the primary biological disasters in ancient China. Using historical data from the Ming and Qing Dynasties, the temporal and spatial relationships between the changes in the aquatic environment and the locust dynamics in the downstream areas of the Yellow River were investigated via quantitative statistics, and other factors affecting locust outbreaks were also studied. This study demonstrated that locust, drought and flood outbreaks were spatiotemporally correlated. Locusts and droughts were synchronous for long-term series, but locust outbreaks were weakly correlated with floods. In drought years, the probability of a locust outbreak occurring in the same month as a drought was higher than that in other years and months. The probability of a locust outbreak was higher in the one to two years following a flood than in other years, but locusts were not easily triggered by extreme flooding. In the waterlogged and riverine locust breeding areas, locust outbreaks were more closely related to flooding and drought than in other breeding areas. Affected by the diversion of the Yellow River, the areas of frequent locust outbreaks were around riverine areas. In addition, climate change affects the hydrothermal conditions in which locusts occur, and human activities influence the occurrence of locusts by changing their habitats. Analyzing the relationship between historical locust outbreaks and water system changes provides valuable information for formulating and implementing disaster prevention and mitigation policies in this region.