# Study on the differentiated impact of climate change on plague epidemics in Northern and Southern China, 1912–1949

## TL;DR

This study examines how climate change affected plague outbreaks differently in northern and southern China from 1912 to 1949.

## Contribution

The study reveals distinct spatiotemporal patterns and climate drivers of plague epidemics in northern and southern China.

## Key findings

- Southern plague shows a high-amplitude stable decline trend, while northern plague has a slow decline amid fluctuations.
- Northern plague is influenced by precipitation and temperature interactions, while southern plague is sensitive to warming transitions.
- Climate abrupt changes act as triggers for epidemic shifts, with northern peaks delayed after precipitation changes.

## Abstract

Based on plague disaster and climate data from China between 1912 and 1949, this study comprehensively employed the Mann-Whitney U test, mutation test, and optimal parameter geographic detector to investigate the relationship between plague epidemic characteristics and climate change across different geographic regions. Findings reveal significant spatiotemporal divergence in plague epidemics between northern and southern China: Southern plague exhibits a clearly defined “high-amplitude stable decline” trend, while northern plague shows a slow downward trajectory amid intense fluctuations, lacking a significant linear trend. Moreover, all three plague hotspots highly overlap with natural reservoirs. This divergence stems from fundamentally different climate-driven mechanisms in the north and south, with interactive detection indicating that synergistic effects between dual factors generally outweigh single-factor impacts. Northern plague is jointly controlled by precipitation fluctuations and thermal variations, primarily driven by the interaction between annual precipitation and trends in annual mean high temperatures (q-value: 31.46%); In contrast, southern plague is more sensitive to warming transitions in the climate system, primarily governed by the synergistic effects of annual temperature difference variations and trends in low temperatures, precipitation, and mean temperature (q-values: 38.44%, 34.92%, and 34.77%). Spatio-temporal coupling analysis further reveals that climate abruptions act as temporal triggers for epidemic shifts: Northern plague exhibits delayed peaks 1–2 years after precipitation abruptions, while Southern plague frequency declines during high-temperature abruptions. Spatially, high-value zones of Northern annual high-temperature trends form ecological barriers segmenting adjacent hotspots, whereas Southern low-value zones of annual temperature difference trends correspond to plague hotspots. By elucidating historical variations in plague sensitivity to climate fluctuations, this study provides crucial historical evidence and reference for contemporary plague surveillance and public health risk assessment under climate change.

The period from 1912 to 1949 coincided with the third major plague pandemic. Compared to the stringent control measures implemented by the Chinese government after the nation’s founding in 1949, the plague epidemics during this era more accurately reflected the natural characteristics of the disease. This provides a unique window for studying the inherent relationship between epidemics and climate. Through coupled analysis of plague epidemics and climate variations from 1912 to 1949, this study reveals distinct spatiotemporal patterns in plague distribution between northern and southern China. These differences stem from varying climatic drivers and ecological contexts. Abrupt climate shifts act as ‘triggers’ that periodically alter the spatial distribution of plague epidemics, while long-term climate trends shape the geographical boundaries of plague prevalence. This research deepens our understanding of the natural plague-climate relationship, providing scientific basis for assessing plague risks under current and future climate conditions and formulating control strategies.