Climate change and epidemics in Chinese history: A multi-scalar analysis

Did Hydro-climatic Extremes, Positive Checks, and Economic Fluctuations Modulate the Epidemics Outbreaks in Late Imperial China?

Empirical research has shown that climate-related variables, the decline in economic well-being, and the mutual reinforcement of positive checks are the primary drivers of epidemic outbreaks in recent human history. However, their relative importance in causing the outbreak of epidemics is rarely examined quantitatively in a single study. I sought to address this issue by analyzing the 1402 epidemic incidents in China between 1841 and 1911, which partially overlaps partly with the Third Pandemic period. Fine-grained historical big data, multiple regression, and wavelet coherence analysis were employed. Statistical results show that economic fluctuations drove the country-wide epidemics outbreaks in China in inter-annual and decadal time scales. Economic fluctuations could cause short-term hardship and long-term impoverishment to the underprivileged social groups since a large portion of the Chinese population lived at the subsistence level in the past. The fluctuations might have sustained the repeated waves of epidemic outbreaks during the Third Pandemic period.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10745-021-00272-7.

Drought-induced spatio-temporal synchrony of plague outbreak in Europe

Plague synchronously swept across separated regions in Europe throughout history. However, the spatio-temporal synchrony of plague and its driving mechanism have not been thoroughly investigated. In this study, we transformed the historical European plague database spanned 1347-1800 CE into country-level time-series that differentiated large-scale plague outbreak from counted data. We found that there are 74 years in which two or more countries in our study region (UK, France, Germany, Spain, and Italy) experienced large-scale plague outbreak in the same year. Our Multivariate Ripley's K-function results showed that the onset year and the cessation year of large-scale plague outbreak are synchronized at the 0-23-year and 0-20-year windows, respectively. The temporal association between such synchrony and climatic forcing was further investigated using the Superposed Epoch Analysis, and drought was found to be responsible for the synchrony. Integrating our results with a literature survey, we suggested that prior to the peak of plague, the occurrence of drought and the subsequent reintroduced rainfall dampened both the rodent community and human society and boosted the number of fleas that carried plague. Such a synthesis facilitated the outbreak of plague. At the same time, high temperature associated with such drought also confined the geographic diffusion of the plague. Hence, although continental mega-drought could initiate the synchrony of plague outbreak, the synchrony actually consisted of a number of localized plague outbreak events scattering across different regions in Europe. According to the projected rising trend of drought in terms of its magnitude, duration, and geographic extent, the risk of synchrony of rodent-borne diseases in Europe will be significantly elevated, especially in France, Italy, and Spain.

Climate and society in long-term perspective: Opportunities and pitfalls in the use of historical datasets

Recent advances in paleoclimatology and the growing digital availability of large historical datasets on human activity have created new opportunities to investigate long-term interactions between climate and society. However, noncritical use of historical datasets can create pitfalls, resulting in misleading findings that may become entrenched as accepted knowledge. We demonstrate pitfalls in the content, use and interpretation of historical datasets in research into climate and society interaction through a systematic review of recent studies on the link between climate and (a) conflict incidence, (b) plague outbreaks and (c) agricultural productivity changes. We propose three sets of interventions to overcome these pitfalls, which involve a more critical and multidisciplinary collection and construction of historical datasets, increased specificity and transparency about uncertainty or biases, and replacing inductive with deductive approaches to causality. This will improve the validity and robustness of interpretations on the long-term relationship between climate and society. This article is categorized under: Climate, History, Society, Culture > Disciplinary Perspectives.

Pre-industrial plague transmission is mediated by the synergistic effect of temperature and aridity index

Background

Although the linkage between climate change and plague transmission has been proposed in previous studies, the dominant approach has been to address the linkage with traditional statistical methods, while the possible non-linearity, non-stationarity and low frequency domain of the linkage has not been fully considered. We seek to address the above issue by investigating plague transmission in pre-industrial Europe (AD1347–1760) at both continental and country levels.

Methods

We apply Granger Causality Analysis to identify the casual relationship between climatic variables and plague outbreaks. We then apply Wavelet Analysis to explore the non-linear and non-stationary association between climate change and plague outbreaks.

Results

Our results show that 5-year lagged temperature and aridity index are the significant determinants of plague outbreaks in pre-industrial Europe. At the multi-decadal time scale, there are more frequent plague outbreaks in a cold and arid climate. The synergy of temperature and aridity index, rather than their individual effect, is more imperative in driving plague outbreaks, which is valid at both the continental and country levels.

Conclusions

Plague outbreaks come after cold and dry spells. The multi-decadal climate variability is imperative in driving the cycles of plague outbreaks in pre-industrial Europe. The lagged and multi-decadal effect of climate change on plague outbreaks may be attributable to the complexity of ecological, social, or climate systems, through which climate exerts its influence on plague dynamics. These findings may contribute to improve our understanding of the epidemiology of plague and other rodent-borne or flea-borne infectious diseases in human history.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3045-5) contains supplementary material, which is available to authorized users.