Prolonged drought and associated social unrest on the Tibetan Plateau played a role in the emergence and spread of the Third Plague Pandemic

The Third Plague Pandemic claimed over 15 million lives, making it one of history’s deadliest. However, the complex interplay of environmental and societal factors that triggered the spillover of Yersinia pestis from its natural reservoirs on the Tibetan Plateau into human populations in the 1850s remains unclear. Here, we use 35 moisture-sensitive tree-ring chronologies from the southeastern Tibetan Plateau to reconstruct interannual to multi-decadal hydroclimate variability back to 1564 CE. Our record reveals a prolonged drought from the 1850s to the 1880s, coinciding with the onset and establishment of the Third Plague Pandemic. The reconstructed hydroclimate anomaly was accompanied by sharp increases in famine, conflict and plague that claimed 2.41 million lives during the Panthay Rebellion. Troops, refugees, and opium traders accelerated the spread of the pandemic to and from Hong Kong. Our findings underline the need for plague prevention based on climate-related conflict in a warming, globalized world. A drought from the 1850s–1880s fueled famine, conflict, and the Third Plague Pandemic, killing over 2.4 million in the Panthay Rebellion as troop movements, refugees, and opium trade sped its spread through Hong Kong, according to tree-ring and historical data.