Rare set of varied factors triggered Black Death

Tree ring data allowed Büntgen et al. to determine that there had been a volcanic eruption (or group of eruptions) around 1345, specifically so-called “blue rings” which indicate unusually cold or wet summers, in this case, for three consecutive years (1345, 1346 and 1347). Textual sources also referred to details such as an unusually high degree of cloudiness and dark lunar eclipses, indications of the aftereffects of volcanic activity.

This colder climate in turn led to widespread crop failures and resulting famine, particularly in parts of Spain, southern France, Egypt, and northern and central Italy. While Milan and Rome were largely self-sufficient, the authors argue, smaller urban centers like Bologna, Florence, Genoa, Siena, and Venice relied on a complex grain supply system to import grain from the Mongols of the Golden Horde via trade routes established along the Black Sea coast. Textual evidence supports this, showing substantial increases in grain prices and the imposition of regulations on the grain trade in 1346. This saved people from starvation but also brought Y. pestis along for the ride, with devastating consequences.

According to the authors, although the factors that triggered the spread of the Black Death in Europe are unique, the study illustrates the risks of a globalized world and calls for a similar interdisciplinary approach to future threats. “Although the coincidence of factors contributing to the Black Death appears rare, the likelihood of zoonotic diseases emerging under climate change and translating into pandemics is likely to increase in a globalized world,” Büntgen said. “This is particularly relevant given our recent experiences with COVID-19. »

Earth and Environment Communications, 2025. DOI: 10.1038/s43247-025-02964-0 (About DOI).