Could Volcanic Eruptions Have Triggered the Black Death?

Throughout history, humanity has faced catastrophic events on unimaginable scales. One of the most infamous of these was the Black Death. Sweeping through Europe, Asia, and Africa in the mid-14th century, this pandemic claimed tens of millions of lives and altered the trajectory of society, ending the Middle Ages and paving the way for the Renaissance by disrupting economies, social systems, and feudal structures.

Scientists have long identified the culprit behind the plague: the bacterium Yersinia pestis, which caused the bubonic plague. This disease spread through fleas carried by rodents, potentially domestic animals, and could pass between humans through airborne particles and bodily fluids. However, historians have struggled to determine the precise chain of events that initiated the pandemic.

Recent research offers new insights through the study of tree rings. Examining growth rings in the Spanish Pyrenees alongside historical records, researchers suggest that increased volcanic activity around 1345 may have triggered a famine, setting off a cascade of events that led to the Black Death sweeping across Eurasia between 1347 and 1353. These findings were published in Communications Earth & Environment.

We investigated the period preceding the Black Death in terms of food security and recurrent famines to better understand the conditions after 1345, explained Martin Bauch, a historian specializing in medieval climate and epidemiology. By analyzing climate, environmental, and economic factors together, we aimed to identify the triggers behind the second plague pandemic in Europe.

The model proposed by Bauch and Ulf Bntgen, a dendrochronologist from Cambridge, suggests that previously unknown volcanic eruptions released vast amounts of ash and gases into the atmosphere around 1345. This caused multi-year drops in temperature. Tree ring cross-sections revealed blue rings, indicative of unusually cold and wet summers in 1345, 1346, and 1347. Contemporary reports also describe abnormal cloud cover and dark lunar eclipses, supporting the theory of volcanic activity.

The resulting cooler climate may have led to widespread crop failures across the Mediterranean. Food shortages pushed merchants in Venice, Genoa, and Pisa to import grain from regions near the Sea of Azov in 1347. Alongside these shipments came plague-infested fleas. Once in Europe, Y. pestis spread to rats, mice, and possibly domesticated animals, eventually reaching humans in densely populated cities, igniting the deadly pandemic.

For over a century, these Italian city-states had developed extensive trade networks to prevent famine, Bauch noted. Yet, these systems inadvertently facilitated a far larger disaster.

From this reconstruction, Bauch and Bntgen draw a contemporary lesson. They caution that while such a convergence of events is rare, it highlights how zoonotic diseases can quickly escalate into pandemics in a globalized and warming world, with COVID-19 serving as a recent warning. Studying the mechanisms behind historys most devastating outbreaks could help modern society avoid repeating similar mistakes.

Author: Aiden Foster