Did Volcanoes Spark the Black Death?

Explore

HHuman history is riddled with periods of death and destruction on an unimaginable scale. Among these calamitous eras, one stands out: the Black Death. The mid-14th century plague killed tens of millions of people across Europe, Asia, and Africa and changed the course of history, marking the end of the Middle Ages and paving the way for the cultural awakening of the Renaissance by disrupting society, the feudal system, and economies across the continent.

Researchers have long known the main villain of the Black Death: bacteria Yersinia pestiswhich caused the bubonic plague that swept through towns and villages with a mortality rate of up to 60 percent. Experts also know that this microbial agent was spread by fleas, carried on the backs of harmful rodents and perhaps pets, and transmitted between humans through air and bodily fluids. But historians have had a harder time recreating the sequence of events that initially sparked the devastating pandemic.

Now two scientists have discovered new clues hidden in tree rings. By examining these rings in the Spanish Pyrenees, along with details of historical accounts from the time, they suggest that increased volcanic activity around 1345 may have triggered a famine, setting off the sequence of events that ultimately led to the Black Death that raged across Eurasia from 1347 to 1353. They published their findings today in Earth and Environment Communications.

“We studied the period before the Black Death with respect to food security systems and recurring famines, which was important to put the situation after 1345 in context,” Martin Bauch, a historian of medieval climate and epidemiology at the Leibniz Institute for Eastern European History and Culture and co-author, said in a statement. “We wanted to examine climatic, environmental and economic factors together, to better understand what triggered the outbreak of the second plague pandemic in Europe. »

Read more: »The volcano that enveloped the Earth and gave birth to a monster»

Here is the model proposed by Bauch and his colleague Ulf Büntgen, a dendrochronologist at the University of Cambridge. As yet unknown volcanic eruptions released enormous amounts of ash and gas into the atmosphere around 1345, causing a drop in annual temperatures that persisted for several years. Cross sections of living and relict trees that the researchers studied had “blue rings,” denoting unusually cold and wet summer growing seasons, in 1345, 1346, and 1347. Additional accounts from the time considered by Bauch and Büntgen report abnormal cloudiness and dark lunar eclipses, other clues to volcanic activity. This prolonged cooling could have caused widespread harvest failures throughout the Mediterranean.

The resulting food shortages caused merchants in the maritime republics of Venice, Genoa, and Pisa to increase their grain imports from the Mongols living around the Sea of ​​Azov in 1347. Along with grain shipments using established trade routes came plague-infested fleas. Once Y. pestis and the fleas that carried it landed in Europe, the pathogen spread to rats, mice and perhaps pets. Eventually, the disease spread to humans, and people began transmitting it in densely populated centers. The rest is a dark part of the story.

“For over a century, these powerful Italian city-states had established long-distance trade routes across the Mediterranean and Black Seas, allowing them to activate a very effective system for preventing famine,” Bauch said. “But ultimately it would inadvertently lead to a much bigger catastrophe.”

From this newly proposed picture of the roots of the Black Death, Bauch and Büntgen suggest a lesson for humans today. “Although this unique spatio-temporal coincidence of many influences appears rare, our results highlight the increased likelihood of zoonotic infectious diseases suddenly emerging and quickly translating into pandemics in a globalized, warmer world, with COVID-19 being only the latest warning sign,” they write.

Continuing to study the intricacies of history’s most devastating episodes could help us avoid repeating the mistakes made in the wake of natural disasters.

Enjoy Nautilus? Subscribe for free to our newsletter.

Main image: Fresco, known as the “Triumph of Death”, attributed to Buonamico Buffalmacco; photo by Martin Bauch

• Bob Grant

  Published on December 4, 2025

  Bob Grant is the associate editor of Nautilus.