Study Suggests 1345 Volcanic Eruptions Helped Spark the Black Death

A new interdisciplinary study proposes that one or more volcanic eruptions around 1345 set off a chain of environmental and social events that helped turn a local zoonotic infection into the pandemic known as the Black Death.

What the Researchers Found

Researchers from the University of Cambridge and the Leibniz Institute for the History and Culture of Eastern Europe (GWZO) published their findings in the journal Communications Earth & Environment. Using paleoclimate evidence, historical records of grain movements and epidemiological reasoning, the team argues that volcanic aerosols reduced sunlight for several years. That cooling likely caused widespread crop failures, raising fears of famine across parts of Europe.

To relieve food shortages, maritime city-states such as Venice and Genoa imported large quantities of grain from regions around the Black Sea. The authors suggest that some of these grain cargos were infested with rat fleas carrying the bacterium Yersinia pestis, which causes bubonic plague. Fleas on board could have moved from rats to humans after grain was unloaded and stored in port granaries, enabling rapid local transmission.

“The plague bacterium infects rat fleas, which seek out their preferred hosts—rats and other rodents. Once these hosts have died from the disease, the fleas turn to alternative mammals, including humans,”

said co-author Martin Bauch.

The study highlights that the first recorded human plague cases in Venice appeared less than two months after the arrival of the final grain shipments—a timing the authors say supports their hypothesis. Death rates from the Black Death are estimated to have reached up to 60% in some communities, and the pandemic had profound demographic, economic, political and cultural consequences across Europe.

Broader Implications

The researchers frame the Black Death as “a striking interaction of climate, famine and disease” and as an early consequence of expanding long-distance trade and connectivity. They also warn that the convergence of environmental stresses and globalized trade can increase the risk that zoonotic infections will emerge and spread—an observation with clear relevance for today's warmer, highly connected world.

Study Source: Communications Earth & Environment; authors affiliated with the University of Cambridge and the Leibniz Institute for the History and Culture of Eastern Europe (GWZO).