The devastating pandemic known as the Black Death, which claimed an estimated 25 million lives across Europe between 1347 and 1351, may have been triggered by a volcanic eruption, according to groundbreaking research. A team of scientists and historians propose that an eruption around 1345 created a climatic disturbance that set off a chain of events leading to one of history’s worst pandemics. Their findings were published in the journal Communications Earth & Environment.
The researchers utilized tree ring data from various regions in Europe, alongside ice core samples from Antarctica and Greenland, to reconstruct the climate of the 14th century. They identified a series of environmental changes that likely contributed to crop failures and subsequent food shortages. This climatic downturn coincided with a significant drop in temperatures, which would have severely impacted agricultural output throughout the Mediterranean region.
According to study coauthor Martin Bauch, a historian at the Leibniz Institute for the History and Culture of Eastern Europe in Germany, the research indicates that the haze produced by volcanic ash could have blocked sunlight for several years. This would have contributed to a famine in Italian city-states, including Venice and Genoa, leading to emergency imports of grain from the Black Sea region to stave off starvation.
The grain shipments, however, were infested with Yersinia pestis, the bacterium responsible for the plague. Bauch explained that rat fleas, which thrive in grain stores, can survive on grain dust for extended periods. Once the grain reached port cities, the bacteria would have had the opportunity to spread rapidly among the population.
Bauch noted, “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.”
The population of the world before the Black Death was approximately 450 million. The catastrophic loss of life during the pandemic had profound societal and economic consequences that reverberated across Europe for decades.
The Environmental Connection
While the role of maritime trade in spreading the plague had been previously recognized, this study is pioneering in attributing the initial cause of the pandemic to a volcanic eruption. Bauch highlighted that the most severe famines in the 13th and 14th centuries occurred in the years directly preceding the Black Death.
To solidify their hypothesis, Bauch collaborated with Ulf Büntgen, a professor of environmental systems analysis at the University of Cambridge. They aimed to find scientific evidence to complement Bauch’s historical research. Büntgen elaborated on their approach, stating, “We are talking about something that happened 800 years ago. Where do we get information about climate? We have a limited number of sources.”
Büntgen examined thousands of tree samples from living and ancient trees across Europe to analyze growth patterns, which provide insights into historical climate conditions. He observed that the tree rings indicated a period of cooling that aligned with Bauch’s findings regarding famine.
The study also analyzed ice core data for sulfur spikes, which would further support the occurrence of a significant volcanic eruption. Büntgen noted, “Large, sulfur-rich volcanic eruptions are known to produce a cooling in the following summers.”
This volcanic link could help explain why the Black Death had a disproportionately severe impact in certain areas of Europe, with some regions losing up to 60% of their population, while others remained largely unaffected. For instance, cities like Rome and Milan managed to avoid the worst of the pandemic due to their proximity to grain-producing areas, reducing their reliance on imports.
Implications for Understanding Pandemics
The research not only sheds light on the links between climate events and disease outbreaks but also highlights the interconnectedness of various factors leading to the Black Death. The findings suggest that a combination of natural, social, and economic forces must converge for a pandemic of such magnitude to occur.
Mark Welford, a professor and head of geography at the University of Northern Iowa, emphasized the study’s contribution to understanding how climate change and disease dynamics intersect. He remarked, “The authors recognize that an event as exceptional as the Black Death must have been due to an exceptional coincidence of natural and social forces.”
Mark Bailey, a professor of late medieval history at the University of East Anglia, pointed out that the study advances the ongoing debate about how fluctuations in weather patterns might have influenced the onset of the Black Death. He acknowledged the novelty of linking volcanic activity and changes in grain trade routes to the pandemic’s timing.
The research underscores the importance of understanding historical pandemics to inform future preparedness. Alex Brown, an associate professor at Durham University, praised the study for demonstrating the critical relationships between people, animals, and the environment. He stated, “Bauch and Büntgen’s study highlights the significance of understanding the interconnectedness of various systems, which is essential for both historical studies and future pandemic responses.”
This latest research adds a compelling dimension to the understanding of the Black Death, illustrating how a natural disaster can have far-reaching consequences on human health and society.
