Scientists believe they have solved one of history's greatest mysteries: what triggered the devastating Black Death plague that swept through medieval Europe. New research points to a colossal volcanic eruption as the catalyst for the pandemic that wiped out between a third and half of the continent's population in the mid-14th century.
The Climate Clue Hidden in Ice and Trees
A team of researchers from Cambridge and Germany pieced together an extraordinary sequence of events by analysing environmental records and historical texts. Their investigation found evidence of at least one massive tropical volcanic eruption around the year 1345.
Sooty particles trapped deep within the ice sheets of Antarctica and Greenland revealed the eruption shrouded the planet in a thick haze of ash and sulphur. This aligns with contemporary written accounts describing unusually cloudy skies and dark lunar eclipses.
Further proof came from tree rings. Analysis shows a three-year period of stunted tree growth immediately following the suspected eruption, indicating the volcanic haze caused significant climate disruption. This led to cooler, wetter conditions and widespread crop failures.
From Famine to Pandemic: A Deadly Chain Reaction
Dr Martin Bauch, a study author and historian of medieval climate at the Leibniz Institute, explained to Sky News that the eruption's impact on agriculture was the critical first domino to fall. "In the years before the Black Death arrives, there is very unusual weather from England, across the Mediterranean to the Levant," he said.
The resulting famine forced powerful Italian maritime states like Venice, Genoa, and Pisa to seek new food sources. In 1347, they turned to the Mongol Golden Horde around the Black Sea, importing grain to stave off starvation.
This fateful decision for trade had catastrophic unintended consequences. Previous research confirms that ships carrying grain also brought fleas infected with the Yersinia pestis bacterium, likely from wild gerbils in central Asia. Once in European ports, the fleas spread to rats and other mammals, unleashing the plague across the continent.
A Historical Warning for a Globalised World
The study, published in Communications Earth & Environment, frames the Black Death as an early example of a globalised catastrophe. A perfect storm of climatic, agricultural, societal, and economic factors converged to enable the pandemic's spread.
Professor Ulf Buentgen from Cambridge University's Department of Geography, another author, highlighted the modern relevance. "Although the coincidence of factors that contributed to the Black Death seem rare, the probability of zoonotic diseases emerging under climate change and translating into pandemics is likely to increase in a globalised world," he stated.
He drew a direct parallel to contemporary experiences, noting the research is "especially relevant given our recent experiences with Covid-19." The findings serve as a stark reminder of how interconnected climate, ecology, and human society are in shaping our vulnerability to disease.
