For more than a century, these powerful Italian city-states had established long-distance trade routes across the Mediterranean and the Black Sea, allowing them to activate a highly efficient system to prevent starvation. But ultimately, these would inadvertently lead to a far bigger catastrophe
Martin Bauch
This climate-driven change in long-distance trade routes helped avoid famine, but in addition to life-saving food, the ships were carrying Yersinia pestis, the deadly bacterium that ultimately caused the Black Death, enabling the first and deadliest wave of the second plague pandemic to gain a foothold in Europe. This is the first time that it has been possible to obtain high-quality natural and historical proxy data to draw a direct line between climate, agriculture, trade and the origins of the Black Death.
The Black Death was one of the largest disasters in human history. Between 1347 and 1353, it killed millions of people across Europe. In some parts of the continent, the mortality rate was close to 60%.
While it is accepted that the disease was caused by Yersinia pestis, which originated from wild rodent populations in central Asia and reached Europe via the Black Sea region, it’s still unclear why the Black Death started precisely when it did, where it did, why it was so deadly, and how it spread so quickly. “This is something I’ve wanted to understand for a long time,” said Professor Ulf Büntgen from Cambridge’s Department of Geography. “What were the drivers of the onset and transmission of the Black Death, and how unusual were they? Why did it happen at this exact time and place in European history? It’s such an interesting question, but it’s one no one can answer alone.”
Büntgen, whose research group uses information stored in tree rings to reconstruct past climate variability, worked with Dr Martin Bauch, a historian of medieval climate and epidemiology from the Leibniz Institute for the History and Culture of Eastern Europe, on the study. “We looked into the period before the Black Death with regard to food security systems and recurring famines, which was important to put the situation after 1345 in context,” said Bauch. “We wanted to look at the climate, environmental and economic factors together, so we could more fully understand what triggered the onset of the second plague pandemic in Europe.”
Together, they combined high-resolution climate data and written documentary evidence with conceptual reinterpretations of the connections between humans and climate to show that a volcanic eruption – or series of eruptions – around 1345 was likely the first step in a sequence that ultimately led to the Black Death.
The researchers were able to approximate this eruption through information contained in tree rings from the Spanish Pyrenees, where consecutive ‘Blue Rings’ point to unusually cold and wet summers in 1345, 1346 and 1347 across much of southern Europe. While a single cold year is not uncommon, consecutive cold summers are highly unusual. Documentary evidence from the same period notes unusual cloudiness and dark lunar eclipses, which also suggest volcanic activity. This volcanically forced climatic downturn led to poor harvests, crop failure and famine. However, the Italian maritime republics of Venice, Genoa and Pisa were able to import grain from the Mongols of the Golden Horde around the Sea of Azov in 1347. “For more than a century, these powerful Italian city-states had established long-distance trade routes across the Mediterranean and the Black Sea, allowing them to activate a highly efficient system to prevent starvation,” said Bauch. “But ultimately, these would inadvertently lead to a far bigger catastrophe.”