It sounds like the stuff of conspiracy theories or a disaster movie: a series of volcanic eruptions kicks off a deadly pandemic. But new research suggests that such an event may indeed have happened. And the pandemic in question? The most destructive of them all: the Black Death.
Researchers from Cambridge and Leipzig have combined documentary evidence with climate data contained in tree rings to show that Europe suffered a 'perfect storm' of factors that not only sounded the death knell for tens of millions of people, but also led to "profound demographic, economic, political, cultural and religious change." Their results have just been reported in the journal Communications Earth & Environment.
The academics examined ‘blue rings’ in trees from the Spanish Pyrenees. These indicate that the area suffered from abnormally cold and wet summers from 1345 to 1347, potentially caused by ash and gases thrown up by volcanoes. Documents from the era describe the weather as being unusually cloudy and that lunar eclipses were darker than normal, both of which also point to volcanic activity.
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The sudden change in climate resulted in poor harvests across the Mediterranean region, triggering a widespread famine. In 1347, in a bid to stave off looming food riots, the Italian republics of Venice, Genoa and Pisa ordered grain from the Mongols of the Golden Horde who lived around the Sea of Azov (today bordered by Ukraine and Russia).
Unfortunately, the ships that brought the life-saving food also carried rats. And on those rats were fleas harbouring the Yersinia pestis bacterium which was to cause the Black Death.
The research may at last have answered several questions about the disease and how it spread so quickly.
"This is something I’ve wanted to understand for a long time," says 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?"
Fellow researcher Dr Martin Bauch, a historian from the Leibniz Institute for the History and Culture of Eastern Europe in Leipzig, adds, "We wanted to look at the climate, and environmental and economic factors together, so we could more fully understand what triggered the second plague pandemic in Europe."
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Despite being an island nation, Britain was not to be spared. In June 1348, a sailor on a boat from Gascony arrived in Dorset and became the first known victim in England. Estimates vary as to the numbers killed in Britain by the Black Death but the disease seems likely to have wiped out between a third and a half of the population, and possibly more.
This latest research could also influence how future pandemics are addressed. The team suggests that "modern risk assessments should incorporate knowledge from historical examples of the interactions between climate, disease and society."
Given the devastation caused by the most recent pandemic, any lessons that can be learnt from history would surely be welcome.
Top image: Taking tree ring samples from the Pyrenees. Credit: Ulf Büntgen
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