The volcanic eruption, or series of eruptions that occurred around 1345, may have been the first step in a chain that eventually led to the Black Death, which killed between 80 and 200 million people in Europe and Asia. That’s the main conclusion of a study published Thursday in the journal Earth and Environment CommunicationsWhich addresses the reasons for the start and spread of the plague, which spread throughout Europe between 1347 and 1353 AD. C. The death rate reaches 60% in some areas.
For this work, Martin Bausch of the Leibniz Institute for Eastern European History and Culture (GWZO) and Ulf Buntgen of the University of Cambridge reviewed previously published tree-ring data from eight European regions, estimates of volcanic sulfur levels derived from ice cores collected in Antarctica and Greenland, and written documents from the time.
What connection could a volcanic eruption have with the plague? The combined evidence found by the authors suggests that volcanic activity at an unknown location in the tropics around 1345 caused increased levels of sulfur and ash in the atmosphere, as well as wet, cold conditions across southern Europe and the Mediterranean region.
The researchers were able to estimate this eruption using information contained in tree rings from the Spanish Pyrenees, where unusually cold and wet summers were recorded in 1345, 1346 and 1347 across much of southern Europe. While one cold year is not uncommon, consecutive cold summers are highly unusual. Documentary evidence from the same period indicates unusual clouds and a dark lunar eclipse, which also suggest volcanic activity.
The final link to the epidemic is that this climate cooling due to volcanic activity and the subsequent famine led Italian city-states to import shipments of grain from the Black Sea region that would have contained plague bacteria, Yersinia pestis.
This would not be the first time that volcanic eruptions have had a direct impact on human history. A recent study suggested, for example, that volcanic activity may have contributed to the collapse of many Chinese families. It is known that the volcanic eruption in 1783 at the Icelandic fissure known as Laki covered the skies of Europe with ash and led to crop shortages, which, according to some historians, played a role in the outbreak of the French Revolution.
Need more pills
According to written evidence collected in the study, these conditions simultaneously caused crop failure and famine in large areas of Spain, southern France, northern and central Italy, Egypt, and the Levant. This led to Italian maritime city-states, such as Venice and Genoa, negotiating a ceasefire in an ongoing conflict with the Mongols of the Golden Horde and importing large quantities of grain from the Black Sea region in around 1347 AD. C.
Although written sources from Venice indicate that this grain trade saved its population from starvation, the timing of the arrival of grain ships and outbreaks of plague in grain-importing cities suggest that it may also have brought fleas infected with plague bacteria. These infected fleas may have then been distributed in grain shipments to other parts of Italy, such as Padua, exacerbating the spread of the Black Death throughout Europe.
These powerful Italian city-states created roads that allowed them to prevent famine, but which could lead to a much greater disaster.
Martin Bausch
— Researcher at the Leibniz Institute for Eastern European History and Culture (GWZO) and lead author
“Over the course of more than a century, these powerful Italian city-states established long-distance trade routes across the Mediterranean and the Black Sea, which allowed them to activate a highly efficient famine prevention system,” says Bausch. “But this will ultimately inadvertently lead to a much greater disaster.”
Once plague-infected fleas arrived in Mediterranean ports in the 14th century on grain ships, they became a disease-transmitting vector, allowing the bacteria to jump from mammalian hosts—primarily rodents, but likely including domestic animals—to humans. The disease then spread rapidly throughout Europe, devastating the population.
“We were also able to show that many Italian cities, even large ones like Milan and Rome, may not have been affected by the Black Death, apparently because they did not need to import grain after 1345,” Bauch notes. “The relationship between climate, famine and grains could explain other waves of plague.”
Researchers say that Perfect storm The climatic, agricultural, and socio-economic factors after 1345 that led to the Black Death can also be seen as an early example of the consequences of globalization. “Although the coincidence of factors that contributed to the Black Death appears extraordinary, the likelihood of zoonotic diseases arising from climate change leading to epidemics is likely to increase in a globalized world,” Böntgen concludes. “This is especially important given our recent experiences with COVID-19.”
Change the course of history
Marta Dominguez Delmas, expert in Natural Biodiversity Centre From the Netherlands, highlights that thanks to the information provided by trees, the study links climate phenomena to events that changed the course of human history.
“The reconstruction based on tree rings shows a sudden and radical drop in summer temperatures for three consecutive years, which certainly had devastating effects on crops, and thus on grain supplies in the Mediterranean, as the study indicates,” the specialist says.
This tree-ring-based reconstruction shows a sudden and drastic drop in temperature that certainly had devastating effects on crops.
Marta Dominguez Delmas
— An expert in age-study at the Naturalis Center in the Netherlands
From Dominguez Delmas’ point of view, it makes sense that merchant ships, having to search for new sources of grain supplies, would arrive at ports where rodents carrying plague bacteria also roamed, bringing back not only grain to the Mediterranean, but plague as well.
Laia Andrew-Hailes, an ICREA researcher and paleontology expert, believes the authors made the right choice in selecting tree rings. “Only these units can provide annual temperature accuracy associated with a specific calendar year, although they recognize that humidity data is not precise,” he points out. In his opinion, the work is a good example of how to take climate changes into account when studying historical facts. He emphasizes that this does not mean that volcanoes directly promoted the plague, but rather that they created the conditions that later ended in a series of events.
Geologist and well-known Nahum Méndez Chazara confirms that this connection between volcanic eruptions and social changes was, until a few years ago, very difficult to find, but thanks to new technologies that allow us to analyze and date better, it is possible that in the future we will continue to see studies like this one with which we can explain transformations or changes between historical periods related to the natural functioning of our planet.
For Méndez Chazara, it is becoming increasingly clear that there is an important relationship between important pulses of volcanic activity and the occurrence of social and economic changes and even the transmission of diseases. He asserts that “these changes are sufficient to generate a great deal of social instability in times when there were no ways to preserve something as important as food and human life depended primarily on annual crops for survival.”
“The similarities to the current global landscape are enormous,” Dominguez Delmas concludes. “Climate change, global political and social instability, wars, and the recent pandemic that has claimed millions of lives around the world. The trees that survive us will tell humanity in the future what happened, without bias or filters.”