There are few episodes in the history of humanity more famous, studied and debated than that of the Black Deaththe epidemic that spread death across Europe between 1347 and 1353. However, there remained an enigma to solve, one as basic as it was relevant: Why the hell did the epidemic break out when, where and how did it do so? Why did this wave of death break out in the 14th century and not before or after?
Solving a puzzle. This mystery is what Martin Bauch and Ulf Büntgen, from the GWZO and the University of Cambridge respectively, have wanted to solve in a study just published in Communications Earth & Environment.
With it they not only want to shed light on one of the darkest episodes in Europe. They also show that, almost seven centuries later, the “black death” continues to be one of the chapters that most fascinates the world. Nothing surprising if one bears in mind that between 1347 and 1353 it took millions of lives in Europe, reaching mortality rates that in some regions they touched 60%.
Searching in the Pyrenees. Perhaps the most curious thing about Bauch and Büntgen’s study is that it does not start in historical archives. Or that wasn’t at least his main place of work. The key to his research is in the Spanish Pyrenees, more specifically in the secular pines that they found there.
When studying the interior of their trunks in search of clues about the medieval climate of Europe, they found something unexpected: a succession of “blue rings”. For most, that detail would go unnoticed, but Bauch and Büntgen saw something in it: evidence of a chain of colder, wetter summers than usual.
“Unusual summers”. When the tempera falls, the trees cannot properly lignify their cells, which in turn leaves a bluish mark in the ring register of the trunk. In the Pyrenean pines, researchers found such marks that suggest that much of southern Europe must have experienced “unusually cold and wet summers” in 1345, 1346 and 1347.
What’s more, when digging through libraries and written sources they found clues that point in exactly the same direction: a period marked by “unusual cloudiness and dark lunar eclipses.” The next question is… What caused this change in climate? And why is it important?
The power of an eruption. Regarding the first question, researchers have few doubts. In his opinion, the drop in temperatures in summer was caused by a volcanic eruption (or even a chain of them) recorded around the year 1345 and which triggered a fatal domino effect: a considerable expulsion of ash and volcanic gases that generated a layer and caused a drop in temperatures, just as happened in other episodes throughout history.
Climate, agriculture… Hunger. For the next question, why is it important that a volcano began releasing gases and ash almost seven centuries ago, the answer is simple: agriculture. The changes in climate not only left their mark on the centuries-old trunks of the central Pyrenees, they also punished the fields of the Mediterranean region, reducing crops and generating losses that threatened to lead to famine… and social instability.
Against this backdrop, the powerful maritime republics of Italy did the most logical thing: chartered ships to import grain from the east, from the Black Sea area, more specifically from the Golden Hordein the Sea of Azov region.
It didn’t matter that Genoa and Venice were at war with the Mongols. Hunger was pressing, the threat of riots loomed and European diplomacy did its job. Already late in 1347, ships with grain began to arrive in Europe, unloading their precious merchandise in Mediterranean ports.
More than grain. The problem is that in the holds of the ships mobilized by Venice and Genoa, the same ones that were supposed to prevent Europe from being besieged by famine, there were not only tons of grain. On board they brought fleas infected with Yersinia pestisthe bacillus responsible for the bubonic plague.
“The exact origin of this deadly bacteria is still unknown, but ancient DNA suggests that a natural reservoir may have existed in wild gerbils somewhere in central Asia,” they explain from the University of Cambridge. The result: grain ships suddenly became vectors of a fatal disease, the bacteria jumped from rodents to humans, and the Black Death soon spread across Europe, with something much worse than famine.
The ships of the black death. The rest is known history. Between 1347 and 1353 the disease killed millions of people. It is often said that the plague took the lives of 60% of the European population, a percentage that some raise to 65%, although in recent years some studies They have warned that the calculation is overstated and there were regions in which the registry was maintained.
“Evidence of the Black Death can be found in many European cities almost 800 years later,” Büntgen and Bauch explain. “We were also able to show that many Italian cities, such as Milan or Rome, were probably not affected, because they did not need to import grain after 1345.”
Why is it important? The study is interesting for several reasons. The main one, because it sheds new light on an aspect as basic as until now enigmatic about the Black Death. We knew about the role of Yersinia pestisabout the ships, about the role played by rodents, we knew the tragic death toll, its impact on the society, culture and economy of Europe… But we did not know why the epidemic broke out just when it did and not before or after.
The succession of factors is so fascinating that researchers speak of a “perfect storm” in which climatic, agricultural, social and economic factors were added. A cocktail that, they insist, does not only speak to us about the Middle Ages.
“Although this coincidence seems unusual, the probability of zoonotic diseases emerging due to climate change and resulting in pandemics is likely to grow in a globalized world,” Buntgen adds.. “It is especially relevant given our recent experiences with the COVID pandemic.”
Images | Wikipedia and University of Cambridge
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