In the mid-14th century, a bacteria transmitted by fleas and rats spread rapidly across Asia and Europe, causing deadly cases of bubonic plague. The so-called Black Death was one of the most notorious pandemics in historical memory. Many experts estimate that it killed around 50 million Europeans, most of the continent’s population.
“Widely distributed and numerous data indicate that the Black Death probably wiped out around 60% of the European population,” wrote Norwegian historian Ole Benedictow, one of the leading experts on the Black Death, in 2005. In 2021, when he published “The Complete History of the Black Death”, he raised that estimate to 65%.
But these figures, based on historical documents of the time, greatly overestimate the real number of plague victims, according to a study published on the 10th. By analyzing ancient pollen deposits as markers of agricultural activity, German researchers found that the black plague caused a patchwork of destruction. Some regions of Europe did indeed suffer devastating die-offs, but other regions held steady and still others prospered.
“We can’t go on saying that the plague killed half of Europe,” said Adam Izdebski, an environmental historian at the Max Planck Institute for the Science of Human History in Jena, Germany, and author of the new study.
In the 14th century most Europeans worked in agriculture, which involved intensive manual labor to produce crops. If half of all Europeans had died between 1347 and 1352, agricultural activity would have been drastically reduced.
“Half the workforce would have disappeared overnight,” Izdebski said. “It would not be possible to maintain the same level of land use. It would be impossible to continue cultivating many fields.”
The loss of half the population would have converted many farms into uncultivated fields. Without enough herders to tend the cattle, the pastures would have been overgrown with weeds. Shrubs and trees would have taken over these areas and, over time, would have given way to mature forests.
Izdebski and his colleagues calculated that if the Black Death had indeed brought about such a transformation, they should be able to detect them in the pollen species that survived from the Middle Ages. Every year, plants release huge amounts of pollen into the air, and some of that pollen ends up at the bottom of lakes and swamps. Buried in the sludge, the grains can survive for centuries.
To find out what pollen had to say about the Black Death, Izdebski and his colleagues selected 261 sites across Europe — from Ireland and Spain in the west to Greece and Lithuania in the east — that contained preserved grains dating to approximately between 1250 and 1450.
In some regions, such as Greece and central Italy, pollen told a story of devastation. Pollen from species such as wheat had been greatly reduced. Dandelions and other flowers from pasture areas were gone. Fast-growing trees such as beeches appeared, followed by slowly growing trees such as oaks.
But the same thing did not happen across Europe. In fact, only 7 of the 21 regions studied by the researchers underwent catastrophic changes. Elsewhere the pollen registered little or no change.
In fact, the landscape has shifted in the opposite direction in regions such as Ireland, central Spain and Lithuania. Pollen from mature forests became rare, while pollen from agricultural and pasture areas became even more common. In some cases, two contiguous regions followed different paths, with pollen suggesting that one had become forest while the other had become cultivated.
While these findings suggest that the Black Death was not as catastrophic as many historians argue, the authors of the new study did not propose a new figure for actual casualties from the pandemic. “We don’t feel in a position to make a guess,” said Timothy Newfield, a disease historian at Georgetown University and one of Izdebski’s collaborators.
Some independent historians said the new continent-wide study matches the results of their own research into specific European locations. For example, bioanthropologist Sharon DeWitte of the University of South Carolina found that skeletal remains from London during the period showed evidence of a modest number of casualties made by the pandemic. This led her to speculate whether this might have been the case with other parts of Europe.
“It’s one thing to make a reasonable assumption and quite another to present evidence, as these authors did,” DeWitte said. “It’s really interesting.”
But other experts were not convinced by the new study. John Aberth, author of “The Black Death: A New History of the Great Mortality,” said the study did not change his opinion that about half of Europe’s population died.
He said he doubted the plague could have spared entire regions of Europe while ravaging others.
“The regions were highly interconnected, even in the Middle Ages, by trade, travelers and migration,” said Aberth. “That’s why I don’t believe whole regions could have escaped the plague.”
Aberth also questioned whether the fact that a region began producing pollen from cultivated plants necessarily meant that its population was growing. He speculated that the people may have been wiped out by the Black Death, but that their place may have been taken by immigrants who occupied the empty lands.
“The arrival of migrants may have compensated for the demographic losses,” he suggested.
Izdebski acknowledged that there was migration in Europe at the time of the bubonic plague, but argued that the documented number of migrants was too low to replace half the population.
And he pointed out that huge waves of migrants would have had to have arrived from other parts of Europe whose populations had also allegedly been decimated by the Black Death.
“If hundreds of thousands of people had to arrive, where would they come from, if half the population everywhere would have died?” he asked.
Phoenix-based independent historian Monica Green has speculated that the Black Death may have been caused by two strains of the bacterium. Yersinis pestis, which may have caused different levels of devastation. the DNA of Yersinia pestis taken from medieval skeletons points to that possibility, she says.
In their study, Izdebski and his colleagues did not consider this possibility, but took into account a number of other factors, including the climate and population density of different parts of Europe. None of these factors, however, could explain the pattern they found.
“There is no simple explanation that can handle this, not even a set of simple explanations,” Izdebski said.
Translation by Clara Allain
