Volcanic activities may have contributed to the spread of the Black Death in Europe in the 14th century, a disease that destroyed part of the continent’s population. This hypothesis is contained in a new study published on Thursday (4) in the journal Communications Earth & Environment from Nature.
It is estimated that the Black Death pandemic killed millions of people at the time. Some studies indicate that there are more than half of Europe’s population, but a more recent survey conducted in 2022 indicated that these data are exaggerated.
The authors of the new research suggest that volcanic eruptions led to lower temperatures between 1345 and 1347. This scenario in turn affected grain farms, leading to the intensification of trade between regions in Asia and Europe. In this context, ships carrying grains transported fleas infected with bacteria to European countries.
Other research has shown that Yersinia pestis It originates from wild rodents in Central Asia and reached Europe via the Black Sea region. However, there is little evidence about the factors that influenced the spread of the disease between Central Asia and Europe from 1347 onwards, a question the new study sought to answer.
To achieve this, the research relied on analyzes of paleoclimatology, the field that seeks to understand the Earth’s climate at different moments in history. In the study, the authors paid attention to historical reports of a volcanic eruption – or group of unconfirmed eruptions – that occurred around the year 1345.
Scientists found evidence that shortly after this volcanic phenomenon there were records of cold waves in Europe, especially in the Mediterranean region. The blue rings on trees in the Pyrenees region of Spain were crucial in arriving at this conclusion. It indicates an anomaly in the development of these trees, as their wood is not fully fused.
According to the authors, it was this sudden drop in temperature, especially in the middle of 1345 and 1346, that caused such a failure in tree formation, resulting in the appearance of the rings. The historical sources analyzed in the study also contain reports of particularly cold summers in these years.
“The tree ring data give me confidence that my written sources are reporting the facts when describing meteorological anomalies,” said Martin Bausch of the Leibniz Institute for the History and Culture of Eastern Europe (Germany), author of the new study.
“On the other hand, written sources may make statements about seasons for which growth rings provide no information,” he added.
Hunger and black death
The climate disturbance associated with the volcanic eruption was associated with decreased grain production. This scenario in turn culminated in a wave of severe famine between 1345 and 1347, especially in the region around the Mediterranean. The authors suggest that for this reason, some of the maritime powers of the Italian peninsula, such as Genoa, Venice and Pisa, solved the problem by importing grain from the Mongols around the Black Sea in 1347.
“This famine-induced shift in long-distance grain trade not only prevented large parts of Italy from starving to death, but introduced plague bacteria via grain shipments to Mediterranean ports and led to its rapid spread throughout much of Europe,” the authors state in the paper.
The finding that temporary climate change caused by volcanic activities accelerated the spread of the Black Death in Europe is relevant because it indicates how many factors influenced the spread of disease.
In Bausch’s assessment, it is important to understand the Black Death as a complex system, in which various elements were interconnected. “Plague bacteria are fundamentally unchanged, nor are their harmful effects and speed of spread. Through this study, we hope to question assumptions such as ‘same pathogen, same effect.’ In other words, the pathogen will not necessarily have the same outcome in every context, because other aspects influence the spread of the disease.”