- Adam Izdebski, Alessia Massi, and Timothy P. Newfield
- The Conversation*
In the popular imagination, the Black Death is the most devastating pandemic that has affected Europe. Between 1346 and 1353, it is believed that it reached almost, if not all, the corners of the continent, killing between 30% and 50% of the population.
This account is based on texts and documents written by state or church officials and other literate witnesses.
But, as with all medieval sources, the geographical coverage of this documentation is uneven. While some countries, like Italy or England, can be studied in detail, there are only vague hints about others, like Poland.
Not surprisingly, researchers have struggled to correct this imbalance and discover different ways to estimate the extent of mortality from the Black Death.
In our new study we have used 1,634 fossil pollen samples from 261 lakes and wetlands in 19 European countries. That large amount of material allowed us to compare the demographic impact of the Black Death across the continent.
The number of victims of the pandemic was not so universal as currently claimed, nor was it always catastrophic.
Lakes and wetlands are nature’s wonderful archives. They continually accumulate remains of living organisms, soil, rocks and dust. These deposits can record hundreds or thousands of years of environmental change.
We can take advantage of those archives by extracting cores and analyzing samples taken at regular intervals, from the top (present) to the bottom (past).
In our study we rely on pollen analysis.
Because pollen grains are made of a durable polymer and differ in shape from plants, they can be counted and identified in each sediment sample.
We are allowed reconstruct the local landscape and changes over time. They illuminate human land use and the history of agriculture.
For more than a century, paleoecologists – who study the ecosystems of the past – have accumulated data.
In various regions of the world, the amount of evidence available is overwhelming and certainly enough to raise questions about major historical events such as the Black Death.
Did their mortality affect land use? Did farm fields turn into pasture or were they abandoned and allowed to be repopulated?
If a third or half of the European population were to die out in a few years, one would expect a near collapse of the medieval cultivated landscape. Applying advanced statistical techniques to the available pollen data, we test this hypothesis, region by region.
The ecology of the black plague
We discovered that there were indeed parts of Europe where the human landscape shrank drastically after the arrival of the black plague, as in southern Sweden, central Italy and Greece.
However, in some regions, such as Catalonia or the Czech Republic, there was no perceptible decrease in human pressure on the landscape.
In others, such as Poland, the Baltic states, and the center of what is now Spain, labor-intensive farming raised, as colonization and agricultural expansion continued uninterrupted throughout the Late Middle Ages.
That means the mortality of the Black Death was neither universal nor universally catastrophic. If it had been, the sediment records of the European landscape would tell us.
This new narrative of a regionally variable Black Death fits well with what we know about how plague can spread to and between people, and how it can circulate in urban and wild rodents and their fleas.
That the plague has not equally devastated all European regions should not surprise us.
Not only will societies be affected and may respond differently, but we should not expect the plague to spread in the same way every time or that plague pandemics are easily maintained.
Plague is a disease of wild rodents and their fleas. Humans are accidental hosts, generally considered unable to sustain the disease for long.
Although how plague outbreaks break out of wild rodent reservoirs and spread to and within human populations is under study, we know in human societies that it can spread through a variety of means.
Most of the time, it is contracted through flea bites, but once successful infection occurs, multiple means of transmission may be involved, so human behavior as well as living conditions, lifestyle of life and the local environment, affect the ability to spread.
Although its transmission in the Black Death remains unclear, historians have tended to focus on rats and their fleas since the early 20th century, and assume that it behaved much the same in many places.
But rethinking the map and timeline of the pandemic, we also need to rethink how it spread. Local conditions would have influenced the spread of the plague and, therefore, its mortality and its effect on the landscape.
People’s way of life – between 75% and 90% of Europeans lived in the countryside – or the number, distance and means with which they traveled, could have influenced the course of the pandemic.
Cereal trade patterns, which would have helped the rats to move, could have been another important factor, as was the weather when the plague began.
The health of the victims and the regional burden of the disease were other variables, partially conditioned by the weather, not to mention nutrition and dietincluding the mere availability of food and its distribution.
Lessons from the pandemic
Our discovery of the impressive regional variability of the Black Death has consequences potentially beyond the study of the plague’s past. It should stop us from making quick generalizations about the spread and impact of the most infamous pandemic in history.
It should also change the way the black plague is used as a model for other pandemics. She may still be the “mother of all pandemics,” but what we think of as the Black Death is changing.
Our discovery could also prevent us from drawing easy conclusions about other pandemics, especially those that are less studied and with accounts based on fragmentary evidence.
Context is important. Economic activity can determine the routes of spread, population density can influence how fast and how wide a disease spreads, and the “behavior” of pathogens can differ between climates and landscapes.
Medical and popular theories of disease causation will determine human behavior, as trust in authorities will affect their ability to manage the spread of disease, and social inequalities will ensure disparities in the number of victims of an outbreak. .
Though no two pandemics are the samestudying the past can help us discover where to look for our own vulnerabilities and how to better prepare for future outbreaks.
But to begin to do so, we need to reassess past epidemics with as much evidence as we can.
*Adam Izdebski is a lead researcher at the Max Planck Institute for the Science of Human History, Alessia Massi is a research fellow at Sapienza University of Rome, and Timothy Newfield is a professor of environmental history and historical epidemiology at Georgetown University.
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