A recent study published in the journal Nature Ecology & Evolution, co-authored by Professor Siim Veski from the Department of Geology of Tallinn University of Technology, Senior Research Scientists Anneli Poska and Triin Reitalu and researcher Normunds Stivrinš, shows the importance of a cross-sectoral approach to understanding both past and present pandemics.

What does pollen tell us about the past? Quite a lot!

Pollen analysis is a discipline that studies plant pollen and spores. As 14th-century Europe was a predominantly agrarian society, the success and failure of the farming economy is reflected in the pollen of cultivated plants. As a result of this, the pollen method is a powerful tool for discovering the demographic effects of the Black Death: before the industrial age, local landscapes were mainly influenced by people living there, either engaged in agriculture or construction work.

In order to estimate mortality caused by plague in different regions of Europe using the Big Data Palaeoecology (BDP) method, the study used data obtained from pollen cross-sections from 19 European countries. To do this, the researchers analysed thousands of samples from before and after the plague epidemic. This made it possible to clarify which plants grew in which regions to what extent and whether agricultural activity was consistent in each of the areas studied or was there a hiatus at a certain time. It also studied whether wild plants were taking over the cultivated landscape when human activity in the area was in a decline due to the plague.

Scandinavia hit hard, Eastern Europe escaped the worst

The results of the study showed that the impact of the Black Death on Europeans' mortality rates in the mid-14th century varied quite widely. Some regions* suffered greatly from the devastation of the pandemic, while others fared much better.

The study showed a sharp decline in agriculture (i.e. decrease in human activity) in Scandinavia, France, southwestern Germany, Greece and central Italy, which supports the high mortality rates proven in medieval sources. At the same time, the study showed that in some regions, life continued quite normally – including much of Central and Eastern Europe, as well as many parts of Western Europe such as Ireland and the Iberian Peninsula. In other words, these areas were not drastically affected by the Black Death.

Who comprised the international research group?

The research group consisted of an international team of researchers led by the Palaeo-Science and History group of the Max Planck Institute (an organisation that unites German research institutes), including four researchers from Tallinn University of Technology.

The researchers analysed pollen samples at 261 different sites across 19 modern European countries to explain how Europe's landscapes and agricultural activities changed between 1250 and 1450, 100 years before and up to 100 years after the Black Death pandemic. Considered to be the most devastating plague pandemic in human history, the Black Death is thought to have originated in China and spread to Europe along trade routes.

Pandemics require contextual knowledge

One reason to the recent results being so surprising is that many of the quantitative sources previously used to study the Black Death come from urban areas. Although people in these areas were able to collect and store information about the disease, they lived in close quarters and in poor sanitation. In fact, more than 75% of Europe's population lived in rural areas and not cities in the mid-14th century. This study shows that in order to understand the actual mortality rate in each individual region, data must be collected and reconstructed from the sites where people actually mostly lived, i.e. across the European agricultural landscape, using a method of monitoring changes in cultural landscapes.

Adam Izdebski, head of the Palaeo-Science and History research group at the Max Planck Institute, stresses that there is no single "pandemic model" or "plague outbreak model" that can be applied anywhere at any time, without considering the context. Unfortunately, pandemics are complex phenomena with regional and local histories. "We have seen this with COVID-19 and now with the Black Death."

Summary – Cultural, economic and climatic factors also have an impact

The wide variation in Black Death mortality across Europe shows that the plague was a dynamic disease whose spread and impact were mediated by cultural, ecological, economic and climatic factors. In any case, it is hoped that in the future, more and more studies will make use of palaeoecological data as a means to understanding how these variables influence past and present pandemics.

*Read the scientific article (and see photos of the BDP method and more detailed maps of the spread of the Black Death) "Palaeoecological Data indicates land-use changes across Europe linked to spatial heterogeneity in mortality during the Black Death pandemic" in the latest issue of Nature Ecology & Evolution.