Reintroduction or European reservoir? – a key question for possible effects of 14th c. landscape history on the Black Death

A new article deals with the question of reintroductions of the Black Death from Asia and the role of reservoirs of Yersinia pestis in Europe. A database of historically recorded outbreaks of the plague is correlated with climate data from Central Asia as the main reservoir of the plague. As there is a correlation between climate change and outbreaks of the plague in Europe 15± 1 y, the authors see a mechanism starting with a situation, “when
the climate subsequently becomes less favorable, it facilitates the collapse of plague-infected rodent populations, forcing their fleas to find alternative hosts.” Such alternative hosts could be camels, which “are known to become infected relatively easy from infected fleas in plague foci, and can transmit the disease to humans.” Trading with caravans could transport the plague “across ∼4,000 km from the mountains of western Central Asia to the coast of the Black Sea”. The authors compare the transport rate of ∼333–400 km per year with that of the thrd pandemic in China ( ca 123 km per year) and the Black Death in Europe, which is however much faster (1330 km per year).

According to this model the plague of 1348/49 is in fact a reintroduction from Asia. This is remarkable, when thinking of the effect of landscape changes in Central Europe, which in fact created a situation, when anthropogenic alterations of the landscape provided a situation which had the potential to cause extrem weather, soil erosion and effects on rodents’ population. If there was no European reservoir of yersinia pestis at that time in Europe, the risk of an anthropogenic factor in the outbreak of the Black Death is significantly smaller (comp. Yersinia pestis – the missing ecological and historical dimension. Archaeologik [10.11.2011]. Attempting to take an ecological perspective on the Black Death is an important step also for a better understanding of the 14th c. crisis.

Boris V. Schmid; Ulf Büntgen; W. Ryan Easterday; Christian Ginzler; Lars Walløe; Barbara Bramanti; Nils Chr. Stenseth, Climate-driven introduction of the Black Death and successive plague reintroductions into Europe. PNAS Published online before print February 23, 2015 –  doi: 10.1073/pnas.1412887112

with supplements: http://www.pnas.org/content/suppl/2015/02/20/1412887112.DCSupplemental

Authors’ abstract
The Black Death, originating in Asia, arrived in the Mediterranean harbors of Europe in 1347 CE, via the land and sea trade routes of the ancient Silk Road system. This epidemic marked the start of the second plague pandemic, which lasted in Europe until the early 19th century. This pandemic is generally understood as the consequence of a singular introduction of Yersinia pestis, after which the disease established itself in European rodents over four centuries. To locate these putative plague reservoirs, we studied the climate fluctuations that preceded regional plague epidemics, based on a dataset of 7,711 georeferenced historical plague outbreaks and 15 annually resolved tree-ring records from Europe and Asia. We provide evidence for repeated climate-driven reintroductions of the bacterium into European harbors from reservoirs in Asia, with a delay of 15 ± 1 y. Our analysis finds no support for the existence of permanent plague reservoirs in medieval Europe.


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