Climate-driven introduction of the Black Death and successive plague reintroductions into Europe
- Boris V. Schmida,1,
- Ulf Büntgenb,c,d,
- W. Ryan Easterdaya,
- Christian Ginzlerb,
- Lars Walløee,
- Barbara Bramantia, and
- Nils Chr. Stensetha,1
- aCentre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, NO-0316 Oslo, Norway;
- bDendroecology, Landscape Dynamics, Swiss Federal Research Institute for Forest, Snow and Landscape, CH-8903 Birmensdorf, Switzerland;
- cOeschger Centre for Climate Change Research, University of Bern, CH-3012 Bern, Switzerland;
- dGlobal Change Research Centre AS CR, v.v.i., CZ-60300 Brno, Czech Republic; and
- eDepartment of Physiology, Institute of Basic Medical Sciences, University of Oslo, NO-0372 Oslo, Norway
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Edited by Kenneth W. Wachter, University of California, Berkeley, CA, and approved January 28, 2015 (received for review July 9, 2014)
Significance
The second plague pandemic in medieval Europe started with the Black Death epidemic of 1347–1353 and killed millions of people over a time span of four centuries. It is commonly thought that after its initial introduction from Asia, the disease persisted in Europe in rodent reservoirs until it eventually disappeared. Here, we show that climate-driven outbreaks of Yersinia pestis in Asian rodent plague reservoirs are significantly associated with new waves of plague arriving into Europe through its maritime trade network with Asia. This association strongly suggests that the bacterium was continuously reimported into Europe during the second plague pandemic, and offers an alternative explanation to putative European rodent reservoirs for how the disease could have persisted in Europe for so long.
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.
Footnotes
- ↵1To whom correspondence may be addressed. Email: boris.schmid{at}gmail.com or n.c.stenseth{at}ibv.uio.no.
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Author contributions: B.V.S. designed research; B.V.S. and U.B. performed research; B.V.S., U.B., W.R.E., L.W., B.B., and N.C.S. analyzed data; B.V.S., U.B., W.R.E., L.W., B.B., and N.C.S. wrote the paper; C.G. contributed the plague dataset; B.V.S., U.B., and C.G. compiled and merged the plague and/or climate datasets; W.R.E. compiled the map of current plague foci; and B.V.S., U.B., W.R.E., L.W., B.B., and N.C.S. provided the theoretical, genetic, and historical interpretation.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission.
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This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1412887112/-/DCSupplemental.
Freely available online through the PNAS open access option.
