Saturday, October 27, 2018

"The Great Transition: Climate, Disease and Society in the Late-Medieval World"

A masterful review from Monica Green at Inference Magazine:
Bruce Campbell’s The Great Transition chronicles an important and gloomy historical moment. The two centuries between the 1260s and 1470s witnessed the collapse of international networks of exchange, multiple wars, economic contraction, repeated famines, and demographic decline. The single most profound event was what is still considered the most devastating pandemic of human history: the Black Death of the middle of the fourteenth century. In Europe and around the Mediterranean basin, mortality levels have been estimated at between forty and sixty percent. The 1470s were only a period of stabilization. The new world that the Great Transition ushered in was colder, wetter, and more disease ridden than any humans had ever known before. Historians of the early modern period have recognized the climatic period known as the Little Ice Age (LIA) for some time.1 For the history of medicine, no agreed-upon term has arisen for this regime of intense infectious diseases, which were in full global circulation after 1492. For plague in particular, it is now recognized that instead of seeing the Black Death as a singular event, we should instead recognize the 500-year period of plague infestation that it initiated in Eurasia and Africa as the Second Plague Pandemic.

The Great Transition
Campbell’s book has twelve tables, seventy-eight figures, most of them graphs, and a bibliography running forty-six pages. Campbell has always favored data-heavy analyses; his many decades of study on English agriculture were based on massive compilations of data on crop yields, and he has recently coauthored a comprehensive survey of the British economy from the thirteenth to nineteenth centuries.2 Agriculture is always dependent on weather, which in turn depends on climate cycles; this explains Campbell’s movement into climate history about ten years ago. The devastating effects of the Black Death on England, where population loss was accompanied by a massive decline in wealth, explain his interest in the pandemic. Campbell’s efforts in attempting to master the emerging fields of paleoscience that deal with climate and infectious disease will repay the dedicated reader.
The Black Death was not the only catastrophe Europe suffered in the fourteenth century. A whole generation of readers has the title and imagery of Barbara Tuchman’s A Distant Mirror: The Calamitous 14th Century seared into their conceptions of life in the late Middle Ages.3 Famines, the Hundred Years’ War, economic disruptions, and all manner of hardship made life in Europe, at least, distinctly unpleasant. Campbell looks at this same long fourteenth century, arguing that this 200-year period should be carved out from the previous periodization in climate history, which saw the warm period of the Medieval Climate Anomaly (MCA) leading straight into the LIA. For Campbell, a variety of climate-forcing factors and economic shifts argue for designating the Great Transition as its own separate period, with four distinct phases.
  • 1260s to 1330s: This period saw the end of the MCA, a prolonged, mostly warm period that began around 900 CE which, with one exception in the first half of the eleventh century, was likely due to a high solar irradiance. In the MCA, not only Europe but much of Eurasia flourished. Rising populations, increasing urbanization, an economy growing by leaps and bounds: never had the world seen so much sustained growth and cultural flourishing. The onset of the Wolf solar minimum signaled the end of this prolonged period.4 Combined with changing weather, many years in this period experienced pronounced rainfall at levels that had not occurred since the 1250s and would not occur again until the 1980s. The late thirteenth and early fourteenth centuries saw repeated catastrophes, including a sheep-scab epizootic in the 1270s and 1280s, the Great Northern European Famine of 1315–17, and a cattle panzootic of 1319–20. This period also saw a marked reduction of international trade, with severe shortages of bullion. 
  • 1340s to 1370s: The 1340s and early 1350s were, as Campbell remarks, “an almost uniquely disturbed and climatically unstable period when long-established atmospheric circulation patterns were on the cusp of lasting change.”5 The period was distinctly cold, and tree rings show a collective growth minimum. Extreme weather events stand out, such as the devastating Saint Mary Magdalene’s flood in central Germany in July 1342, which raised the Main to levels higher than have ever been documented since, and washed away the better part of topsoil in the region. Warfare, harvest failures, and famine all struck, virtually at once, followed by the great Black Death pandemic, 1346–1353. Despite a few years of climatic and economic alleviation in the 1350s, the plague’s return in the early 1360s ensured that population levels remained depressed. Campbell ventures an estimate of plague mortality of twenty-five million people in Europe, with figures in England indicating that at least one-third of the population perished, and, in certain regions, almost forty percent.6 The plague returned again around 1360, this time having a particularly pronounced effect on children born since the Black Death. It would return at least three more times before the century ended, and would, in fact, haunt most of Europe and the Mediterranean for the next three centuries. By the 1380s, Europe’s population had been reduced by half. 
  • 1370s to 1470s: During this period, climate conditions continued to deteriorate. The LIA followed a brief period of solar irradiance in the late fourteenth century, the so-called Chaucerian maximum. The Spörer minimum, ca. 1416–1534, had effects on the Indian Ocean monsoon, the Nile flood, and the North Atlantic oscillation, resulting in global temperature drops of 0.4–0.8°. The aerosols produced by the eruption of Mount Kuwae off the coast of Vanuatu around 1458 reinforced these trends. Europe remained in a demographic spiral, burdened by infectious disease, a depressed economy, and war. 
  • 1470s on: The Spörer solar minimum finally eased, and there was a slight alleviation of the intense cold. Campbell notes a demographic shift in Europe around 1500, when, even without any apparent cessation of the disease regime, population recovery, at least in northern Europe, led to levels approaching those before the Black Death. By this point, Portugal, allied with Genoa, had circumvented the trans-Saharan trade in gold and ivory and established its own direct ties with West Africa. It also began its expansion into the Atlantic, as did the Spanish and then the English. The Dutch, however, came out most successfully as Europe’s new economic power. This newly configured Europe, one where northern countries took over the economic power formerly wielded by Italy, had now adjusted to the new world the previous two centuries had made. In other words, the Great Transition was completed and the Old World had adjusted to the new climatic and economic balance.
The late medieval period is well-worn territory for Europeanist historians, and many of the political, economic, and cultural ruptures of the period are well-known. Yet the commonly cited signposts that medievalists and early modernists usually use to stake out their respective terrain now stand as just items in long lists of interconnected shifts, declines, and catastrophes in Campbell’s account. The fall of Constantinople to the Ottoman Turks in 1453, for example, signaling the end of Roman Byzantium, the last vestige of the Empire, is here nothing more than another falling domino. The majority of the book keeps its focus on England and the economic evidence Campbell knows best; when it ventures beyond, Europe still serves as its point of view. This narrow focus has its costs. Overall, Campbell presents a tight chronological narrative, moving between global forces that shift monsoon patterns and tree growth, and changes in the silver supply and the spice market, down to the level of microbes. Campbell often uses dramatic language: “the Rubicon had been crossed,” and, the “climatic regime had already passed the point of no return.”7 The transition Campbell is chronicling is, “big, complex, multi-faceted.”8 It was a transition, not a cycle.9 The buildup is long, and the identification of the consequences must be extended, too, because societies had to establish new socio-ecological equilibria to deal with a world that had been transformed.

The story, then, is complex and justifies the 200-year span that Campbell stakes out. But there is a climax, a tipping point, and it falls in the 1340s. Save for the eruption of the Samalas volcano in 1257, whose effects turn out to be less dramatic than initial assessments had predicted, all the changes leading up to the 1340s were gradual or iterative. Only one change seemed to be unique, and horrifically sudden, in that crucial fifth decade of the fourteenth century, and that was the arrival of plague.

The Plague
It seems a strange coincidence that the Middle Ages are bookended by two plague pandemics: the Justinianic plague, from ca. 541 to ca. 750, and the Black Death, which we usually date from 1347 to 1353 but which should now be seen as the beginning of the much longer Second Plague Pandemic. Historical periods are conventions we create, and the transition from antiquity to the Middle Ages, on the one hand, and then the Middle Ages to the early modern period, on the other, were fixed in historiography long before questions about the environment or history of disease loomed large. Yet both pandemics share more similarities than could have been imagined even a decade ago, which suggest why they should have been implicated in two of the greatest turning points in Afro-Eurasian history. Not simply were both caused by the same organism, Yersinia pestis, but climate science confirms that both emerged in periods of pronounced, and quite sudden, global cooling. Molecular genetics suggests that both issued out small pockets of long-term animal infestation in the central Eurasian steppe, or perhaps a region at the edge of the deserts of the Qinghai–Tibet Plateau, areas now part of western China and eastern Kyrgyzstan. The assumption that plague emerged out of arid central Asia is at the core of Campbell’s analysis, since he ties its emergence to a sudden period of drought in the 1250s, which followed several decades of exceptionally high moisture. Alternatively, he suggests that plague erupted during a subsequent drought in the 1290s, which in turn was reinforced by a subsequent pluvial period in the 1310s.10 The important point to note here is Campbell’s willingness to ascribe the initiation of the most devastating pandemic in history to two different points in time.

The issue is not that Campbell hasn’t been able to settle on a specific date; that would be difficult in the extreme, since we are talking about events transpiring between fleas and rodents in the wild. The issue is that, since he wishes to place these events in central Asia, it matters considerably whether they had a hundred, fifty, or only as little as thirty years to generate effects 4,500 kilometers away in the region of the Black Sea. And whether the interval was long or short, there is also the question of why the path of spread would have been unidirectional, when we would expect a radiating pattern out of a central focus. Since he believes that the spreading outbreak covered the longest part of its journey, the 3,300 miles from Kyrgyzstan to the Black Sea, in between eight and twelve years,11 both the speed and the unidirectionality become problematic. How does plague move across a landscape? How much time does it take? And how much genetic change should we expect to have occurred in relation to time elapsed? The first questions have been asked repeatedly in historiography about the Black Death; the third is one we have only been able to pose in the past few years. Clearly, the wet environment of much of the thirteenth and fourteenth centuries, which Campbell has documented persuasively for Asia and Europe and which was reinforced by the sudden cold of the 1340s, is well suited for sustaining continued plague outbreaks, and for allowing plague to focalize in adjacent areas, finding new pockets of burrowing rodents to afflict in slow-burning enzootics. But sustaining plague as a local enzootic, and accounting for locally radiating epizootics, is different from igniting a pandemic 4,500 kilometers away. The genetics is what Campbell is using to place the Black Death’s origin in central Asia.12 But the genetics is also what complicates his scenario....MUCH MORE
And some of the correspondence regarding the review:
         by Daniel Curtis and Joris Roosen, reply by Monica Green