How much were medieval Italians themselves responsible for the food shortage that by late spring 1347 was affecting about half the population of Tuscany, for the onset that summer in Sicily and Genoa of an epidemic which would in a few years kill half or more of the European population, or for the buildings smashed and hundreds of deaths in Venice and further northeast in an earthquake of January 1348? Ought those events be related to unsurpassed flooding across central Europe in July 1342, and the crash of English grain yields to 40 per cent of normal in 1348–52?

Did the spread of an exotic animal, the rabbit, in thirteenth-century England and the Low Countries have anything to do with the simultaneous extirpation of native wild boar from Britain? And the arrival of an exotic fish, the common carp, in France at the very time that native salmon were vanishing from streams of coastal Normandy? Was any of this change to biodiversity connected to medieval classification of the beaver as a fish?