The Big Chill and the Eastern Mediterranean
What are these developments? One is the rise of nomadic powers, such as the Seljuqs in the Middle East, the Pechenegs in the Byzantine Empire, and the Banu Hilal in North Africa. Multiple dynasties fell or were weakened with the collapse of bureaucracies and the agrarian base to sustain organized military power. Major cities witnessed a decline in their population and infrastructure, marking the sharp final decline of the urban life developed in the region during the Hellenistic period. Finally, population shifts, both in-migration and out-migration, led to religious change as Muslim nomads took the place of Christian peasants in agriculturally marginal regions.
Some will probably accuse Ellenblum of environmental determinism, but this is not his argument. In his own words:
Civilizations are altered and transformed by calamities, although they usually succeed in finding, when the crisis is over, ways to reconstruct new stable societal structures and a new equilibrium that resemble, to a certain degree, the pre-calamity social order. Differences between pre- and post-calamity cultures, however, are often discerned.In other words, in periods of environmental catastrophe, people adapt in a variety of ways, and even when the catastrophe is over, those ways continue to exist and leave their own historical legacies, whether in demographic shifts, institutions, or settlement structures. The end result of this book isn't that the reader who knows the material will learn about new developments, but instead that he or she will see the climate shift as a common thread underlying them all, and as a result better perceive the role of the environment in history.