At some time or another, every historian of Rome has been asked to say where we are, today, on Rome’s cycle of decline. Historians might squirm at such attempts to use the past but, even if history does not repeat itself, nor come packaged into moral lessons, it can deepen our sense of what it means to be human and how fragile our societies are.
In the middle of the second century, the Romans controlled a huge, geographically diverse part of the globe, from northern Britain to the edges of the Sahara, from the Atlantic to Mesopotamia. The generally prosperous population peaked at 75 million. Eventually, all free inhabitants of the empire came to enjoy the rights of Roman citizenship. Little wonder that the 18th-century English historian Edward Gibbon judged this age the ‘most happy’ in the history of our species – yet today we are more likely to see the advance of Roman civilisation as unwittingly planting the seeds of its own demise.
Five centuries later, the Roman empire was a small Byzantine rump-state controlled from Constantinople, its near-eastern provinces lost to Islamic invasions, its western lands covered by a patchwork of Germanic kingdoms. Trade receded, cities shrank, and technological advance halted. Despite the cultural vitality and spiritual legacy of these centuries, this period was marked by a declining population, political fragmentation, and lower levels of material complexity. When the historian Ian Morris at Stanford University created a universal social-development index, the fall of Rome emerged as the greatest setback in the history of human civilisation.
Explanations for a phenomenon of this magnitude abound: in 1984, the German classicist Alexander Demandt catalogued more than 200 hypotheses. Most scholars have looked to the internal political dynamics of the imperial system or the shifting geopolitical context of an empire whose neighbours gradually caught up in the sophistication of their military and political technologies. But new evidence has started to unveil the crucial role played by changes in the natural environment. The paradoxes of social development, and the inherent unpredictability of nature, worked in concert to bring about Rome’s demise.
Climate change did not begin with the exhaust fumes of industrialisation, but has been a permanent feature of human existence. Orbital mechanics (small variations in the tilt, spin and eccentricity of the Earth’s orbit) and solar cycles alter the amount and distribution of energy received from the Sun. And volcanic eruptions spew reflective sulphates into the atmosphere, sometimes with long-reaching effects. Modern, anthropogenic climate change is so perilous because it is happening quickly and in conjunction with so many other irreversible changes in the Earth’s biosphere. But climate change per se is nothing new.
The need to understand the natural context of modern climate change has been an unmitigated boon for historians. Earth scientists have scoured the planet for paleoclimate proxies, natural archives of the past environment. The effort to put climate change in the foreground of Roman history is motivated both by troves of new data and a heightened sensitivity to the importance of the physical environment. It turns out that climate had a major role in the rise and fall of Roman civilisation. The empire-builders benefitted from impeccable timing: the characteristic warm, wet and stable weather was conducive to economic productivity in an agrarian society. The benefits of economic growth supported the political and social bargains by which the Roman empire controlled its vast territory. The favourable climate, in ways subtle and profound, was baked into the empire’s innermost structure.HT: I Kaminska, FT Alphville's Further Reading post, Dec. 17.
The end of this lucky climate regime did not immediately, or in any simple deterministic sense, spell the doom of Rome. Rather, a less favourable climate undermined its power just when the empire was imperilled by more dangerous enemies – Germans, Persians – from without. Climate instability peaked in the sixth century, during the reign of Justinian. Work by dendro-chronologists and ice-core experts points to an enormous spasm of volcanic activity in the 530s and 540s CE, unlike anything else in the past few thousand years. This violent sequence of eruptions triggered what is now called the ‘Late Antique Little Ice Age’, when much colder temperatures endured for at least 150 years.
This phase of climate deterioration had decisive effects in Rome’s unravelling. It was also intimately linked to a catastrophe of even greater moment: the outbreak of the first pandemic of bubonic plague.
Disruptions in the biological environment were even more consequential to Rome’s destiny. For all the empire’s precocious advances, life expectancies ranged in the mid-20s, with infectious diseases the leading cause of death. But the array of diseases that preyed upon Romans was not static and, here too, new sensibilities and technologies are radically changing the way we understand the dynamics of evolutionary history – both for our own species, and for our microbial allies and adversaries....MORE
The author of this piece uses a Thomas Cole painting to illustrate the Aeon article but personally I think Canaletto or in this case his nephew, Bellotto, catches more of the "Man, what happened?" vibe:
