I recently read this interesting book, The Fate of Rome, Climate, Disease, and the End of an Empire by Kyle Harper: https://press.princeton.edu/titles/11079.html. Historically, most analyses of the fall of the Roman Empire rely on corruption, the breakdown of collegiality and bad governance, barbarian invasions and many other such factors. Harper’s thesis is that climate change, old, new and emerging diseases, and the expansion of the Empire contributing and reacting to the former and opening up new vectors for the latter, created the conditions by which the Empire was greatly weakened and led to its ultimate demise.
Through meticulous research of historical records and scientific studies of ice cores, tree rings, fossils, exhumed bodies and other biomedical research findings, Harper shows how the climate both greatly aided the rise of Rome and its expansion during the Roman Climate Optimum, and later significantly undermined its stability through global cooling from a dimming of the sun through natural cycles, volcanic activity blotting out what sunshine did reach the Earth, crop failures, and aridification. In the good times, the Romans were well fed and nourished, the granaries were full to provide for the poor, and population increased, all enabling strong immune systems to fend off the usual diseases, a relatively happy populace, and full legionary ranks to defend against the Empire’s enemies. But the Empire’s good times and expansion also contained the seeds of its demise, for overreliance on a munificent climate led to deforestation, and the very expansion of Rome into new lands and contact with hitherto unknown peoples, wildernesses and jungles, exposed new pathogens or awoke old ones, and enabled their spread throughout the Empire via its excellent roads, infrastructure and trading networks. When the climate no longer played nice or natural disasters wrought havoc, people began to starve, their immune systems weakened, and they become susceptible to disease, both old culprits like smallpox, and devastating hemorrhagic fevers previously unknown, including possibly the Ebola virus, which may have been responsible for the Plague of Cyprian. This in turn led to the decimation of the population, thinning out the ranks of the army, and leaving the frontiers prone to barbarian incursions. Barbarians were already increasing pressure on the Empire from fleeing the Huns who were then flooding into their territories from the East. Indeed, the Huns themselves may have begun their westward migration to escape the dust bowl in their native lands from adverse climate change. And this also led to the rise of end of times eschatological religion like Christianity and eventually Islam that severely undermined the social fabric of the pagan Empire. Moreover, all of this calamity was happening around the same time, feeding on itself in a vicious cycle from which there was no escape. Human institutions and civilization put up a surprisingly strong fight, but then came the Bubonic Plague travelling effortlessly along remaining trade routes. That was the last straw. Perhaps as much as half of humanity was dispatched from the Earth during this first known episode of Black Death. With not enough people around to operate the machinery of society, let alone Empire, all collapsed and the Dark Ages began.
This was a pretty fascinating and scary read. Of course, the implications for today are not totally straightforward since we now have modern medicine and genetic sequencing to provide a much more comprehensive and intensive understanding of, and better treatments for, diseases. However, we are in the midst of another episode of climate change with unknown effects despite sophisticated computer modelling, and possibly one of the worst extinction events in Earth history – the Holocene or Anthropocene Extinction, severely stressing the ecological system. In addition, the world has never been more globalized with the free movement of peoples, including their germs. Who knows what could happen. Despite our pride in our achievements and supposed mastery over nature, we are still at the mercy of the Earth for our survival. Things can go wrong, and when they do, this book shows how fast it can happen. This is a warning to us all!