Somewhere in chapter 2, Kyle Harper remarks how historians have become unintentional beneficiaries of ongoing climate change, as scientists turn to palaeoclimatic records such as ice cores, tree rings, and sediments to understand fluctuations in earth’s climate. This bonanza of data allows historians a new way to look at past events. And thus was born the discipline of environmental history, which emphasizes the active role the natural environment can have on human affairs. In The Fate of Rome, Kyle Harper looks at one of those defining moments in human history, the decline and fall of the Roman empire, and the role of climate change and pandemics.

The first thing you’ll notice is that this is a chunky book. The narrative runs just short of 300 pages, but this is padded out with almost 100 pages of notes and references. Why this apparatus is so extensive becomes clear when reading the book; coverage is both thorough and nuanced, acknowledging the many different opinions of and interpretations by historians. Harper is not out to overthrow the established narrative, but rather to explain what knowledge of past climate change can add to the story as we know it.

This book covers the period of 200 BC to AD 700. The first 350 years of these saw the Roman empire at its maximum reach and prosperity. Effectively, the Romans got lucky and had a silent ally. Dubbed the Roman Climate Optimum, it was a period in which all the mechanisms that influence earth’s climate over varying timescales (orbital, solar and volcanic), colluded to produce a warm, wet and stable climate, rather different from today. This is something to keep in mind when reconstructing life at the time or trying to understand archaeological findings. For example, it allowed agriculture in areas that nowadays are unsuitable, as shown by remnants of wine presses found at high elevations.

But things were not to stay this way. Having both a dense population and road network, the Roman empire proved to be an ideal staging ground for the first pandemic, a mortality event known as the Antonine Plague of AD 165. Before introducing it, Harper does an excellent job explaining that, despite what we might think, the Romans lived with a constant background level of disease and mortality. Malaria was rife in Rome for example. But this plague was a pandemic of different proportions, and through the analysis of ancient DNA from human remains, most evidence points to smallpox as the culprit. Add questionable medical practices and the lack of germ theory, and you’ll understand how this epidemic swept through the Roman empire, killing an estimated 7-8 million people (10-20% of the population).

“Effectively, the Romans got lucky and had a silent ally.”

The Antonine plague was a heavy blow and marks a turning point, as the climate slowly started changing. The net effect of several interacting factors had been an anomalously long period of climate stability, keeping drought at bay. But with changes, the longer-term cycle of aridification started impacting the empire. This Roman Transitional Period (AD 150-450), as Harper calls it, saw yet another plague, the Plague of Cyprian, of which we still do not know the identity. In its wake followed chaos and death, with the empire fragmenting, and its imperial war machine, securing the frontiers, revolting. Incursions by barbarian hordes followed. Subsequent emperors just about managed to hold the fragments together.

Harper puts forward the interesting idea, which is gaining acceptance more widely, that a changing climate in Asia drove the nomadic Huns westwards from the Eurasian steppe, displacing other tribes, which in turn rocked up at the doorstep of an already weakened Roman empire. In AD 410 this led to the unbelievable finally happening. After a decade-long rampage, an army of Visigoths sacked Rome. Though the city was spared pillage and large-scale destruction, this massive defeat resonated through the empire. The western half disintegrated in the following decades, with power shifting to the new capital of Constantinople in the east.

The period from AD 450-700 is known as the Late Antique Little Ice Age and saw a drop in temperatures. Increased volcanic activity in AD 530-540 led to some of the coldest decades for millennia. It also was the harbinger of a new pandemic: bubonic plague. The bacterium Yersinia pestis is best known for the Black Death in the Middle Ages, but for 200 years it caused repeated and severe outbreaks of plague throughout the remains of the empire, causing more famine, chaos and instability, routinely killing off 50-60% of victims, and leaving no room for any meaningful recovery. Bit by bit, the imperial network disintegrated, leaving isolated pockets to fend for themselves, disconnected from trade routes and the protection of the Roman army. Constantinople, too, fell, as a new religion, Islam, was aggressively expanding its influence in the Middle East.

“[…] the Romans did not just vanish. Instead they went back to levels of technology and material culture not seen in centuries”

Though this was a period of depopulation, it’s important to keep in mind that the Romans did not just vanish. Instead they went through a period of tremendous transformation, returning back to levels of technology and material culture not seen in centuries, with many imported goods no longer making their way to Europe.

Not surprisingly, Harper ends with a reflection on what we today can learn from this story. The Roman Empire flourished for almost a millennium. The Industrial Revolution happened nary two centuries ago. Already, there are clear signs our climate is once again changing, and new microbes are evolving in the wild, with Ebola and Zika being examples of recent threats. For all our technological prowess, Harper warns we would do well to remember that we are not outside the sphere of influence of our climate. The only constant is change.

My knowledge of the Roman empire is quite limited, coloured by what I picked up from many an Asterix & Obelix album and Latin lessons in high school. Beyond the broad outline above, Harper covers many more details in his book, and the environmental lens he trains on this historical period makes for an absolutely fascinating read. I had to look up the occasional term in a dictionary (e.g. apotropaic: an adjective describing something though to have the quality to ward off evil or bad luck), but I nevertheless found the book very readable. My only gripe, nothing to do with the author, is that the 26 thematic maps in the book are printed in greyscale, often on half a page. This makes many details both hard to read and hard to tell apart from each other. Princeton University Press made this one of the lead titles in their Autumn 2017 catalogue, so I was surprised they didn’t put these maps in a colour plate section. That complaint aside, this is a great book that I can heartily recommend if you have even the slightest interest in ancient history.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

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