Origins of the fall of Rome

“On a scale the Romans were unable to understand or even imagine – from the microscopic to the global – the fall of the empire was a triumph of nature over human ambitions. Rome’s fate was the actors: emperors and barbarians, senators and generals, soldiers and slaves. But bacteria and viruses Volcanoes and solar cycles decided this too. Only in recent years have we come to have scientific tools that allow us to understand, even if often in passing, a great drama of environmental change of which the Romans were unaware…” kyle harper, “How the Roman Empire Collapsed. Climate, Disease, and the Fall of Rome”

The fall of the Roman Empire is a classic theme. You could even say an obsession. For decades we lived with this idea: barbarian invasions and internal political complications were the cause of the decline of the Roman great power.

Historian Kyle Harper offers another hypothesis. This explanation is due to solar radiation, microbes, volcanic eruptions, and climate changes.

In a book that received unanimous acclaim, he sketched a climatic history of the fall of the empire. A practice made possible by technological advances. Ice cores and tree rings are “natural archives,” he says, new data that can be combined with stories.

The story of a superpower's downfall due to climate risks, which gives a few ice ages and pandemics likely roles, clearly resonates with our times and contemporary concerns, from global warming to the AIDS or Covid epidemics. But these works and these “ecological” approaches to history, which explain even cultural phenomena, such as the cult of Apollo revitalized by the Antonine Plague, are also a subject of debate in the scientific community.

Harper is a representative of an important movement paving its way in the field of history. That's why he was invited to lecture at the Collège de France and hold a chair there, and that's why we invite him.

Blue sun

In the 6th century, Cassiodorus wrote that a blue sun had been observed. Procopius of Caesarea said that it resembles the sun during an eclipse. What were the effects of the sun on the fall of Rome? “This example is very interesting for climate history. For decades, written accounts that the sun appears dimmer were not taken seriously. It was NASA scientists who put the pieces of the puzzle together and took these human testimonies seriously. In recent decades, we have learned a lot about this event caused by volcanic eruptions. What we didn't know was that there had been two major volcanic eruptions. Eruptions are extremely powerful cooling mechanisms. When you change the system by one or two degrees, in a very short period of time, the consequences are completely unpredictable. In this case, the climate events themselves were a huge problem for communities. Harvests were poor, communities suffered, and within a few years – just two to three years – a massive pandemic developed. We know that these events, this climate episode, and this pandemic are closely linked. The consequences were intertwined with each other. Ultimately, this was perhaps the greatest crisis the Roman Empire had ever faced. By putting the pieces together, and understanding the environment as a big factor in human societies, this is where we arrive.“.

Natural archives

In this lesson at the Collège de France, Harper explains that historians generally do their research in records, letters, documents, and inscriptions. This means archives left by humans. Today we can read history in ice, wood, stone and sediment layers. Why can't we read it until now? “The irony is that the motivation behind this massive climate research is the crisis caused by humans. The climate system changes partly naturally, and we have only measured the relationships for a few hundred years. Thermometers were only invented in the 17th century. So how do we know, how do we know the history of climate without direct observation? Well, you have to look at the natural records, the indirect evidence. It is the history of the Earth that can be reconstructed from data hidden in ice sheets, such as in the polar caps of Greenland, and in trees, which are truly extraordinary archives, and what we find in minerals, and accumulations of minerals in caves.“.

Mix stories

Isn't there, however, an inherent danger in Kyle Harper's approach: the danger of determinism, that is, the belief that every climate event has a significant and unique impact on human history, and on the fate of humanity? “As a historian, we must always remain on guard against environmental determinism. But we must also be careful not to underestimate these environmental factors. I think the challenge facing historians is to integrate human factors with environmental factors. Climate change did not cause the fall of the Roman Empire. But climate change has put a severe strain on these communities. With human choices, human factors, political and tax systems, and the interaction between these systems, this is what makes history.“.

The Antonine Plague and political changes

The climate at first seems to have been quite favorable to the empire. We are talking about the optimal Roman climate. “Roman historians were not the ones who invented this term. This is paleoclimatology. It was Earth system scientists who realized that during the last centuries before Christ, up until the second century AD, there was an exceptionally stable phase in which solar energy was high and constant. This appears to be one of the most stable phases of the Holocene“We then distinguish several stages in the collapse of the empire. The first stage is perhaps that which unfolded during the reign of Marcus Aurelius, and which marks the first great difficulties of the empire. The period of the Antonine plague.”This is our first example of a clear link between a climate change moment and a pandemic. An episode of a very widespread infectious disease. A huge epidemic broke out, with an extremely high mortality rate. This is a very interesting event for historians, but we still do not know its cause. It's one of the interesting mysteries we're still trying to solve. But we saw that this epidemic was very widespread, that it shook this society severely, and that it caused and created a new period in Roman history.“How did Roman institutions react to the Antonine Plague?”The Roman system survived these crises. The Roman Empire did not collapse. It continued until the second century. There is a redistribution of power, demonstrating accountability of the Roman army. Very quickly, they truly had more power and played a greater role in choosing emperors, choosing emperors. The empire becomes more comprehensive. The grip of the small Italian elite was beginning to open up, and the empire became increasingly governed from certain provinces. This new system was implemented with shock“.