The Roman Empire and climate change: How a changing climate plagued the empire with diseases

In a recent study published in Science Advances, scientists have discovered a relationship between a change in climate and outbreaks of pandemics during the Roman Empire. One of the most famous plagues, the Bubonic Plague, also known as the Plague of Justinian, killed about half of the Roman Empire population in the 6th century CE. Elsewhere across the Mediterranean, tens of millions lost their lives to the disease.

Showing signs of symptoms

The disease associated with the Bubonic Plague began with a fever before making its way to swelling in the groin and armpits. In some cases, it would lead to a coma and eventually death. There was no cure for this, and no remedy of any kind would help.

This new study, based on ten years of research, links this plague and other Roman Empire pandemics to climate change. Outbreaks of major plagues correspond to cold, dry weather periods over the Italian peninsula. These changes in climate put strain on Roman society, and showed how fragile it can be when it cannot handle what climate change brings.

The research shows that temperatures were 3 degrees Celsius (37.4 degrees Fahrenheit) lower than the high temperatures from previous centuries during years of plagues. These cooler temperatures coincided with the Antonine Plague from 165 CE to 180 CE, the Plague of Cyprian from 215 CE to 266 CE, and the pandemic that began with the Plague of Justinian from 541 CE to 549 CE and lasted until about 766 CE.

Piecing the puzzle together

Unfortunately, temperature records do not go this far back. In order to figure out what the temperature was like during this time, scientists use a method called ‘proxies’. Proxies include looking at tree rings and ice cores. However, tree rings have not yet shown Italy’s climate during the Plague of Justinian, and ice samples are not found in Italy because it is too far south.

Scientists had to use another proxy method: dinoflagellates. These are fossilized shell-like cysts from microorganisms in seafloor sediments from the Gulf of Taranto. The dinoflagellates provide information on whether the sea temperature increased or decreased. Depending on whether the temperature increased or decreased, the species of the dinoflagellates would change. This information allowed scientists to reconstruct the climate of southern Italy between 200 BCE and 600 CE.

Impacts of a changing climate

Though the change in temperature had a part in the pandemics, it was not the sole reason for these outbreaks. The course of a changing climate causes society to destabilise. There’s a decline in food and an increase in rats, mosquitoes and other pests.

The causes of the diseases for the other major pandemics of the Roman Empire, the Antonine Plague and the Plague of Cyprian are still unknown. It can be assumed that natural climate oscillations had a part in these plagues as well.

Looking at the climate proxies from other parts of the world during this same time period, global temperatures were all-around cooler. This is possibly due to a major volcano eruption.

The research from this study shows a correct correlation between climate changes and disease outbreaks. John Haldon, of Princeton University, says this is a good example of scientists and historians working together to cross-check and verify history.

Reference:

Metcalfe, Tom. “The Roman Empire’s Worst Plagues Were Linked to Climate Change.” Scientific American. https://apple.news/AYQRo7n-xTh-qybHwOjTjnQ