The fall of the roman empire from plagues and climate change

Preface. This is a book review of “The Fate of Rome Climate Disease and the End of an Empire” by Kyle Harper, which shows the brutal effects of plagues, climate change, and their joint interaction on the Roman Empire.

But there were many more reasons for collapse not mentioned in this book, such as deforestation (A Forest Journey: The Story of Wood and Civilization by John Perlin, topsoil erosion (Dirt: The Erosion of Civilizations by David Montgomery), and barbarian invasions (“The Fall of Rome: And the End of Civilization” and “Empires and Barbarians: the fall of Rome and the birth of Europe”.

Alice Friedemann  author of “When Trucks Stop Running: Energy and the Future of Transportation”, 2015, Springer and “Crunch! Whole Grain Artisan Chips and Crackers”. Podcasts: Practical Prepping, KunstlerCast 253, KunstlerCast278, Peak Prosperity , XX2 report


Kyle Harper. 2017. The Fate of Rome Climate Disease and the End of an Empire. Princeton University Press.

How the Antonine plague from 165 to 180 AD affected the Pagan cults

To the ancient mind, plague was an instrument of divine anger. The Antonine Plague provoked spectacular acts of religious supplication at the civic level, fired by the great oracular temples of the god Apollo. The emperors started minting a new image on the currency, invoking “Apollo the Healer.” Religious solutions were desperately sought in Rome.

Pagan philosopher Porphyry blamed the insolence of the Christians for this health catastrophe. “And they marvel that the sickness has befallen the city for so many years, while Asclepius and the other gods are no longer dwellers among us. For no one has seen any succor for the people while Jesus is being honored.” Valerian implemented measures that were unequivocally aimed at hunting out Christians.

The rise of Christianity from the Cyprian plague 249-262 (ebola or smallpox)

This plague was instrumental in making Christianity popular, because the pagan religions did nothing for pandemic victims.  But because Christianity was able to forge kinship-like networks among perfect strangers based on an ethic of sacrificial love, Christian ethics turned the chaos of pestilence into a mission of aid. The vivid promise of the resurrection helped convince the faithful not to fear of death. Priests pleaded for them to show love to the enemy, so they helped everyone, pagans and Christians alike. The compassion was conspicuous and consequential. Basic nursing of the sick can have massive effects on case fatality rates; with Ebola, for instance, the provision of water and food may drastically reduce the incidence of death. The Christian ethic was a blaring advertisement for the faith. The church was a safe harbor in the storm.  The traditional civic cults lost favor.

So much death and the alternative of religious life made it hard to find soldiers

The empire’s fortunes reached a low tide in the AD 260s. The cities were never quite the same; even the healthiest late antique cities were smaller than they had formerly been, and in aggregate, even after the recovery, there were simply fewer major towns. The old days when army recruitment could be handled with a light touch were forever gone.

The fourth-century state had to contend with at least one truly novel alternative to military service: the allure of the religious life for men who might have heeded the call to arms. “The huge army of clergy and monks were for the most part idle mouths.” By the end of the fourth century, their total number was perhaps half the size of the actual army, a not inconsiderable drain on the manpower reserves of the empire. The civil service was also an attractive, and safe, career. The vexing issue of military recruitment in the fourth century was not directly a demographic problem.

Supply chains played a role in spreading disease

Supply chains and manufacturing were extensive. For example, consider the accoutrements of soldiers. The Roman soldier carried arms manufactured in over three dozen specialized imperial factories spaced across three continents. Officers wore bronze armor, embellished with silver and gold, made at five different plants. Roman archers would have used bows made in Pavia and arrows made in Mâcon. The foot soldier was dressed in a uniform (shirt, tunic, and cloak) made at imperial textile mills and finished at separate dye-works. He wore boots made at a specialized manufactory. When a Roman cavalryman of the later fourth century rode into battle, he was mounted on a mare or gelding that had been bred on imperial stud farms in Cappadocia, Thrace, or Spain. The troops were fed by a lumbering convoy system that carried provisions across continents in mind-boggling bulk. The emperor Constantius II ordered 3 million bushels of wheat to be stored in the depots of the Gallic frontier and another 3 million bushels in the Alps, before moving his field army to the west.

These extensive supply chains helped to spread the Antonine and Cyprian pandemics, followed by one of the worst pandemics in 542 AD from the plague. The fusion of global trade and rodent led to the greatest disease event human civilization had ever experienced.  The plague is an exceptional and promiscuous killer. Compared to smallpox, influenza, or a filovirus, Y. pestis is a huge microbe, lumbering along with an array of weapons. But, it is in constant need of a ride.

The plague moved at two speeds: swiftly by sea and slowly by land. The mere sight of ships stirred terror.  Once infected rats made landfall, the diffusion of the disease was accelerated by Roman transportation networks. Carts and wagons carried rodent stowaways along Roman roads. It could spread anywhere that rats could travel.

Climate change and the Huns

The 4th-century was a time of mega-drought. The two decades from ca. AD 350 to 370 were the worst multi-decadal drought event of the last two millennia. The nomads who called central Asia home suddenly faced a crisis as dramatic as the Dust Bowl. The Huns became armed climate refugees on horseback. Their mode of life enabled them to search out new pastures with amazing speed. In the middle of the fourth century, the center of gravity on the steppe shifted from the Altai region (on the borders of what is today Kazakhstan and Mongolia) to the west. By AD 370, Huns had started to cross the Volga River. The advent of these people on the western steppe was momentous, terrorizing the tribes north of Italy, who fled to the Roman Empire in great numbers to escape them (for a longer explanation of the effect of the Huns, see my Book review of “The Fall of Rome: And the End of Civilization” and “Empires and Barbarians: the fall of Rome and the birth of Europe”).

They brought new cavalry tactics that terrorized the inhabitants of the trans-Danubian plains. Their horses were ferociously effective. In the words of a Roman veterinary text, “For war, the horses of the Huns are by far the most useful, by reason of their endurance of hard work, cold and hunger.” What made the Huns overwhelming was their basic weapon, the composite reflex bow.

The Justinian Plague (541 to 749 AD)

Justinian reigned as emperor from AD 527 to 565. Less than a decade into his reign, he had already accomplished more than most who had ever held the title. The first part of his reign was a flurry of action virtually unparalleled in Roman history. Between his accession in AD 527 and the advent of plague in AD 541, Justinian made peace with Persia, reattached vast stretches of the western territories to Roman rule, codified the entire body of Roman law, overhauled the fiscal administration, and executed the grandest building spree in the annals of Roman history. He survived a perilous urban revolt and tried to forge orthodox unity in a fractious church, through his own theological labors.

In the spring of 542 AD the plague appeared for the first time (Yersinia pestic) in the capital Constantinople.   For the next 23 years it became difficult to find and field armies. Taxes rose to unseen heights.  There have been two major plague pandemics since then, the Black Death in AD 1346–53, which lasted nearly 500 years, and the third in 1855 AD in Yunnan China and spread globally.

The dependence of the imperial system on the transport and storage of grain made the Roman Empire a heaven for the black rat.

It required one last twist of fate for the bacterium to make its grand entrance into the Roman world. The Asian uplands had prepared a monster in the germ Y. pestis. The ecology of the empire had built an infrastructure awaiting a pandemic. The silk trade was ready to ferry the deadly package. But the final conjunction, what finally let the spark jump, was abrupt climate change. The year AD 536 is known as a “Year without Summer.” It was the terrifying first spasm in what is now known to be a cluster of volcanic explosions unmatched in the last three thousand years. Again in AD 540–41 there was a gripping volcanic winter. As we will see in the next chapter, the AD 530s and 540s were not just frosty. They were the coldest decades in the late Holocene. The reign of Justinian was beset by an epic, once-in-a-few-millennia cold snap, global in scale.

One thing is certain: the relation between climate and plague is not neat and linear. As with so many biological systems, it is marked by wild swings, narrow thresholds, and frenzied opportunism. Rainy years foster vegetation growth, which in turn sparks a trophic cascade in rodent populations. In excess, water can also flood the burrows of underground rodents and send them scurrying for new ground. Population explosions stir the emigration of rodents in search of new habitats.

Given that there is a strong correlation between volcanism and El Niño, the volcanic eruptions of the AD 530s may have stirred the Chinese marmots or gerbils carrying Y. pestis out of their familiar subterranean colonies, triggering an epizootic that reached the rodents of the seaborne trade routes heading west.

The first victims were the homeless. The toll started to rise. “…the mortality rose higher until the toll in deaths reached 5,000 a day, then 10,000, and then even more.” John’s daily counts are similar. He estimated from 5000 rising to 7000, 12000 and 16000 dead per day. At first, there remained a semblance of public order. “Men were standing by the harbors, at the crossroads and at the gates counting the dead.” According to John, the grisly tally continued until 230,000 had been numbered. “From then on the corpses were brought out without being counted.” John reckoned that over 300,000 were laid low. A tally of ca. 250,000–300,000 dead within a population of probably 500,000 would fall squarely within the most carefully derived estimates for the death rates in places hit by the Black Death at 50–60%.

Ancient societies were always tilted toward the countryside. By now some 85–90% of the population lived outside of cities. What set the plague apart from earlier pandemics was its ability to infiltrate rural areas.

Plague had another, even more insidious stratagem in the long run. An obligate human parasite like smallpox lacked an animal reservoir where it could hide between outbreaks. Plague was more patient. As the wave of the first visitation pulled back from a ravaged landscape, small tidal pools were left behind. The plague lurked in any number of rodent species. These biological weapons of the plague—the fact that it does not confer strong immunity and that it has animal reservoirs—allowed the first pandemic to stretch across two centuries and cause repeated mass mortality events.

The social order wobbled and then collapsed. Work of all kinds stopped. The retail markets were shuttered, and a strange food shortage followed. The harvest rotted in the fields. Food was scarce.

The Late Antique Little Ice Age (536 to 660 AD) climate change effects.

AD 536 was the coldest year of the last two millennia. Average summer temperatures in Europe fell instantly by up to 2.5°, a truly staggering drop. In the aftermath of the eruption in AD 539–40, temperatures plunged worldwide. In Europe, average summer temperatures fell again by up to 2.7°.

The decade of 536–545 was the coldest during this time.

Late in AD 589, torrential rains inundated Italy. The Adige flooded. The Tiber spilled its banks and crept higher than Rome’s walls. Whole regions of the city were under water. Churches collapsed, and the papal grain stores were ruined. No one remembered a flood so overwhelming. Then followed the plague again, in early AD 590.

The combination of plague and climate change sapped the strength of the empire.

The Justinian Plague effects on religion

For the first time in history, an apocalyptic mood came to permeate a large, complex society. Gregory’s sense of the approaching end was hardly his alone. The apocalyptic key transcended traditions, languages, and political boundaries in late antiquity. The plague was a last chance to turn from sin. And no sin weighed more heavily on the late antique heart than greed. Anxieties about wealth generated a perpetual moral crisis in late ancient Christianity. Earthly possessions were a trial of faith. Here the plague struck a tender nerve. The most memorable vignettes in John of Ephesus’ history of the plague linger over individuals singled out for punishment because of their greed. From one angle, the plague was God’s final, ghastly effort to pry loose our tight-gripped hold on material things.

Materially and imaginatively, the ascent of Islam would have been inconceivable without the upheavals of nature. The imminent judgment was a call to repentance.

Monotheism and eschatological warning were central to the prophet Muhammad’s religious message. “The coming judgment is in fact the second most common theme of the Quran, preceded only by the call to monotheism.” The Quran proclaims itself to be “a warning like those warnings of old: that Last Hour which is so near draws ever nearer.” “God’s is the knowledge of the hidden reality of the heavens and the earth. And so, the advent of the Last Hour will but manifest itself like the twinkling of an eye, or closer still.” The origins of Islam lie in an urgent eschatological movement, willing to spread its revelation by the sword, proclaiming the Hour to be at hand. Here, the eschatological energy of the seventh century found its most unrestrained development. It was electrifying. The message was the last element in the perfect storm. The southeastern frontier of the empire was erased almost overnight. Political lines of a thousand years were instantaneously and permanently redrawn.

Egypt and the Justinian Plague effects

The Nile valley was the most heavily engineered ecological district in the ancient world. Every year, at the inundation, its divine waters were diverted through an immense network of canals to irrigate the land. The intricate machinery of dikes, canals, pumps, and wheels was a huge symphony of human ingenuity and hard labor. The sudden disappearance of manpower in lands upriver threw the network of water control into disrepair. The controlled flow of water in the valley had been interrupted, and the downstream inhabitants in the fertile delta were overwhelmed. Remarkably, these events were replayed almost exactly in the aftermath of the medieval Black Death.

Famine effects

The twittering climate regime of late antiquity also had an intimate relationship with the pulses of epidemic mortality. Food shortage was a corollary of disease outbreak. Anomalous weather events might trigger explosive breeding of disease vectors. A devastating famine in Italy in AD 450–51 was coincident with a wave of malaria, for instance. Food crisis fanned desperate migrants in search of survival, overwhelming the normal environmental controls embedded in urban order. Food shortages forced the hungry to resort to consuming inedible or even poisonous food, all while depleting the power of their immune systems to resist infection.

A famine and pestilence swept Edessa and its hinterland. In March of AD 500, a plague of locusts destroyed the crops in the field. By April, the price of grain skyrocketed to about eight times the normal price. An alarmed populace quickly sowed a crop of millet, an insurance crop. It too faltered. People began to sell their possessions, but the bottom fell out of the market. Starving migrants poured into the city. Pestilence – very probably smallpox – followed. Imperial relief came too late. The poor “wandered through the streets, colonnades, and squares begging for a scrap of bread, but no one had any spare bread in his house.  In desperation, the poor started to boil and eat the remnants of flesh from dead carcasses. They turned to vetches and droppings from vines. “They slept in the colonnades and streets, howling night and day from the pangs of hunger.” When the December frosts arrived, the “sleep of death” laid low those exposed to the elements.

The migrants were worst affected, but by spring no one was spared. “Many of the rich died, who had not suffered from hunger.” The loss of environmental control collapsed even the buffers that subtly insulated the wealthy from the worst hazards of contagion.

During a famine that swept Syria in AD 384–85, Antioch found its streets filled with hungry refugees, who had been unable to find even grass to eat and suddenly massed in town to scavenge

Rise of Slavery

After the dislocations of the third century, the slave system experienced a brutal resurgence.

Melania the Younger, from one of the most blue-blooded lines in Rome, owned over 8,000 slaves.

Slave-ownership on Melania’s scale was rare. More consequential were the elites, late antiquity’s 1 percent, who owned “multitudes,” “herds,” “swarms,” “armies,” or simply “innumerable” slaves, both in their households and in the fields. To own a slave was a standard of minimum respectability. In the fourth century, priests, doctors, painters, prostitutes, petty military officers, actors, inn-keepers, and fig-sellers are found owning slaves. Many slaves owned slaves. All over the empire we find working peasants with households that included slaves.

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2 Responses to The fall of the roman empire from plagues and climate change

  1. Nehemiah says:

    Slavery: by the first century AD, most of the Empire’s inhabitants were already slaves. Some chattel slavery would continue into early modern times, but most chattel slaves were eventually replaced by serfs, in part due to pressure from the bishops. Eventually, it became legal to newly enslave only heathens, and since Slavs were among Europe’s last converts to the Christian faith, there was a period when many of Christendom’s slaves came from the Slavs, thus the etymology. Preindustrial states tended to be highly unequal places, yet that does not seem to have contributed to instability, contrary to the earnest wishes of equality-minded moderns. (Forget about that “NASA” study, which NASA officially disclaimed any responsibility for and whose lead author was a grad student.)

    Growing human contact had allowed local disease microbe to go transnational by c. AD 200, and these new diseases, smallpox and others, put downward pressure on the population for centuries, creating a manpower shortage. One response was to rely less on infantry stationed at the borders and more a rapidly deployable cavalry force (St. Constantine implemented this particular change) that could be dispatched to trouble spots. Perhaps the effects of these diseases were similar to their effects on the American Indians later, but there were no resistant immigrants to displace the Europeans as the more genetically vulnerable of them died off.

    The brave and beautiful Empress Theodora succumbed to the Plague of Justinian, and although Justinian himself recovered, his health was never the same. The plague might be why they could not hold on to the Western territories that the brilliant Bellisarius was in the process of successfully reconquering when the plague struck. But what I think is really interesting is that both the 6th century plague and the Black Death in the 14th century (both believed to be the bubonic plague, which sometimes goes airborne as pneumonic plague) followed shortly on the heels of a transition to a suddenly cooler climate. Here in North America, our prairie dog population (really prairie rodents) could easily become the carriers of a new plague outbreak. Indeed, from time to time an isolated case of plague occurs even today in the US. Not a forecast, just something to think about, especially during the emerging Eddy Minimum.

    Somebody really should pay attention to peak antibiotics. Antibiotic resistance is growing rapidly, and new antibiotics are not being found nearly fast enough. To make matters worse, casual antibiotic use has decimated the diversity of intestinal biomes of many, maybe most, people in developed countries, which reduces their ability to resist infectious diseases. This biome is transmitted from mother to child, so this vulnerability to infections once antibiotic resistance becomes widespread among microbes should continue for many generations. Antibiotics are not innocuous.

    Melania’s 8000 slaves certainly impresses me. My earliest patrilineal ancestor on this side of the pond, who wed in Elizabethcity, now Williamsburg, VA late in the 18th century, bequeathed 800 slaves in his will, but that looks like small potatoes next to Melania’s 8000. In a preindustrial culture, slavery makes life easier for the slaveowners, yet, from the viewpoint of the free society’s larger welfare, there are multiple problems that develop from it, but, fear not, I am not going to elaborate today. My fingers will get tired.

    The Xiongnu or Hsiungnu, known to Sanskrit scribes as the “Huna,” harassed the borders of the Middle Kingdom for many centuries. Eventually, they cease to be mentioned anymore in Chinese annals, but some of them show up in Europe as the Huns during the volkerwunderung. The Romans had to develop new military tactics for dealing with these and other mounted horse warriors. We still know what these tactics were–or at least military historians do–but luckily we still have high powered rifles so we don’t have to worry about mounted nomadic warriors anymore. The peoples who live in the plains of central Asia are a hybrid race from the merging of Mongoloid stock from the east with fair-featured European stock from the west. In ancient times, the Chinese described the Hsiungnu as big men with beards, so they may not have been fully hybridized at that time.

    Now let’s review the risk of disease outbreaks again: globalization moves both microbes and men around the world very fast. That will slow down in the post liquid fuels age, but there should still be considerable movement for some time to come.

    If bird flu ever starts spreading person to person, it could be horrendous. These microbes are constantly mutating. But I worry more about antibiotic resistance:

    Antibiotic-resistant infections are already widespread in the U.S. and across the globe.1 A 2011 national survey of infectious-disease specialists, conducted by the IDSA Emerging Infections Network, found that more than 60% of participants had seen a pan-resistant, untreatable bacterial infection within the prior year.7 Many public health organizations have described the rapid emergence of resistant bacteria as a “crisis” or “nightmare scenario” that could have “catastrophic consequences.”8 The CDC declared in 2013 that the human race is now in the “post-antibiotic era,” and in 2014, the World Health Organization (WHO) warned that the antibiotic resistance crisis is becoming dire.15 MDR bacteria have been declared a substantial threat to U.S. public health and national security by the IDSA and the Institute of Medicine, as well as the federal Interagency Task Force on Antimicrobial Resistance.1

    Among gram-positive pathogens, a global pandemic of resistant S. aureus and Enterococcus species currently poses the biggest threat.5,16 MRSA kills more Americans each year than HIV/AIDS, Parkinson’s disease, emphysema, and homicide combined.1,12 Vancomycin-resistant enterococci (VRE) and a growing number of additional pathogens are developing resistance to many common antibiotics.1 The global spread of drug resistance among common respiratory pathogens, including Streptococcus pneumoniae and Mycobacterium tuberculosis, is epidemic.16

    Gram-negative pathogens are particularly worrisome because they are becoming resistant to nearly all the antibiotic drug options available, creating situations reminiscent of the pre-antibiotic era.1,5,16

    End quote.

    Making us more vulnerable, in addition to antibiotic resistance:

    decimated gut biomes

    rising share of elderly people, who have weakened immune systems due to age

    densely packed urban settlements

    we have probably forgotten how to enforce quarantines; some people, already infected, will still be able to afford to flee rapidly while liquid fuels continue to exist, spreading the contagion rapidly

    episodes of disaster, chaos, and disorder may lead to conditions where disease organisms can spread and turn into an epidemic

    I expect malaria will make a return at some point too. One form of malaria was common in Europe and America during the little ice age, and a malaria epidemic struck northern Russia as recently as the 1920’s. That was P vivax, the least deadly of the four major strains, but it still kills plenty of people if they lack resistance (as most people indigenous to temperate zones do), especially children and the elderly, and even those who survive it suffer terribly. Almost every pure bred native of sub-Sahara Africa seems to possess the gene that prevents infection by vivax–thus deadly enough that this gene spread rapidly. One drawback though is that the gene increases risk of prostate cancer 50%, although on a peasant’s diet that is a 50% increase from an already low level. Not low, however, on a diet with lots of animal flesh or cow’s milk.

    In ancient times, an infestation by the more deadly falciparum strain forced the Romans to move their capital away from the city of Rome itself. They did not know then that they just needed to drain the swamps.

  2. Nehemiah says:

    I wrote: My earliest patrilineal ancestor on this side of the pond, who wed in Elizabethcity, now Williamsburg, VA late in the 18th century, bequeathed 800 slaves in his will, but that looks like small potatoes next to Melania’s 8000.

    Sorry, that should read “late in the 17th century.” I am colonial stock, yet these days I am not even considered a native American. Would the Brits welcome me at this late date as a native Englishman? Given my Victorian era political views, they might not even welcome me as a tourist!