|The Roman Empire at its height, 117 A.D. From Huffington Post Oct. 12, 2015|
ALERT: I find this article very interesting, but also have some question about the facts, e.g., on p. 108 he refers to a "massive volcanic eruption in AD 169" for which I cannot find any documentation in the volcanology literature. In a reference (Sigl et al., Nature 523, p. 543-549, 2015, there is an "unattributed event" in AD 169.
The article begins with a description of festivites in 248 AD, the thousandth anniversary of Rome. The emperor at the time was Marcus Julius Philippus, "Philip the Arab," who hailed from the southern reaches of Syria. Harper's thesis is that these festivities hid the fact that Rome was already in decline and that, within the space of the next generation when Aurelius would be emperor, the decline was set in. Harper then comments that Gibbon's famous "Decline and Fall of the Roman Empire" of the late 18th century was written from the perspective of its time, when the role of environmental change was not thorougly explored. Data provided from ice cores, tree rings, marine deposits and cave minerals allow historians to reconstruct climate history on "civilizational time-scales with razor precision."
Accumulated evidence suggests that Romans were short in stature, the average man standing 5'5" tall. Harper takes this as a measure that the resources that contribute to human health were already stressed. Human health is a function of both genes and the environment, the environment being critical to providing nutrition. The short stature, he hypothesizes, was due to a heavy burden of infectious disease that "drained their bodies' metabolic resources and stunted their growth." The environment, in this view, contributed to ill health (he discusses, but discards, Gibbon's thesis that the problems were either endogenous or exogenous but due to the "inevitable effect of immoderate greatness," i.e., overexpansion.
Rome grew from a collection of small huts along the Tiber River rather slowly and fairly locally through many centuries until roughly the second century BC, e.g., as possibly defined by the Battle of Carthage in 149 BC. After the Romans razed Carthage, they controlled the Mediterranean, referring to it as mare nostrum, "our sea." The built an agrarian tributary empire that extended north to the 56th parallel down to the 24th parallel, from mid-latitudes to the edges of the tropics. This environment, particularly close to the Mediterranean, is a delicate and complex ecosystem, consisting of a patchwork of microclimates. The western territories are under the influence of Atlantic Ocean patterns, whereas the Eastern Mediterranean is influenced by this but also by other systems that influenced winter precipitation. Egypt, "the breadbasket of the Empire" was yet another climate regime. Movement of food over this huge area was expedited by the huge road system and control of shipping lanes in the Mediterranean. Malthus's "gigantic inevitable famine" hit the Romans only through times of relatively high prices. (Malthus, BTW, published just a decade after Gibbons.) Just as innovations in agricultural fertilization in the 20th century avoided the Malthusian consequences of soaring planetary population, trade and technological improvements forestalled limits on the productivity of land controlled by the Romans. And, just as we have been in a period of climate hospitality at present, there was a period called the "Roman climate optimum" in the late Holocene for the Mediterranean climate. Climate, commerce and technical progress allowed enormous population growth. Though, signs of stress were present in the short stature and low life expectancy (even by ancient standards). Summers were characterized by gastroenteric illnesses, autumns by malaria. "The Romans were rich, but sick."
In the 160's A.D., smallpox struck, probably brought in along the trade routes from the Red Sea.It was the so-called Antonine Plague, perhaps the world's first pandemic.The benign climate that had blessed the Empire for a long time came to an end, perhaps with the mysterious AD 169 eruption that I mentioned above, but whatever the cause, for the next few centuries the climate began a descent into the "late antique little ice age." In AD 244 and 246, the Nile waters failed to rise. The price of wheat rose, and the food crisis in Egypt was felt throughout the Empire. One purpose of the millenium AD 248 games was to "ward off the evils of pestilence." The Plague of Cyprian (a bishop of Carthage who described the disease) ravaged the empire from AD249 for about 20 years. Alexandria, where it started, lost 62% of its urban population, 5000 corpses per day were wheeled out of Rome. Barbarians, who had previously been repelled rampaged, and the Empire started dissolving.The fabled Roman coinage collapsed and inflation ran rampant until gold was brought back as coinage. Later in the late third century, a very different empire arose.
Harper concludes by pointing out that historians have mountains of new knowledge about ancient environments due to scientific advances. Earlier historians tried to explain the events of the first centuries AD without knowing the evidence about climate change and disease. "The proud urban people who cheered in the circus, or sang in the processions of the ludi saeculares in AD 248, could little have imagined that dynamic cycles in our proximate star, or the chance mutation of a virus in a far-off forest, would rattle the foundations of the familiar world they inhabited."...."an occasional and wary glimpse to the present?????
P.S. Note that there is also a literature on the role of lead poisoning, but it has become increasingly controversial, e.g., this article.