The Fate of Rome: Climate, Disease & the End of an Empire
Kyle Harper
Princeton University Press
440pp, 25 black-and-white illustrations and 26 maps
Hardback, £27.95/$35.00

Historians have adduced more than 200 explanations for the fall of the Western Roman Empire. The avenues of approach have changed according to the intellectual climate of the day. The anticlericalism of Gibbon led to the dismal race theories of the 19th century. While we contend with the post-2008 economy, some of the most
interesting recent work on the fall of the Roman Empire examines weaknesses in imperial finance.

Kyle Harper, a professor at the University of Oklahoma, here takes another contemporary approach. Rome, he writes, is 'a mirror and a measure' of our age. Using fresh scientific evidence, he supplies an environmental history of the decline and fall, by tracing two intertwined factors, familiar to us from the news: climate change and pandemics of disease. The fate of Rome, he argues, was not just decided by 'emperors and barbarians, senators and generals, soldiers and slaves'. It was equally determined by 'bacteria and viruses, volcanoes and solar cycles'.

The Romans built an 'interconnected, urbanised empire on the fringe of the tropics'. Their empire prospered through a 'charmed cycle' of 'economic and demographic increase', and a consensual balance between the metropolis and its cities. If population was rising, then taxes could be kept low, and the army could be paid. If population fell, then taxes had to rise. Soldiers would be harder to find, and so would the money to pay them. This 'favourable equilibrium', Harper argues, rested on ignorance, quite understandable but nevertheless fatal, of the environmental context.

The Romans established their empire at the end of the climatic epoch known as the Holocene Era, 'in a moment suspended on the edge of tremendous natural climate change'. Though they claimed to have tamed nature through a rite at the heart of their culture, the staged animal hunt, their empire set in train the opposite process. In an 'unintended conspiracy with nature', the Romans had created 'a disease ecology, which unleashed the latent power of pathogen evolution'.

Gibbon thought that the period in which 'the condition of the human race was most happy and prosperous' was that between the death of Domitian (AD 96) and the accession of Commodus (AD 180). But this, Harper shows, was when the Roman Empire started to reach 'the very limits of what was possible in the organic conditions of a pre-modern society'. Towards the end of that period, in the reign of Marcus Aurelius (AD 161–80), economic and demographic growth were interrupted by the epidemic known as Antonine Plague. In a skilled piece of historical and veterinary detective work, Harper analyses the plague as smallpox, and traces it to the Naked-Sole Gerbil which, like many of Rome's luxury imports and some of its wheat, came from Africa.

The empire recovered from the Antonine Plague, but disintegrated in the 3rd century AD through a 'concatenation of drought, pestilence and political challenge'.

Rebuilt, the empire surged forward with a new capital and a new religion, but migratory pressures from the Eurasian steppe, themselves reflecting environmental changes, caused the collapse of the Western Empire. The Eastern Empire enjoyed rising power and population, but at the end of the 4th century AD it was struck by 'one of the worst environmental catastrophes in recorded history – the double blow of bubonic plague and a little ice age'. The resulting demographic shock played out as a 'slow-motion failure', culminating in loss of territory to the armies of Islam.

Deeply learned and clearly written, The Fate of Rome synthesises scientific research and ancient sources to advance a thesis with profound implications for our understanding of the causes of Roman decline.
Dominic Green