The Fate of Rome: Climate, Disease, and the End of an Empire by Kyle Harper (review)

For centuries, few topics have inspired and frustrated historians like the decline, dissolution, and final collapse of the Roman Empire. Yet all along, Kyle Harper argues in The Fate of Rome, scholars have ignored the great natural forces that made it all possible. To Harper, a torrent of new evidence from so-called “natural archives”—the vast storehouses embedded in ice cores, tree rings, or genetic material—has suddenly revealed what really doomed the Romans.

The Empire, it turns out, depended all along on a mild, wet climate and a benign disease ecology. The average temperatures and circulation of the “Roman Climate Optimum” usually fostered rich harvests along the Mediterranean as the Roman Republic expanded and became an empire. Outbreaks of epidemic disease, meanwhile, never caused more than local disturbance. For a while, Harper argues, “the Romans were, in planetary perspective, lucky” (p. 14).

Yet, the Romans had unwittingly crafted an empire that sickened its urban-ites and teetered perilously close to the demographic and agricultural limits of an anomalous climate. When environmental conditions soured, the Romans were exposed. In the 160s and 170s, Harper explains, smallpox swept along the trade routes of the Empire, claiming millions of lives. The Empire could not fully recover, but it survived, in weakened form. Then, midway through the third century, another pandemic—possibly influenza, more probably a hemorrhagic fever—exacted a similar death toll just as the Sun’s activity declined and the Mediterranean climate therefore cooled and dried. With so many dead and grain increasingly scarce, the Empire came apart.

Somehow, it forged itself anew—as a different kind of Empire—in the fourth century, as epidemics stayed at bay and the Mediterranean climate warmed again, albeit erratically. The mild but volatile climate of the fourth century, however, also brought suffocating drought to the Eurasian steppe, spurring the migration of nomadic peoples to the west. “Armed climate refugees on horseback” (p. 192), Harper writes, eventually broke the back of the Empire, and permanently ended its presence in the West. Finally, in the sixth century, the calamitous arrival of bubonic plague amid the sudden cooling of the “Late Antique Little Ice Age” killed half the population of the eastern Roman Empire, and ended any effort at restoring what had been lost. Victim to a merciless environment, the Roman Empire had fallen.

This is an elegant story, and The Fate of Rome is indeed a beautiful book, clearly the product of fruitful collaboration between a gifted author and a devoted publisher. It is powerfully argued and skillfully organized, enlivened throughout with first-hand accounts that add poignancy to the many catastrophes it chronicles.

Harper has a rare knack for engaging a reader while explaining—with impressive accuracy—the complex mechanisms behind climatic shocks and epidemic outbreaks. In a typical turn of phrase he writes, for example, that “the smiling days of the Roman Climate Optimum came tripping to an end in the later second century” (p. 131), and that “the fourth century climate . . . was favorable but fluttering” (p. 170), indeed “twittering” (p. 174). We learn that the North Atlantic Oscillation—an atmospheric mode that often defies easy explanation—is “like a global-scale yard sprinkler [spraying] storm tracks over the middle latitudes of the northern hemisphere” (p. 168). And, we share Harper’s “tingling drop of wonder” (p. 202) at the horrific destruction wrought by Yersinia pestis, the sinister pathogen behind the bubonic plague. Climate history and disease history—two offshoots of environmental history—can make for painfully dry reading, as authors carefully unpack one scientific concept after another before applying them to the human past. The Fate of Rome is a striking exception.

Most histories of climate change and disease focus on disaster, and many of the best concentrate on areas of societal “vulnerability” to environmental challenges. Harper gracefully emphasizes Roman vulnerabilities while also devoting considerable attention to...