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

The "fate of Rome" is one of the most enduring controversies in ancient history. In this book, Kyle Harper takes the debate over the causes of Roman civilizational collapse in a welcome new direction by emphasizing the environmental forces that, he argues, contributed both to the fluorescence of Rome's empire in the first century and a half of the Common Era and to its faltering and ultimate failure in subsequent centuries. Harper draws upon an impressive range of evidence, from ancient testimonies to recent paleomolecular and climatological research, to place natural climate change and its consequences (most dramatically, the pandemics that periodically swept the empire from the mid-second century ce onward) at the forefront of his narrative of the fall of the Roman Empire.

The first chapter provides an introduction to the shape and structure of Rome's Mediterranean empire at its height, as well as to the broader processes of climate change at work both within and beyond the empire. Harper divides the climatic history of the Roman Empire into three phases, the Roman Climate Optimum, the Roman Transitional Period, and the Late Antique Little Ice Age. These phases saw four decisive turns, all of which Harper argues were brought about to some extent by environmental change: the interruption of Roman economic and demographic expansion triggered by pandemic in the mid-second century, the near-collapse of the political and economic foundations of the empire in the mid-third century (the much-debated "third century crisis"), the permanent split of the western and eastern empires at the end of the fourth century, and the final reduction of the eastern Roman empire to a Byzantine rump state in the seventh century. Harper characterizes the first phase, the Roman Climate Optimum (200 bce–150 ce), as a warm, wet, and stable period throughout much of the empire that enabled unprecedented demographic and economic growth (ch. 2). It was followed by the Roman Transitional Period (150–450 ce), an era of climate disorganization in which the empire suffered its first pandemics, the Antonine Plague (most likely smallpox) and the Plague of Cyprian (chs. 3, 4). This period also saw Gothic and Hunnic mass migrations into the empire, stimulated at least in part by environmental crisis in the Eurasian steppe, that felled the western Roman state (ch.5) Yet the coup de grâce did not come until the Late Antique Little Ice Age of the mid-sixth century, a period of extreme cooling that, together with the Plague of Justinian (recently identified by dna sequencing as the bubonic plague), eventually brought about the permanent retrenchment of the eastern Roman state in the face of advancing Islamic armies (chs. 6, 7).

This book brings the insights of new research across a range of scientific fields to bear on a well-trodden historical topic in a substantive and accessible manner. In vivid and engaging prose, Harper lays out the climatological and molecular evidence that form the heart of his argument for an environmentally-centred history of Rome. Yet this is not a history devoid of human actors. Indeed, Harper interweaves environmental processes into a narrative of dramatic political, economic, and religious changes (most consequentially, the rise of Christianity and Islam). He neatly balances the insights of recent science with the voices of contemporary witnesses both famous (Galen, Procopius) and obscure (John the Almsgiver, John Moschus). A challenge to any sweeping narrative of late Roman history is the diversity of Rome's empire and the differential pace and extent of political, economic, and social change across it. Harper adeptly elucidates the broad historical processes at work in the empire as a whole, but is also attuned to regional variation, particularly as revealed by archaeological evidence.

As Harper traces Rome's long history of encounters with natural threats both local and empire-wide in scope, he emphasizes the resiliency of the Roman imperial order...