Few topics are as debated in environmental scholarship as the Anthropocene, a proposed geological epoch that draws attention to the world-altering force of human agency. Specialists in many disciplines debate when it started, critique its implicit assumption of universal culpability, and even question its existence. Yet in most circles, it is commonly understood that the Anthropocene idea is a product of modernity. It is hard to conceive of a concept more reliant on the expansive understandings of time and space that modern science provides. Yet in After the Flood, Lydia Barnett reveals that the idea has deeper roots than most suspect: roots that stretch back, she argues, into the sixteenth and seventeenth centuries. Nor did the early modern notion of an Anthropocene depend exclusively on empirical, observational science. Instead, Barnett shows, “pious natural philosophers” drew on the biblical story of the Flood to imagine human action—and, more specifically, human sin—as a force capable of “ruining the climate and planet” (2–3). Most of us fear environmental collapse in our future; early modern Europeans believed that it had already happened in their past, and that they had to live with the consequences.

Just like today's Anthropocene, Barnett claims, this was an idea with both implicit and explicit political power. Drawing on Ann Blair's notion of Mosaic natural philosophy, Barnett shows that natural philosophers studied the Flood to unite European science and religion, and thereby repair the religious schisms of the Reformation. Yet many had a more sinister purpose. By hunting for evidence of the Flood scattered around the world, Barnett reveals that scholars sought to prove that every race and civilization descended from Noah's migrating ancestors, which meant that all belonged within Christendom. And since it rendered everyone into a migrant and traced the origins of some migrants to supposedly less admirable cultures than others, the notion of a flood-degraded world stripped indigenous land claims of their legitimacy. Noah's Flood, in other words, laid the groundwork for European empire.

These are themes that resonate in part because historians have so thoroughly reimagined early modern science as deeply entwined with empire and religion. Yet Barnett does far more than cover familiar ground. She stresses repeatedly that her aim is not to revisit increasingly tedious debates about who discovered what about the global environment and its causes for change. Rather, her goal is to show both that the idea of a global environment alterable by human agency is much older than most appreciate, and that this idea has had world-shaping political consequences. It is a powerful and necessary intervention, one informed by insightful reading in everything from environmental science to cultural studies. That it all hinges on early modern interpretations of one clear story—the legend of the Flood—imbues the book with impressive focus, given the broad intellectual terrain it covers. One is reminded of Beethoven's talent for finding new variations on a simple melody.

At times Barnett pushes her argument a bit too far, although never in ways that undermine her core claims. The notion of a planet degraded by human action, for example, is not an early modern invention, as Barnett suggests, but rather an idea perhaps as old as agriculture—and certainly as old as ancient flood myths. More importantly, although Barnett seems to believe that early modern concepts of a planet degraded by human action had little relation to reality, one proposed starting date for the Anthropocene is in fact 1610. The depopulation of the western hemisphere may then have reduced atmospheric concentrations of carbon dioxide by permitting widespread afforestation. There are reasons to doubt such claims, but certainly early moderns did profoundly alter and in fact degrade environments on a global scale, both purposefully and by inadvertently unleashing Eurasian organisms in previously isolated ecosystems.

Barnett unearths connections between shifting ideas of global environments and real environmental changes. She considers, for example, how a trend toward increasing precipitation provoked local floods and stimulated fears of a global deluge in late sixteenth-century Europe. One wonders, however, whether she could have pushed the argument a bit further. Did the contemporary onset of the Little Ice Age, a period of climatic cooling and associated precipitation extremes, stimulate new thinking not only about flooding but also about environmental extremes and the potential of human agency to bring them about? These caveats aside, Barnett has crafted a critical addition to the scholarship of both early modern and modern environmental thought. Clearly, the roots of today's environmental problems and ideas run deep.