Greenhouse warming and potential changes to the hydrologic cycle ½gure prominently in the climatechange debate, but many other direct anthropogen ic factors are today rede½ning the state of rivers, which supply around 80 percent of renewable freshwater to society. 1 Chief among these are widespread landuse change, urbanization, industrialization, and pollution, all known to stress aquatic ecosystems. The highly positive impacts of a reliable water supply on economic productivity (which requires waterworks like dams, irrigation, and interbasin transfers), means that the water cycle will increasingly be controlled by humans for decades if not centuries to Abstract: Water is an essential building block of the Earth system and a nonsubstitutable resource upon which humankind must depend. But a growing body of evidence shows that freshwater faces a pandemic array of challenges. Today we can observe a globally signi½cant but collectively unorganized approach to addressing them. Under modern water management schemes, impairment accumulates with increasing wealth but is then remedied by costly, after-the-fact technological investments. This strategy of treating symptoms rather than underlying causes is practiced widely across rich countries but leaves poor nations and many of the world's freshwater life-forms at risk. The seeds of this modern "impair-then-repair" mentality for water management were planted long ago, yet the wisdom of our "water traditions" may be ill-suited to an increasingly crowded planet. Focusing on rivers, which collectively satisfy the bulk of the world's freshwater needs, this essay explores the past, present, and possible future of human-water interactions. We conclude by presenting the impair-then-repair paradigm as a testable, global-scale hypothesis with the aim of stimulating not only systematic study of the impairment process but also the search for innovative solutions. Such an endeavor must unite and cobalance perspectives from the natural sciences and the humanities.

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Histories of ocean science have emphasized the ways that state-sponsored deep-sea expeditions ushered in a new age of oceanic understanding during the late eighteenth and early nineteenth centuries. This essay, on the other hand, examines the ways that shallow waters played host to less formal but nevertheless important efforts to create oceanic natural knowledge, often centuries earlier. By documenting the legends and experiences of people who worked on and lived by the ocean-divers, sailors, and fishermen, among others-and corroborating their stories with firsthand observation, seventeenth-and early eighteenthcentury natural historians built a nascent science of the sea. In its close focus on "sea beans" and "barnacle geese," subjects of wide conjecture and earnest curiosity, the essay shows how shallow waters welcomed new actors onto the scientific stage and decentered the geographies of knowledge production, thereby advancing contemporary knowledge of oceanic circulation as well as the taxonomies and ecologies of coastal creatures. F or more than a generation now, Atlantic history has stirred up new and powerful eddies in the history of science. Comparative, transnational approaches to the study of natural history, weather, and climate, for example, have decentered the geographies of knowledge production and introduced new historical actors onto the scientific stage. 1 Yet comparatively little