Wetland reclamation, a form of agricultural expansion and intensification, appeared in estuarine environments of northwestern Europe during medieval demographic expansion, prior to the Black Death. It included sea walls, oneway sluice gates, drainage canals, and fields reclaimed from salt marsh. French settlers introduced estuarine reclamation to Atlantic Canada (Acadia) during the early 1600s. This article examines its readaptation in Nova Scotia. Then, for the first time, it traces the roots of this sophisticated technology back to Atlantic Europe, examining reclamation and the changing role of government in France and the Netherlands. A surge of reclamation towards 1600 reflected a new political ecology, with top-down management and intervention in response to strong economic growth. Medieval reclamation technologies in Atlantic Europe differed mainly in terms of competition or collaboration between communities, church institutions, or the aristocracy. That changed after 1600 as power became centralized and new methods and lifeways were enforced from above. This unequal contestation provoked resistance, resignation, or flight. Whereas the technology implemented in Acadia was grounded in medieval practice, few of the founding settlers came from marsh areas, drawing attention to a single possible "prime mover" who directed reclamation in the style of other professional dikemasters of the era. Didactic in purpose, the study examines changing technologies and the role of institutional structures over time and draws attention to the need for a political ecological perspective in historical diffusion studies. It concludes with a synopsis of recent research on reclamation technologies of the Guinea coast and colonial South Carolina, thereby illustrating how material culture can become part of a counternarrative in settings of sociocultural contestation.