A contemporary German who visited his country in 1750, Blackbourn writes, would not recognize much of the scenery: modern fields and farms were marshland, and even the rivers, speckled with sandbars and islands, would have flowed in different courses. Blackbourn explains the social and scientific ideas behind the impressive schemes that "rationalized" the German environment, provides lively portraits of the engineers and politicians involved, and traces the sometimes unintended consequences. The nineteenth-century "rectification" of the Rhine (the work on one stretch between Basel and Worms shortened the length of the river by a quarter and removed more than two thousand islands) reduced flooding and increased arable land, but it also destroyed populations of shad and salmon. Blackbourn argues that the "conquest of nature" has been "all too closely linked to the conquest of others"; the Nazi plan to "reclaim" the Pripet marshes, in Poland, was tied to an image of their Slavic inhabitants as primitive "swamp-dwellers."