Subsidies Spur Crops on Fragile Habitat

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The ducks arrive in early April, zeroing in on thousands of shallow ponds fed by melting snow amid a vast prairie. As the pintails, mallards and blue-winged teal make nests in the grass and feed their young on abundant aquatic insects and freshwater shrimp, a 276,000-square-mile area reaching across five states and into Canada is transformed into one of the world's greatest habitats for migrating birds. Now this swath, known as the Prairie Pothole Region because of the depressions formed long ago by retreating glaciers, is threatened by the steady advance of farming. Spurred by federal subsidies and two years of surging commodity prices, farmers increasingly are digging up the grass to plant crops, raising concerns among cattle ranchers, hunters and environmental groups about the future of land where Sioux hunters chased grazing buffalo a mere century and a half ago. Today, signs of change are clearly visible. Emerald fields of ripening crops stand out against a sea of tawny grass in which a single square yard can hold 100 plant species. Rock piles tell the tale of fields cleared to make way for corn, soybeans, sunflowers or wheat. Whether U.S. taxpayers should be underwriting these changes has emerged as a controversial issue in farm country and in Washington....