Children play on a Nigerian oil-flow station in 2007. Nigeria, a major oil source for the United States, is riddled with ancient pipes and constant spills. That, plus the geopolitical challenges involved, is why much of Nigeria's crude is the kind of "tough oil" that author Michael Klare describes. George Osodi/AP hide caption

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Plaquemines Parish coastal zone director P.J. Hahn lifts an oil-covered pelican, which was stuck in oil at Queen Bess Island in Barataria Bay, just off the Gulf of Mexico, in early June. Gerald Herbert/AP Photo hide caption

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Oil stains the rocks along a beach in Port Fourchon, La. Jeff Brady/NPR hide caption

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Efforts to clean the beach in Elmer's Island, La., were stopped Tuesday due to bad weather created by Tropical Storm Alex. Joe Raedle/Getty Images hide caption

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The looming storm could postpone BP's plans to double the amount of oil they capture from the spill. Here, a boat uses a boom and absorbent material to soak up oil on the surface of the water near Grand Isle, La., on Monday. Joe Raedle/Getty Images hide caption

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Cleanup workers maneuver an oil boom in Bataria Bay on the coast of Louisiana. With the down economy, their are plenty of people hoping for cleanup jobs, but there are few to be found. Patrick Semansky/AP hide caption

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At the midway point of the Appalachian Trail, most hikers stop in Harpers Ferry, W.Va., to have their photographs taken at the offices of the Appalachian Trail Conservancy, which administers the trail for the National Park Service. Brad Horn/NPR hide caption

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Oil-soaked booms sit on top of a marsh in Barataria Bay. Brian Naylor/NPR hide caption

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The Gulf oil spill has prompted a lot of soul-searching. Michael Spooneybarger/AP hide caption

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