America's hugely productive food system is one of its success stories. The nation will export a projected $139.5 billion in agricultural products this fiscal year alone. It's an industry that supports "more than 1 million jobs," according to Agriculture Secretary Tom Vilsack.
But all that productivity has taken a toll on the environment, especially rivers and lakes: Agriculture is the nation's leading cause of impaired water quality, according to the U.S. Environmental Protection Agency.
Eleven miles northeast of Centralia, Mo., five U.S. Geological Survey scientists don waders and bright reflective life jackets to wade into Goodwater Creek. Plenty of fish live in the stream’s murky slow-moving waters, along with snakes, crayfish, mussels and snapping turtles. On this overcast morning, the team collects water samples and checks submerged cages of fathead minnows for eggs.