The 'Dead Zone' measures about 5,000 Square Miles (13,000 Square Kilometer) is caused by excess nutrient runoff from farms along the Mississippi River, which empties into the Gulf
The excess nutrients feed algae growth, which consumes oxygen when it works its way to the Gulf bottom
The Gulf dead zone, which fluctuates in size but measured 5,052 square miles this summer, is exceeded only by a similar zone in the Baltic Sea around Finland. The number of dead zones worldwide currently totals more than 550 and has been increasing for decades
The elongated Gulf zone typically hugs the Louisiana coastline from the Mississippi River Delta to the state's border with Texas, and some years extending offshore of Texas and Mississippi. Scientists said a growth in farmed land along the Mississippi River in the 1960s began increasing pollution. In the 1970s, levels of oxygen in parts of the Gulf fell below the needs of bottom-dwelling fish. The zone has been generally growing ever since
The report said federal farm policy impacts the amount of pollution in the river. Corn fields, which lay bare most of the year and leach nutrients, are one of the biggest contributors to the problem"
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