Gulf of Mexico Dead Zone

August/September 2006
Nitrogen from fertilizer runoff causes huge dead zones in the oceans where fish and other marine life can't survive.


In the Gulf of Mexico, several miles off the Louisiana coast, lies one of the world's largest 'dead zones' ? oxygen-deprived areas devoid of all marine life. Researchers predict that this summer, the dead zone will grow to cover nearly 6,700 square miles, an area roughly half the size of Maryland, and far larger than its size in recent years of 4,800 square miles.

Worst of all, the dead zone is human-made: runoff from farms in the Midwest adds as much as 7.8 million pounds of nitrate fertilizer to the Mississippi River and its tributaries each day during peak loading periods, which then runs downriver and empties into the Gulf. As it does with plants grown on land, the nitrogen causes algae and plankton in the area to flourish, using all available oxygen in the water. The result is hypoxia, an oxygen depleted dead zone in which fish and other marine life simply cannot survive.

According to a study done by the Environmental Working Group, much of the fertilizer runoff comes from heavily subsidized farms in the Corn Belt, an area that includes Iowa, Illinois and Indiana. Corn requires the highest fertilizer input of any major crop, and about 45 percent of all commodity support payments in that area go to its production. The money typically spent on taxpayer-funded farm subsidies in the area dwarfs the amount spent on efforts to protect water quality and conservation by a ratio of more than 500 to 1.

To learn more about the dead zone, visit the Science Museum of Minnesota's interactive site, or the Mississippi River Basin Alliance.