by Jeff Casto

Created on: September 10, 2010

The United States is known as the world’s food basket. U.S. farmers are proud of the fact that one U.S. farmer grows enough to feed 119 people yearly. This admirable feat is not without consequences, though. Fertilizers and chemicals used on farm fields in the Central U.S. eventually make their way into rivers and streams which ultimately flow into the Gulf of Mexico.

Nitrogen and phosphorus, two of the most important substances from this field runoff, act as nutrients for algae. When washed into the Gulf, these excess nutrients promote excessive algal growth, or “algae blooms.” These blooms reach a point where they need more oxygen than is available. When the algae die and fall to the bottom, the bacteria that decompose these organisms consume even more oxygen. The more algae that die, the more oxygen the bacteria consume leading to large areas of oxygen depleted water. Fish and wildlife that are able leave the area. Marine organisms that are not mobile simply die. This is the “dead zone,” an area of the Gulf of Mexico so oxygen depleted that almost nothing can live there.

The dead zone peaks in size each summer and varies each year, but grew to 8,000 square miles in 2008. In 2010, researchers measured it at 7,700 square miles, but were not able to survey the entire zone due to bad weather.

The impact of the dead zone is not just environmental. The seafood industry is highly dependent on fishing in the Gulf. According to the Journal of Food Distribution Research, some 80 percent of domestically consumed shrimp is from the Gulf. When the dead zone is large, fishermen have to travel further out to sea and burn more fuel to catch fish, shrimp, and crabs. In addition, their catch is often only 25 or 30 percent of normal. This economic impact ripples through the entire Gulf community and beyond.

Water from more than half of the United States flows into the Mississippi River. It is the main source of the harmful runoff in the Gulf. However, agriculture in six only states, Minnesota, Iowa, Missouri, Wisconsin, Illinois and Indiana, is responsible for about half of the nitrogen that flows into the Gulf. Because of this, proponents of organic farming believe it’s the best way to reduce runoff. Others are researching ways to decrease runoff from traditional farms or find ways to use less fertilizer without decreasing production efficiency.

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