This year will be different. Heavy rainfall in the Midwest this spring has led to flood conditions, with states like Minnesota and Illinois experiencing some of the wettest spring seasons on record. And all that flooding means a lot more nitrogen-based fertilizer running off into the Gulf. According to an annual estimate from National Oceanic and Atmospheric Administration, this year’s dead zone could be as large as 8,561 sq. miles—roughly the size of New Jersey. That would make it the biggest dead zone on record. And even the low end of the estimate would place this year among the top 10 biggest dead zones on record. Barring an unlikely change in the weather, much of the Gulf of Mexico could become an aquatic desert.
The nitrogen nutrients that flow into the Gulf, especially during the rainy spring season, encourages the growth of explosive algal blooms, which feed on the nitrogen. Eventually those algae die and sink to the bottom, and bacteria there get to work decomposing the organic matter. The bacteria consume oxygen in the water as they do, resulting in low-oxygen or oxygen-free regions in the bottom and near-bottom waters.
That’s what a dead zone—water, essentially, without air. Sealife—including the valuable shellfish popular in Gulf fisheries—either flee the area, much as you or I would if someone were to suck all the oxygen out of the room, or die. That’s why the dead zone matters—the larger it is, the greater the populations of fish that might be affected. With commercial fisheries in the Gulf worth $629 million as of 2009—and still recovering from the impact of the 2010 oil spill—the dead zone means business.
The major factor driving the size of the dead zone—beyond changing flooding patterns—is the use and overuse of fertilizers in the corn belt. It takes about 195 pounds of fertilizer to grow an acre of corn; 40% of the corn crop is used to make ethanol, which is blended with gasoline. The idea is that it is a cleaner way to run our cars.
Here's the weekend reading list: