Author: Andrea Basche
The National Oceanographic and Atmospheric Administration (NOAA) released Thursday its annual forecast for the size of the Gulf of Mexico “dead zone”—an area of coastal water where low oxygen is lethal to marine life. They say we should expect an “average year.” That doesn’t sound so bad, but as we wrote last year, the dead zone average is approximately 6,000 square miles or the size of the state of Connecticut. Average is not normal.
This is especially troubling when we know that solutions exist for reducing agricultural pollution, which contributes to the dead zone. And for many years, there’s been a lot of effort dedicated to reducing the dead zone’s massive footprint.
The Dead Zone Starts on the Farm
Dead zones—also known as hypoxic zones—can occur naturally, but human activity perpetuates their presence. Hypoxia in the ocean results from low dissolved oxygen, a state that occurs when excess pollutants, such as nitrogen and phosphorus, enter bodies of water. These pollutants have various natural and man-made sources, but they are critical nutrients for plant growth and thus the active ingredients in fertilizers applied to farm fields.
The movement of water causes nitrogen to “leach” through the soil or “run off” into bodies of water, while phosphorus most commonly escapes from farm fields with sediment and soil erosion. However they get into water, these pollutants make delicious food sources for algae, which “bloom” as a result of the buffet. Dead algae sink and decompose in water, which depletes oxygen, suffocating other marine organisms.
The second largest dead zone in the world is the one predicted Thursday, in the Gulf of Mexico. The Mississippi River empties into the Gulf and many other bodies of water that run through the Corn Belt and other major agricultural regions of the U.S. feed the Mississippi.
It has been a wet spring across most of the U.S., including the Midwest and it is true that the amount of rainfall (and thus water moving through and over the soil) impacts the size of the dead zone from year to year. But so do the practices on farms and these are much more within our control than the rain.