Dead Zones

According to the Fertilizer Institute (yes, there is such a thing), over 185 million tons of fertilizer were used worldwide in 2008. For America alone, the figure was 54.9 million tons. The overwhelming majority of this fertilizer is produced synthetically by combining various amounts of nitrogen, phosphate and potash. (The old-fashioned method of using animal waste for fertilizer simply will not produce enough to support the enormous amount of crops we need to grow to feed the world.)

Ever wonder where all this stuff goes after it’s used? Well, some of it is absorbed by the plants it’s used on, and some of it remains in the soil the plants grow in. But the vast majority gets washed into streams and rivers by rainfall and irrigation, and from there it ultimately ends up in our oceans.

What’s the environmental impact of all this agricultural runoff? Well, it’s not good. According to the U.S. Environmental Protection Agency, over half the streams in America (55% to be exact) can no longer support aquatic life due to fertilizer runoff. Once the runoff flows into the ocean, the nitrogen and phosphorus it contains feed the growth of enormous algae “blooms.” When these algae die, they sink to the ocean bottom, where they are decomposed by bacterial action. This process consumes the oxygen in the water, starting a chain reaction that makes it impossible for the environment to support any marine life that requires oxygen. This means no fish, no shrimp, and none of the marine mammals like seals and porpoises that feed on the fish and shrimp. It’s no wonder that these oceanic areas with little or no oxygen are called “dead zones.”

The largest dead zone ever encountered was in the Gulf of Mexico in 2012—caused by runoff from the Mississippi River. However, dead zones are not only a problem in U.S. coastal waters; they are increasing in size and number all over the world. We will examine this growing problem—along with some possible solutions—in upcoming blogs.

Photo courtesy of Pixabay.