- Start with historically massive agricultural input of phosphorus and nitrogen into the Mississippi River system.
- Add occasional yearly floods that can double the input of phosphorus and nitrogen following the flood.
- Dump the Mississippi River into an algae-rich Gulf of Mexico.
- Heat the Gulf water to a tepid 70 degrees Fahrenheit (local water temperatures may vary)
- Add lots of sunlight.
- Wait for phytoplankton algae bloom to form, then die and start decomposing.
- Ta da! You’ve finished your Gulf of Mexico Dead Zone!
- If you wish increase the size of your dead zone, just increase agricultural runoff from nitrogen fertilizers. Corn farming for ethanol would be a great way to start.
The Gulf of Mexico is one of the United States’ most important fisheries, where 72% of U.S. harvested shrimp, 66% of harvested oysters, and 16% of commercial fish are harvested for U.S. markets. But in 1985, a “dead zone” largely devoid of seabed marine life like shrimp and oysters was discovered along the Louisiana coast. Scientists determined that the ultimate cause of the dead zone was algae blooms fed by human agricultural practices, especially fertilizer runoff from corn.
As I alluded to above, nitrogen and phosphorus run off fields and are deposited by air into the Mississippi River where they flow downstream into the Gulf of Mexico. There, nitrogen and phosphorus provide so many nutrients to algae that they reproduce prolifically (bloom) until the available nutrients are all exhausted. Then the algae all die, sink to the bottom, and begin to decay. And as the algae decays, its pulls dissolved oxygen out of the water around it, reducing the amount of oxygen available for other marine life to live on. And so the area under and around the algae bloom dies from suffocation.
Now, with misguided corn ethanol biofuel subsidies available from the federal government, more acreage of corn is being planted than has been planted since WWII. The problem is that corn is horribly inefficient at using nitrogen fertilizer, and commercial corn cultivation is the single largest source of nitrogen in the Mississippi River. In 1999, the USGS released a report on the Gulf of Mexico dead zone (“hypoxic region”, meaning oxygen-poor) using the latest science available at the time. The report’s Topic 3: “Flux and Sources of Nutrients in the Mississippiâ€“Atchafalaya River Basin” was a detailed examination of the types and sources of nutrients, and it found that approximately 35% of the nitrogen flowing in the Mississippi River came from two states representing only 9% of the the entire Mississippi River basin – Iowa and Illinois.
According to the National Corn Growers of America 2007 World of Corn site (latest production data is for 2006), these two states account for almost 40% of the nation’s annual production of corn, and according to AgriView, corn production is estimated to be 25% higher this year than last, or 13.3 billion bushels in 2007-2008 vs. 10.5 billion in 2006-2007. In the period measured by the USGS, 1980-1996, the average nitrogen flux was 1.3 million metric tons of nitrogen, 35% of which came from Iowa and Illinois. Over the same period, the average amount of corn grown in the US was 7.6 billion bushels, or just less than half of the estimated number of bushels for this year. If we assume that about the same proportion of nitrogen will go into the Mississippi River this year as did back then (this is my attempt to roughly account for improvements in agriculture since 1996), then the total nitrogen released this year will be approximately 2.28 million metric tons, or 1.75x the average from 1980 to 1996. And the 1980-1996 nitrogen measurements were already 30% higher than measured historical values from 30 years previously – the new values are 228% higher than historical values.
The dead zone in the Gulf of Mexico is already about 7,000 square miles, and while that’s not the largest area on record, if we continue to dump multiple megatons of excess nutrients from our cornfields into the Mississippi River, we’ll eventually kill off one of our most valuable fisheries in the process. Unfortunately, it’s likely going to come down to a tradeoff between politically expedient corn ethanol subsidies for Iowa and Illinois and the economic benefits of a viable fishery for Louisiana and Mississippi.
Thanks to Mike “Ubertramp” Pecaut for forwarding this one on.
[Crossposted: The Daedalnexus