Dead Zone Pollution Is Growing Despite Decades of Work, So Who’s the Culprit?By Sara Shipley Hiles, Environmental Health News
12 July 2012
In July 2011, the Gulf of Mexico’s dead zone was about 6,800 square miles. Photo Credit: Nasa.gov
HERMANN, Mo. – The Missouri River stretches more than a quarter-mile from shore to shore here, its muddy water the color of coffee with a shot of cream.
The river carved this valley hundreds of thousands of years ago, and in the 1830s, it deposited the German settlers who founded this city. Today, visitors who sip local wine in hillside gazebos can gaze down at the water and imagine being on the Rhine.
For two centuries, Hermann has been known for the Missouri River – and now the river is making Hermann known for an unexpected reason: It is a hot spot for nitrate.
Washing off farms and yards, nitrate is largely responsible for the Gulf of Mexico’s infamous “dead zone.” Nitrate and other nutrients from the vast Mississippi River basin funnel into the Gulf, sucking oxygen out of the water and killing almost everything in their path.
The pollution is one of America’s most widespread, costly and challenging environmental problems, according to the U.S. Environmental Protection Agency. Sewage treatment plants along the rivers already have spent billions of dollars, and some farmers now use computers to apply fertilizer with pinpoint precision.
But after three decades of extensive efforts to clean it up, nitrate along the rivers is getting worse. In Hermann, the levels have increased 75 percent since 1980, according to U.S. Geological Survey research published last year.
The pollutant continues to pour into the rivers, and ultimately the Gulf, at a growing pace. And no one – at least yet – has figured out exactly why.
1,247 miles downstream
Hermann is an ideal place to start unraveling the mystery. There are no big factories here, no major sewage treatment plants, and not even much of the intensive row-crop agriculture sometimes blamed for heavy runoff. Rather, this small city looks like something out of a German fairy tale. Churches, shops and red-brick houses line tidy streets. Vineyards dot the rolling hills. Tourists arrive via Amtrak train to hear oom-pah bands at Oktoberfest and dine on bratwurst with sauerkraut.
How could Hermann be responsible for increasing the pollution that creates a dead zone 1,247 miles downstream?
The answer is Hermann is merely a microcosm of an immense problem involving 31 states and more than 76 million people.
Hermann sits roughly in the center of the vast Mississippi River basin, which drains 1.24 million square miles stretching from the Rockies to the Appalachians.
The Missouri River, as it rushes past Hermann’s churches and shops, carries the residue of life upstream. Rain washes excess nitrogen and phosphorus, along with other pollutants, from farmers’ fields, cities, factories, cars and suburban lawns into ditches, streams and tributaries, and finally to the river itself. The “Big Muddy” joins the mighty Mississippi just north of St. Louis, then makes a sharp right turn and rushes past the soaring St. Louis Arch on its way to the sea off Louisiana.
When the nutrient-rich water empties into the Gulf far downstream, it triggers a biological phenomenon with deadly results. The nutrients serve as an all-you-can-eat buffet for hungry algae. The phytoplankton population booms and then dies, sinking to the bottom, where bacteria decompose the organisms and use up precious oxygen in the process. The resulting low-oxygen environment – also called hypoxia – is so toxic that all animals must flee or die.
Hypoxia drives away shrimp, crabs and fish and kills creatures such as worms at the bottom of food chains.
“There is die-off, a loss of ecosystem diversity,” said Nancy Rabalais, a marine ecologist and director of the Louisiana Universities Marine Consortium in Chauvin, La. “If you have continuous year-after-year hypoxia, some animals won’t be able to recruit back into the area.”
Rabalais has been mapping hypoxia for almost 30 years. Her research helped spawn a state/federal task force, which set a goal of cutting the Gulf’s dead zone almost in half, to about 1,930 square miles, by 2015.
Yet the dead zone keeps growing fatter, like an obese patient unable to shed weight. Last year it was 6,800 square miles – more than triple the goal.
“We’re a long way from the target now – a very long way,” she said. “When that target was set, it didn’t seem impossible, but it’s just getting harder and harder.”
In addition to the 75 percent increase at Hermann, nitrate levels have increased 76 percent since 1980 along the upper Mississippi River at Clinton, Iowa, according to the USGS research. In all, nitrate runoff in the entire basin increased 9 percent over the past 30 years, and much of that increase came from the watershed upstream of Hermann and Clinton.
“This the first time anyone has been able to show the actual concentrations have either not changed or actually increased when we’re supposed to be reducing the loads,” said Don Scavia, a professor of environmental sustainability at the University of Michigan in Ann Arbor who studies the dead zone.
“Whatever conservation practices have been put in place are not enough,” he said.
The corn theory
One theory is that more fertilizer is washing into the watershed because corn acreage has skyrocketed. But urban runoff, livestock and other sources could play a role, too.“These are really large watersheds with a lot of things happening – changes in crop patterns, livestock use, human population,” said Lori Sprague, a USGS hydrologist based in Denver who was lead author of the nitrate study. “All of those things change water quality.”
Farm fertilizer and livestock manure are the two biggest sources of total nitrogen in the Missouri River watershed, together responsible for 70 percent, according to 2011 USGS data. A 2008 study of the entire Mississippi River watershed had similar findings, with agriculture contributing 70 percent of the nitrogen and phosphorous that ended up in the Gulf. Scientists in 2009 also reported a direct correlation between intensive crop production, particularly corn, and nitrate-nitrogen levels in rivers.
Nationally, consumption of nitrogen fertilizer has tripled since the 1960s, surging to 12.3 million tons in 2010, according to USDA data. The amount of nitrogen applied as farm fertilizer grew 18 percent between 1987 and 1997, according to a 2006 USGS study.
It sounds clear-cut. Many farmers, however, tell a different story.
In the Bootheel area of southern Missouri, farmer Mike Geske grows about 2,000 acres of corn, cotton, rice and soybeans near Matthews, Mo. The land lies flat as a plate, the northernmost reaches of the fertile Mississippi delta.
Geske, a third-generation farmer, said when he first started farming in the 1970s, he would lay a thick dose of fertilizer on his fields in the spring. “Anhydrous ammonia was so cheap, we put on 80 to100 pounds extra,” he said.
Today, he applies fertilizer three or four times throughout the year so plants can use it as they need it. He said he uses 20 to 25 percent less fertilizer these days, yet he gets 25 to 30 percent more bushels of corn per acre. He credits better seed technology and careful management of nutrients in the soil.
Farther upstream, fourth-generation farmer Ron Hardecke raises crops, hogs and cattle on 2,000 acres in Owensville, Mo., about 35 miles south of Hermann. He said he carefully monitors his nitrogen use.
“Sometimes it’s portrayed we’re out here dumping fertilizer for fun,” he said. “But if you pay the bill, why, you don’t use more than you need.”
Nationwide, farmers are getting more grain out of their fertilizer, according to the National Corn Growers Association. Nitrogen use has decreased 38 percent in terms of pounds per bushel of corn, said Rod Snyder, director of public policy for the trade group.
Nevertheless, corn farmers are using as much fertilizer per acre as ever on their high-yielding crops, according to federal data. On average, farmers applied 58 pounds of nitrogen per acre to corn crops in 1964. By 1985, that number had grown to 140 pounds per acre, where it remained in 2010.
In addition, more acreage is being planted as corn prices boom, according to U.S. Department of Agriculture data. In 2012, farmers planted 96 million acres of corn – the highest level in nearly 70 years, and up nearly 22 percent from a decade earlier.
“The primary cause