IN 1973, Windell Curole was shrimping in the Gulf of Mexico with his father near the mouth of the Atchafalaya River, a distributary of the Mississippi. The river meets the salt water of the Gulf here to produce what has historically been the best shrimping grounds in the nation. After trawling for three hours, they hauled in their nets. “We came up with nothing,” Mr Curole remembers.
What the Curoles had stumbled on is now known as the dead zone, a great swathe of Gulf waters that is completely devoid of life to about ten feet below the water's surface. Each spring, when algae bloom, they are poisoned by nitrogen and phosphorous that has been washed down by the Mississippi. The algae sink to the bottom where they are decomposed by bacteria. The bacteria use up the oxygen around them. Shrimp and fish and other mobile forms of aquatic life swim off in search of oxygen; the rest dies. The condition is called hypoxia.
The dead zone is yet another setback for Louisiana's beleaguered shrimpers and fishermen. Many have little understanding of the dead zone, beyond the empty nets they are pulling up, and having to travel further to find shrimp and fish. This summer, the dead zone expanded to some 8,500 square miles (22,000 square kilometres), an area the size of New Jersey.
Most scientists agree that run-off from mid-western farms is the main cause. Nitrogen fertiliser is relatively cheap, and farmers apply it liberally. The excess nitrogen runs off into the Mississippi. According to the Environmental Protection Agency, run-off accounts for 90% of the nitrates entering the Gulf: it also reckons that 56% of those nitrates flow into the Mississippi above the Ohio River.
Many farmers in the mid-west are aware of the problems they are causing. But they say they are trapped in a system which encourages the production of corn to the exclusion of other crops, which need less fertiliser. John Conzemius, a 69-year-old farmer, tends 160 acres of crops, including corn, in southern Minnesota, 12 miles from the Mississippi. Mr Conzemius says he would rather plant alfalfa, which can soak up nitrogen much better than corn. But no federal subsidies exist for alfalfa, so he plants corn instead.
Yet more farm-subsidies hardly seem a satisfactory answer. Another obvious solution—using less nitrogen—is opposed by farmers, because it would decrease yields. Some scientists think that the nitrogen could be reduced by planting grasses to absorb the stuff before it leaves the farm. Another lot of proposed solutions involve tampering with the Mississippi itself.
The government has long attempted to control the river by means of a vast system of levees. Nancy Rabalais of the Louisiana University Marine Consortium estimates that more diversions could reduce nutrient levels in the Mississippi by 5%. Unfortunately, such tinkering has dire environmental consequences of its own, such as increasing the magnitude of flooding, degrading wetlands and destroying wildlife habitats which might well offset any potential benefits to the dead zone.
Regulations are another option. Under the Clinton administration, a White House task-force drafted an action plan meant to reduce the size of the dead zone by 30% by 2015. The task-force, whose plan sets targets for reducing nitrogen run-off and also for restoring wetlands, continues to work under the Bush administration. For now, the plan remains voluntary. But if the dead zone continues to grow, the government could choose to make it law.
Shrimpers and farmers alike hope to come up with a solution themselves. To that end, a group called the Mississippi River Basin Alliance, along with the Corn Growers Association, brought shrimpers and fishermen together for a series of meetings in Louisiana and Minnesota in 1999. Shrimpers visited farms and farmers visited shrimp boats. “The farmers and the fishermen found out that their lives are parallel,” says the alliance's director, Tim Sullivan. Their professions are equally disaster-prone and at the mercy of similar global economic forces. Perhaps that mutual understanding will help bring life back to the dead zone.
This article appeared in the United States section of the print edition under the headline "The dead zone"