Floods may yield record Gulf ‘dead zone’

June 26, 2008

Scientists predict floodwaters that decimated river cities in the Midwest also will whack the Gulf of Mexico, pushing the so-called dead zone to a record size.

Researchers from Louisiana State University and the Louisiana Universities Marine Consortium forecast the dead zone – an area that during summer doesn’t have enough oxygen at depth to support marine life – will cover 10,084 square miles, an area about the size of Massachusetts.

The expected growth in the zone renews debate over soil conservation in the nation’s breadbasket and whether farmers adding corn acres for the ethanol industry is a significant contributing factor.

Researchers such as Eugene Turner of LSU blame farmers and the ethanol industry, but an official of the Iowa Farm Bureau Federation disputes that contention, adding that corn acres are down in Iowa this year.

Since 1990, the dead zone off the coasts of Louisiana and Texas has averaged a shade over 6,000 square miles, depending largely on the flow of the Mississippi River. The area of low oxygen, or hypoxia, is caused by a large algae bloom fed by nitrogen and phosphorus from crop fertilizers, dead plants, lawn chemicals and sewage that run down the Mississippi.

When the algae die, they consume oxygen. That disrupts one of the world’s most lucrative shrimp fisheries.

The flow in the Mississippi is up 75 percent from last year. Researchers expect nitrogen levels of water running into the Gulf will be 37 percent higher than last year, the highest on record. The forecast is based on nitrate measurements in the Mississippi at Baton Rouge.

"The intensive farming of more land, including crops used for biofuels, has definitely contributed to this high nitrogen loading," Turner said. "The prediction of a large hypoxic zone this summer is because the nitrate loading this May, a critical month influencing the size, was exceptionally high."

Rick Robinson, who follows the issue for the Iowa Farm Bureau Federation, said corn acres are down this year in Iowa, and he doesn’t buy the argument that growing corn for ethanol is worsening the dead zone. "That is a politically expedient statement to make, but it’s not based on scientific fact," he said.

Robinson said high water is washing nitrogen and phosphorus from many sources, some of them natural, down the Mississippi River. He said it’s too early to tell if the dead zone will set a record this year, especially when the models don’t take into account oxygen that could be added to the Gulf when tropical storms and hurricanes come through. In the flood year of 1993, for example, storms held the dead zone to a smaller size than it was in 2002, another high-water year that brought the record dead zone.

Nancy Rabalais of the Louisiana Universities Marine Consortium expects the dead zone to be 17 percent to 21 percent bigger than the 2002 record.

Scientists plan to map the entire area July 21-29, when predictions will be checked.

The prospect of a bigger zone means that Iowa should build on its efforts – strengthened by a new state watershed council – to prioritize soil and water conservation work, Robinson said.

Wetlands and buffer strips, financed largely through federal programs and by farmers, cut pollution running to the Gulf. They can also clean Iowa’s waterways and help reduce floods in Iowa.

A federal task force has set a goal of cutting 45 percent of the nitrogen and phosphorus headed to the Gulf. Iowa Agriculture Secretary Bill Northey said that goal is lofty and perhaps unachievable.

"Those are big numbers," he said. Scientists are studying the Cedar River valley to see what it would take to achieve the goal, he added.

While farmers are nervous about what they may be asked to do, Northey agreed with Robinson that using federal programs, which pay part of the cost of conservation work, may be the best way to help both Iowa and the Gulf.