WASHINGTON, Aug. 2, 2017 - The “dead zone” in the Gulf of Mexico is bigger than it’s ever been, the National Oceanic and Atmospheric Administration said today.
“Nutrient pollution, primarily from agriculture and developed land runoff in the Mississippi River watershed, is continuing to affect the nation’s coastal resources and habitats in the Gulf,” NOAA said in announcing its estimate of 8,776 square miles, which is 7 percent larger than its June forecast of 8,185 square miles.
The latest estimate – which makes the zone about the size of New Jersey – is the largest since measurements began in 1985.
NOAA says a “dead zone” is the “more common term for hypoxia, which refers to a reduced level of oxygen in the water” that can kill marine life or force it move to other areas. A study released in February showed that shrimp seeking oxygen gather on the outer edges of the dead zone, where they are caught before they have a chance to grow to full size, resulting in “shrimpier shrimp.”
The announcement is another reminder of the large role agriculture plays in debates over environmental protection – and in discussions over water quality, in particular.
This year, spring flooding in the Midwest swept nitrogen and phosphorus from fields into waterways feeding the Mississippi and thence to the Gulf.
“We expected one of the largest zones ever recorded because the Mississippi River discharge levels, and the May data indicated a high delivery of nutrients during this critical month which stimulates the mid-summer dead zone,” said Nancy Rabalais, research professor at LSU and Louisiana Universities Marine Consortium, who led a survey mission the last week of July that measured the size of the hypoxic zone.
To put it a bit more simply, “This is a weather story,” said Don Parrish, senior director of regulatory relations at the American Farm Bureau Federation. Heavy rains this spring that caused flooding from the upper Midwest down to Arkansas were beyond the farmer’s control and “overwhelmed the system,” he said.
By contrast, Midwest drought in 2012 contributed heavily to that year’s estimate of 2,889 square miles.
“Farmers are not willy-nilly overapplying nutrients,” he added. “They’re too expensive.” Instead, he said they’re using precision agriculture, nutrient loss-reduction strategies, and employing the “4 R’s” – “right source, right rate, right time, right place” – to maximize efficiency.
“They’re looking at every way possible to optimize the money they spend,” he said. But “you can’t turn rain on and off at the farm gate.”
The latest estimate comes on the heels of a study published in the Proceedings of National Academy of Sciences that says in order to shrink the dead zone to 1,950 square miles – the goal of the Gulf Hypoxia Action Plan – nitrogen runoff that flows down the Mississippi River from as far away as the Corn Belt will have to be cut by 59 percent. The federal-state task force that developed the plan originally sought to achieve the goal by 2015, but in late 2014, extended the timeline 20 years.
"The bottom line is that we will never reach the action plan's goal of 1,950 square miles until more serious actions are taken to reduce the loss of Midwest fertilizers into the Mississippi River system," said University of Michigan aquatic ecologist Don Scavia, lead author of the PNAS paper.
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