Chemical runoff from Midwest farm fields is contributing to the largest so-called dead zone on record in the Gulf of Mexico.
Scientists have mapped the size of the oxygen-deprived region in the Gulf since 1985. This year’s is estimated at more than 8,700 square miles, which is about the size of New Jersey.
The amount and timing of rainfall contribute to the washing of chemicals from farm fields throughout the watershed into the Mississippi River and down to the Gulf.
Robert Magnien, an oceanographer with the National Oceanic and Atmospheric Administration, says flows of nutrients this year were greater than normal.
“So in years like this with a lot of precipitation and higher than normal flows,” Magnien says, “that carries more nutrients into the Gulf of Mexico to fuel the algal bloom, which eventually decompose and rob the water of oxygen.”
The resulting hypoxic region has biological and economic implications for the region, such as certain fish being deprived of their primary food sources and potentially smaller shrimp available for market. But Magnien says in recent years the problem has gained much more attention, which he’s hopeful will translate to better nutrient management in the future.
“We’re over the hump in terms of what the problem is and what needs to be done,” he says, “and now we’re on to the really difficult job of reducing sources from, especially land runoff.”
Magnien says some solutions are available and need to be more widely adopted, such as precise use of nitrogen and wider adoption of cover crops that keep nutrients on the land.
“And, possibly, new technologies that will help with precision application of nutrients and prevention of runoff events,” he says.
The measurement is a blow to groups - from farmers to regulators to environmentalists - that hoped their ongoing efforts throughout the watershed would reduce the size of the dead zone.