At an eye-popping price tag of $2.7 billion every year, the country could meet the national goal of reducing the dead zone in the Gulf of Mexico to 1,930 square miles, according to a new report published in the Proceedings of the National Academy of Sciences.
The dead zone — an area of low oxygen that can’t support marine life — forms every summer after nutrients from upriver activities like farming or urban runoff stimulate the growth of algae. The algae then use up oxygen as they fall to the water bottom and decompose.
The paper reports the results of a computer model that looked at the effect on water quality of various farming methods and then identified areas where the most benefit could be achieved through targeted investment in agriculture conservation practices.
“We’re trying to decide where, in the entire Mississippi River and Atchafalaya River watershed, to put these agricultural practices,” said Sergey Rabotyagov, lead author of the report and associate professor of natural resource economics in the University of Washington School of Environmental and Forest Sciences.
“The Gulf of Mexico hypoxia (dead zone) has garnered significant public and scientific attention, so we thought we should focus on this,” he said.
Conservation practices the group recommends include methods like planting vegetation around agricultural fields to help absorb fertilizer runoff or building terraces to slow down water flow from fields, as well as to capture nutrients and sediment before they get into streams.
There also are ideas such as changing the time of year when fertilizer is applied to agricultural fields.
The computer modeling used by the team of 12 researchers found that focusing conservation funding on 68,726 square miles of agricultural land primarily in the Midwest would bring the size of the dead zone down to the national goal.
But that work would take an estimated $2.7 billion annual investment, a figure that is exceedingly ambitious.
“That’s the upper limit,” said Eugene Turner, a professor in the LSU School of the Coast and Environment and one of the report’s authors.
A number of conservation practices, like the use of a cover crop to keep nutrients in place, weren’t included in the modeling and could help bring the cost down.
Fellow author Nancy Rabalais, executive director of the Louisiana Universities Marine Consortium, was hopeful the price tag wouldn’t end up quite so expensive. “I think these methods will become more cost-effective,” she said.
Other possibilities could be a national shift away from being so heavily dependent on corn production and encouraging farmers to move to other perennial crops that would better hold soil and nutrients in place, she said.
“The social aspects are the hardest to overcome,” she said.
In addition, the report’s investment figure doesn’t take into account the additional benefits of tackling the dead zone, such as improving water quality in general, Turner said. Also, farmers would see reduced costs since fertilizer would stay on their fields and not have to be reapplied as often.
“The net benefits would be much, much better,” Turner said.
The dead zone measured 5,052 square miles this year during the annual survey cruise done by scientists at the Louisiana Universities Marine Consortium.
Although this was smaller than the 5,840 square miles measured in 2013, it’s still much larger than the goal of 1,930 square miles.
The largest dead zone recorded was 8,481 square miles in 2002; the smallest was measured in 1988 — 15 square miles, primarily because of drought conditions.
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