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REDUCING RUNOFF: “There’s more conservation work to do to reduce nutrient loss from the land, but we’re on the right track,” says Mike Naig, Iowa Secretary of Agriculture.

Gulf of Mexico 'dead zone' smaller this year

Iowa Secretary of Agriculture responds to NOAA’s annual Gulf of Mexico hypoxia zone survey.

Each year in early August, the National Oceanic and Atmospheric Administration (NOAA) releases its annual Gulf of Mexico hypoxia zone survey results. This year when NOAA scientists measured the hypoxia zone in late July, they found it to be 2,116 square miles — the third-smallest measurement since NOAA began surveying the “dead zone” in 1985.

The dead zone is an area of water with low to no oxygen, a situation that kills fish and marine life. This area in the Gulf of Mexico is attributable in part to agricultural runoff from 31 states, including Iowa. “Our measurement this year showed the dead zone was much smaller than expected,” says Nancy Rabalais, a professor at Louisiana State University. Her team helps NOAA measure the dead zone. “This was well below the projected estimate, which was about four times larger,” she says. “Hurricane Hanna cut the size of the dead zone this year.”

Dead zone is still a problem

The hurricane, which passed through the Gulf just days prior to the survey, mixed the Gulf’s water in that area, disrupting the hypoxic, or dead, zone. In a conference call with media when the report was released Aug. 4, Rabalais said she expects the hypoxic zone to form again within a few weeks.

Runoff from Iowa and other states contribute to the Gulf dead zone, which forms when excess nutrients drain into the Gulf from streams and rivers and stimulate algae growth during spring and summer. The algae eventually die and decompose, depleting the water of oxygen. Fish and marine life must either move or die.

Iowa’s Naig co-chairs task force

Iowa Secretary of Agriculture Mike Naig is co-chair of the Gulf of Mexico Hypoxia Task Force, a partnership among 12 states bordering the Mississippi and Ohio rivers; five federal agencies, including EPA and USDA; and the National Tribal Water Council. The task force is working to reduce point and nonpoint source nutrient pollution in the Mississippi River basin, and reduce the extent of the hypoxia zone in the Gulf of Mexico at the mouth of the Mississippi River.

In response to the 2020 NOAA annual Gulf of Mexico hypoxia zone survey, Naig notes: “The annual hypoxia zone measurement is just one indicator used to gauge our efforts to improve water quality throughout the Mississippi River basin. As co-chair of the Gulf of Mexico Hypoxia Task Force, I know that leaders from 12 states bordering the Mississippi and Ohio rivers are working alongside federal agencies to help improve water quality locally and downstream. Hypoxia zones aren’t unique to the Mississippi River. This is one of 400 hypoxia zones in coastal areas all over the world.”

The annual NOAA measurement shows significant variability in size each year. The Gulf of Mexico hypoxia zone was the largest in 2017, measuring 8,776 square miles. Just one year later, it was 2,720 square miles, the fourth-smallest since 1985. Many things influence the size of the hypoxia zone, and weather is the most influential. Not enough water, too much water and the weather affecting the Gulf, including hurricanes, can affect the size of the hypoxia zone.

Dead zone varies year to year

While the size of the zone fluctuates each year, it remains an important way to measure success in reducing nutrient loss from farmland as water drains into creeks, streams and rivers, eventually reaching the Gulf of Mexico. “Our task force is committed to improving water quality and showing continuous improvement,” Naig says. “We must find the right balance between improving water quality while maintaining productive food and transportation systems, and empowering people to enjoy economic prosperity up- and downstream.”

Each state represented on the Gulf of Mexico Hypoxia Task Force has committed funding, research and resources to implement nutrient-reduction strategies that fit local landscapes and address local needs. “We can all recognize that effectively managing storm and wastewater and adding soil and water conservation practices upstream will have positive impacts on our local streams and the size, severity and duration of the hypoxia zone in the Gulf of Mexico,” Naig says.

He adds, “This process takes time, as we’re talking about making changes on a subcontinent level, but I’m confident we are on the right track. In Iowa, we’ve decreased total point and nonpoint source phosphorus by 18.5%, after decades of work, thanks to widespread adoption of soil management practices like no-till farming, and better storm and wastewater management practices.”

Farmers are on the right track

Today, farmers in Iowa and other states bordering the Mississippi River are accelerating the adoption of cover crops and edge-of-field practices to further reduce nutrient losses, particularly for nitrogen, Naig notes. “We know there’s still work to do, but we are deploying proven, science-based strategies. And we have more funding, more private partners and more farmers engaged in conservation efforts than ever before.”

Each state has similar success stories to share. “To learn more about the conservation work happening all over the Mississippi River basin, I encourage people to reach out to my peers on the hypoxia task force,” he says. “We’re all working hard and working together to install more conservation practices on our local landscapes to improve and protect our natural resources — and yours.”

To learn more about the Gulf of Mexico Hypoxia Task Force’s conservation efforts, visit

Will Iowa’s voluntary strategy work?

The NOAA’s annual hypoxia zone determination in the Gulf of Mexico is a key measure used by the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force to measure progress toward achieving its five-year average target of 1,900 square miles or less by 2035. During the recent press conference when the 2020 NOAA hypoxia zone survey results were announced, Naig was asked if farm states such as Iowa need regulations to reduce nutrient losses. He answered by saying the goals of Iowa’s Nutrient Reduction Strategy (INRS) are “voluntary, but not optional.”

Iowa’s strategy, adopted in 2013, seeks to reduce by 45% the nitrogen and phosphorus levels coming from urban and rural areas in the state and flow down the Mississippi and Missouri rivers that contribute to the Gulf of Mexico dead zone. Iowa’s strategy requires that cities, businesses and other point sources of nitrogen and phosphorus discharge must meet nutrient reduction requirements. But nutrient losses from farms and other nonpoint sources are not regulated.

“Models are models and estimates are estimates,” Naig says. “Even this measurement of the annual size of the dead zone in the Gulf is a point in time. These are important pieces, but they don’t tell the entire story. There is more work going on up and down the river now than there has been before. Looking at Iowa, I know we have more resources, more funding, more partnerships, more conservation and more water quality work being done.”

A report on Iowa’s Nutrient Reduction Strategy released in July says conservation practices have cut phosphorus losses by an estimated 18.5% from 2006 to 2010 in the state. Nitrogen loss, however, has risen an estimated 5%. “To achieve lasting change, to create a culture of conservation rather than a culture of regulation, we work with landowners and cities and industry,” Naig says. “And we know it will take a tremendous amount of time, years of work, to accomplish our INRS goals.”

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