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NOAA announces largest-ever Gulf of Mexico ‘dead zone’

  • The dead zone is primarily the result of nutrient pollution that stimulates massive blooms of algae. This algae is fed by nutrient runoff from agricultural areas in the U.S. Midwest carried down by the Mississippi River.
  • An investigation found meat production largely to blame for this nutrient runoff.
  • However, representatives with the meat industry say the report failed to consider the impact of ethanol production.
  • NOAA scientists say the dead zone is likely to continue growing if nutrient levels aren’t reduced.

Last week, scientists from the National Oceanic and Atmospheric Administration (NOAA) announced the largest-ever recorded low-oxygen “dead zone” in the Gulf of Mexico. At 22,730 square kilometers (8,776 square miles) the area is the size of the U.S. state of New Jersey.

The dead zone is primarily the result of nutrient pollution that stimulates massive blooms of algae. When this algae decomposes, oxygen levels drop below levels needed by many Gulf species to survive or develop normally; scientists refer to low-oxygen conditions as hypoxia.

“The dead zone adversely affects organisms in a number of ways,” said Robert Magnien, director of NOAA’s Center for Sponsored Coastal Ocean Research. “It reduces available habitat for fish and shrimp and reduces their food supply. Exposure to hypoxia can also directly reduce growth and reproduction.”

At 22,730 square kilometers (8,776 square miles), this year’s dead zone in the Gulf of Mexico is the largest ever measured. Image courtesy of N. Rabalais, LSU/LUMCON.

This can have knock-on effects for local economies if hypoxia kills off or changes commercially important populations.

“The fear is that if the size of the dead zone remains at its current level or increases in the future, there will likely be further reductions in the abundance of key commercial and recreational species,” Magnien told Mongabay.

A study by Duke University found shrimp grow more slowly in the dead zone. This led to a deficit in large shrimp, lower prices for small ones and consequential economic changes to the Gulf brown shrimp fishery.

Midwest ag driving Gulf dead zone

NOAA scientists are pinning the blame for the increasing size of the dead zone – indeed, its existence at all – primarily on nutrients like nitrate that are washed off agricultural fields in the Mississippi watershed. The Mississippi River carries these nutrients as far as 2,000 miles before they’re released into the Gulf of Mexico.

The U.S. Geological Survey (USGS) found about 1.15 million metric tons of nitrogen pollution was released into the Gulf of Mexico in 2016; preliminary data from May 2017 indicate pollution this year is set to eclipse that number, with levels well above the 1980-1996 baseline average.

“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 research professor Nancy Rabalais in a statement. Rabalais is a research professor at Louisiana State University (LSU) and Louisiana Universities Marine Consortium, and led the survey mission that measured the extent of the dead zone.

Scientists from Louisiana Universities Marine Consortium deploy a water sensor called a CTD sonde rosette to collect water samples to test for oxygen levels during the 2015 R/V Pelican’s shelf wide hypoxia cruise. Photo courtesy of LUMCON

In addition to creating and exacerbating the dead zone, nitrate runoff can contaminate drinking water. A 2015 Health Department report found agriculture-related nitrate pollution is a “growing chemical threat” to the drinking water of the U.S. state of Minnesota.

Meat to blame?

Much of this nitrate runoff comes from livestock manure and fertilizer applied to commodity crop fields – namely corn and soy. These crops are primarily grown to feed livestock for the U.S. meat industry, according to a new report by the NGO Might Earth that preceded the NOAA announcement.

Mighty Earth investigated the supply chains of the country’s largest meat producers, mapping industry infrastructure and overlaying them with data on water nitrate concentrations linked to fertilizer pollution, as well as grassland clearance. They found meat-processing company Tyson Foods stood out from the rest.

“Our analysis also found Tyson to be the dominant meat company in all the regions suffering the worst environmental impacts from industrial meat and feed production – from grassland clearing in Nebraska, Iowa, and Kansas, to manure and fertilizer pollution pouring into waterways from the Heartland down to the Gulf states,” the report reads.

Grain traders Archer Daniels Midland (ADM), Cargill and Bunge provide corn and soy livestock feed to Tyson. Mighty Earth’s investigation found Cargill and ADM dominate the corn and soy market in states with the highest grassland losses.

“The expansion of new fields in these areas is likely contributing to what is projected to be the biggest Dead Zone ever this year,” the report states.

Cattle graze in Minnesota, one of the U.S. states through with the Mississippi River runs. Photo from the public domain.

Cargill and Bunge did not respond to requests for comment by press time. ADM pointed to their sustainability initiatives.

“ADM creates long-term value by providing innovative, responsibly-sourced ingredients for a growing population,” ADM spokesperson Jackie Anderson said in an email. “In the U.S., we are members of Field to Market, a supply chain sustainability program in which growers, commodity traders, and food manufacturing companies work together to improve the sustainability of crops and share aggregated environmental data. In addition, ADM has an Environmental Policy which governs the operation of our facilities, requiring compliance with environmental permits, including water discharge permits.”

Tyson is one of the world’s largest food companies. In its report, Mighty Earth contends that Tyson is driving the demand for feed “without applying any known sustainability screen to its purchases.”

“The company’s market dominance means that it has standardized many of the practices and market incentives contaminating our water and destroying our landscape today,” the report states. “But it also means that Tyson has the ability to lead the transformation of America’s agriculture industry to end these harmful practices.”


Tyson and others in the industry refute Mighty Earth’s findings, saying ethanol production is a big driver of U.S. industrial corn cultivation and is largely ignored in the report.

“We don’t agree with this group’s characterization of our company but share its interest in protecting the environment,” a Tyson company representative said in an email. “That’s why we publicly disclose our environmental efforts and recently announced that we’re collaborating with the World Resources Institute to develop goals for improving our environmental footprint.  We also plan to announce our collaboration with other third-party organizations that will work with us to set additional science-based targets.”

Tyson contends the thousands of independent farmers with whom it works have formal nutrient management plans in place, and says Mighty Earth’s report fails to consider ethanol production as a major driver of commodity agriculture.

“It’s true the livestock and poultry industry is a major buyer of grain for feed, however, the report fails to note that a large percentage of corn raised in the U.S. is used for biofuel and that a significant portion is used for human consumption,” the representative said. (Read Tyson’s full statement here.)

Fertilizer is applied to a corn field in Iowa. Photo from the public domain.

In its report Mighty Earth argues the meat market is the largest single market for corn and soybeans, pointing to USDA numbers pegging 70 percent of U.S.-grown soybeans are used for animal feed. It also draws on research that found around a third of the corn used for ethanol production is subsequently sold as livestock feed.

“As the report notes, the meat industry uses 40% of the annual corn crop and over 70% of the soy crop. Biofuels uses about 30% of the annual corn crop,” Mighty Earth campaign director Lucia von Reusner told Mongabay. “The report looked at the intersection of meat producers’ infrastructure and row cropping because this nexus has never been examined, and because we know that animal feed operations rely heavily on the feed crops grown nearby. That’s why the report mapped that overlay.

“Much has been written about the social and ecological perils of growing corn for biofuels. This report did not focus on biofuels policy for a practical reason as well: federal policy is the primary driver for that industry, and is highly unlikely to change in the near term. In contrast, meat producers are the largest demand source for both corn and soy, and, if they took action today to support more sustainable farming practices, that market signal would rapidly transform US farming practices and thus water quality as well.

“Tyson and other Big Meat companies have a responsibility to drive change for the massive share of corn and soy they buy. Once they do, those best practices will be taken up by farmers everywhere, including those growing corn for biofuels. That will benefit farmers, consumers, and the drinking water and fisheries on which we all depend.”

The race to reduce

Regardless of whether meat or ethanol production is leaching more nitrate into the Mississippi watershed, the data are clear: nutrient pollution is creating a big problem in the Gulf of Mexico. And scientists worry it is getting even bigger.

“Our models show a strong correlation between the size of the dead zone and the amount of nutrient pollution entering the Gulf of Mexico during the spring,” said NOAA’s Robert Magnien “With expected increases in runoff-producing storms and increasing temperatures in the future, the size of the dead zone may well increase even if current practices remain the same.”

A number of initiatives are working to limit the growth of the dead zone, such as the interagency Mississippi River/Gulf of Mexico Hypoxia Task Force (HTF). A consortium of federal, state, and tribal members, the goal of the HTF is to shrink the dead zone through state and federal nutrient reduction strategies.

But industry participation is also crucial, according to Magnien.

“The raising of animals, along with many other human activities that produce nutrient pollution, contribute to dead zone formation,” Magnien said. “Reduction of nutrient pollution requires a multi-sector management strategy. The cooperation of industries and municipalities to significantly reduce nutrient runoff from land and wastewater will be needed not only for restoration of impacted areas of the Gulf, but also to protect drinking water supplies and freshwater lakes and reservoir in the watershed.”

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