Record-setting rains have left Midwest cropland bogged down with so much water that many farmers have been forced to delay planting. Typically, 96% of U.S. corn crops are already planted come June,1 but in 2019 only 67% were planted as of early June — and in some states, like Indiana and Illinois, rates were as low as 31% and 45%, respectively.2
The implications of the deluge of rain, and resulting flooding, spread far beyond the agricultural fields themselves, however. There are 18 major river basins3 in the continental U.S., with the largest belonging to rivers that feed the Mississippi river.4 What is upstream will travel downstream, and this includes runoff from agricultural lands.
Pollution in the form of agricultural runoff has been linked to an excess of nutrients in waterways that leads to algae overgrowth, depleting the water of oxygen and killing fish and other marine life in expansive dead zones.
Rains may lead to ‘very large’ dead zone in Gulf of Mexico
With the high levels of spring and summer rains seen in many parts of the Midwest, scientists are predicting that the dead zone in the Gulf of Mexico will be close in size to the record-setting 8,776 square-mile dead zone measured in 2017.
The National Oceanic and Atmospheric Administration (NOAA) estimated that the summer 2019 dead zone in the Gulf of Mexico will reach roughly 7,829 miles, which is about the size of the state of Massachusetts, and bigger than the 5,770 square-mile five-year average size.5 According to NOAA:6
“A major factor contributing to the large dead zone this year is the abnormally high amount of spring rainfall in many parts of the Mississippi River watershed, which led to record high river flows and much larger nutrient loading to the Gulf of Mexico. This past May, discharge in the Mississippi and Atchafalaya rivers was about 67% above the long-term average between 1980 and 2018.
USGS [U.S. Geological Survey] estimates that this larger-than average river discharge carried 156,000 metric tons of nitrate and 25,300 metric tons of phosphorus into the Gulf of Mexico in May alone. These nitrate loads were about 18% above the long-term average, and phosphorus loads were about 49% above the long-term average.”
According to the U.S. Environmental Protection Agency (EPA), manure from industrial agriculture is the primary source of nitrogen and phosphorus in surface waterways and groundwater.7 However, runoff from chemical fertilizers spread on agricultural fields also contributes.
In dead zones, animals in the area can suffocate and die, with those unable to easily swim away, such as burrowing crabs and worms in the sediment, being most affected. Other species, like shrimp and eels, may be forced to swim to shallower waters to find oxygen.8
In hypoxic marine areas, or waters with low or depleted oxygen levels (defined in the U.S. as dissolved oxygen equal or less than 2 mg/L, or parts per million (ppm)9), widespread die-offs of fish and shellfish, along with slowed and stunted growth, is common.10
In economic terms, trends in the prices of brown shrimp in the Gulf of Mexico reveal a pattern of spikes in prices of large shrimp compared to smaller ones in the late spring and summer — when the dead zones occur.11
“Because fishermen are catching more small shrimp and fewer large ones during these months, the price of small shrimp goes down and the price of large ones goes up, creating a short-term disturbance in the market that we can track,” study author Martin D. Smith at Duke’s Nicholas School of the Environment explained.12 But that’s only one of the risks of agricultural pollution to U.S. waterways.
65% of US coastal waters degraded by excessive nutrients
Excess nitrogen and phosphorus from agricultural fertilizer runoff and other sources have led to moderate to severe degradation in 65% of the estuaries and coastal waters in the U.S., according to NOAA.13 The excess nutrient load kicks off a process known as eutrophication, fueling the growth of large algae blooms.
Some of the algae is toxic in itself, but they also form large mats that block sunlight from reaching the water. When the algae die, the problems only get worse, as the decomposing biomass sucks dissolved oxygen out of the water near the bottom, leading to hypoxic, low-oxygen zones. Any creatures that aren’t able to swim away may suffocate and die.14
Eutrophication can also cause the production of carbon dioxide, which leads to a lowered pH in seawater sometimes referred to as ocean acidification. “This slows the growth of fish and shellfish, may prevent shell formation in bivalve mollusks, and reduces the catch of commercial and recreational fisheries, leading to smaller harvests and more expensive seafood,” NOAA explains.15
Further, at least one study has found that hypoxia in the northern Gulf of Mexico could reduce the abundance of Atlantic croaker by 25 percent over a 140-year period.16
Various solutions have been proposed, including enlisting farmed oysters to help reduce nutrients in the water.17 However, their efficiency at removing nutrients was comparable to that achieved by using agricultural and stormwater best management practices.
According to Louisiana State University marine ecologist Nancy Rabalais, who worked on forecasts that suggest the Gulf of Mexico dead zone could be even larger in scale than NOAA’s estimate at 8,717 square miles in summer 2019, treating the problem at its source — in the farms and cities of the Mississippi watershed — is the only long-term solution to stopping the Gulf of Mexico dead zone.18
Fertilizer runoff reductions needed to shrink Gulf dead zone
An intergovernmental panel devised an action plan to reduce fertilizer runoff so the Gulf of Mexico dead zone can shrink to 1,950 square miles by 2035. To achieve this, a study that used four computer models, published in PNAS, found a 59% reduction in nitrogen runoff to the Mississippi River will be necessary.19
Study author Professor Emeritus Don Scavia, at the University of Michigan, put it quite clearly: “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.”20
Unfortunately, according to LSU, “No reductions in the nitrate loading from the Mississippi River to the Gulf of Mexico have occurred in the last few decades.”21
While it’s easy to understand the massive effect a large river like the Mississippi has on waters downstream, small streams and wetlands also play an important role in larger downstream waterways. This even includes small streams that only flow after heavy rainfall.
This revelation came from a U.S. Environmental Protection Agency (EPA) report, which reviewed more than 1,200 peer-reviewed scientific studies.22 The study “unequivocally demonstrates that streams, regardless of their size or frequency of flow, are connected to downstream waters and strongly influence their function.”23
In addition, wetlands, floodplains and open waters in transitional areas located between land and water ecosystems (known as riparian areas) act as buffers in helping protect downstream waters from pollution.
Wetlands and floodplains not in riparian areas were also found to affect the integrity of downstream waters, even when they lacked surface water connections. “Some potential benefits of these wetlands are due to their isolation rather than their connectivity,” the report noted.
Intensive ag contributes most nitrogen pollution to river basin
It’s not surprising that areas with an abundance of agriculture, like the state of Iowa, would contribute more than their share of nitrogen pollution. One study published in PLOS One set out to quantify Iowa’s contribution of nitrogen pollution to the Mississippi river,24 which was named the second-most polluted waterway in the U.S. in 2012.25 In 2019 it’s the seventh-most polluted river in the world.26
There are well over 14,000 concentrated animal feeding operations (CAFOs) in Iowa, primarily medium and large in size and housing pigs.27 Genetically engineered corn and soy crops are also prolific. In the 2016 State of the River Report by the Mississippi National River and Recreation Area,28 the greatest source of chemical contamination to the river was found to be agricultural runoff.
For the PLOS One study, stream nitrate and discharge data were collected from 1999 until 2016 at 23 Iowa stream sites near watershed outlets. The results confirm that much of the nitrates devastating the Mississippi river are coming from Iowa. Iowa contributes an average of 29% of the nitrate load to the Mississippi-Atchafalaya Basin, 45% to the Upper Mississippi River Basin and 55% to the Missouri River Basin.
The amount of nitrates Iowa contributes to the Mississippi is larger than would be expected for the amount of water flowing into rivers in the area. While Iowa is one of 12 states that committed to a nutrient-reduction strategy to try to stop the Gulf of Mexico dead zone from worsening, the study notes, this “will be very difficult to achieve if nitrate retention cannot be improved in Iowa.”29
Regenerative, grass fed, biodynamic agriculture is the answer
The solution to reducing the Gulf of Mexico dead zone lies in changing agricultural practices from industrial to regenerative. Choosing grass fed products like grass fed beef and bison over those raised in CAFOs is one solution that we can all take part in. Choosing biodynamically grown food is another positive solution that can improve fertilizer runoff and the environment as a whole.
The use of regenerative agriculture techniques like cover crops and no-till farming, which improve soil health and reduce runoff and the need for chemical fertilizers and herbicides, which then benefits waterways, is essential, as is looking for alternatives to growing corn for ethanol. According to the PNAS study:30
“With little documented progress in loads or hypoxic extent, clearly something more or something different is needed. Several analyses have demonstrated a range of approaches and potential pathways toward the desired load reduction, including altering fertilizer application rates, using cover crops, nutrient management, alternatives to corn-based biofuels, and combinations of the above.
Most of these studies emphasize the value of targeting funding to locations and practices that make the most difference. It is time to ask what is preventing more extensive implementation of some or all of these strategies.”
Sourcing your foods from a local grass fed, biodynamic farmer is one of the best ways to take part on an individual level to stop the growing dead zone in the Gulf of Mexico.