Scientists are expecting this year’s “dead zone” in the Gulf of Mexico to be one of the largest in recorded history because of alarming amounts of rainfall and pollution.
The oxygen-starved area, which gets its name from the difficulty of marine life to survive, is expected to grow to roughly the size of Massachusetts, or approximately 7,829 square miles, the National Oceanic and Atmospheric Administration said Monday.
This forecast is similar to one released Monday by Louisiana State University. The LSU forecast expects the dead zone, also called a hypoxic zone, to cover 8,717-square-miles, which is roughly the size of New Jersey.
“We think this will be the second-largest, but it could very well go over that,” Nancy Rabalais, a marine ecologist and co-author of the LSU report, told CNN.
NOAA’s estimate is slightly smaller than the record of 8,776 square miles seen in 2017, though it is larger than the five-year average of 5,770 square miles.
The federal agency blames unusually high amounts of spring rainfall and runoff pollution for the grim forecast.
Heavy rain has washed pollutants, including fertilizers, into rivers and streams that feed the Mississippi River and eventually the Gulf of Mexico. Once in the Gulf, these nutrients spark massive phytoplankton blooms that eventually die, sink to the bottom and decompose with the help of bacteria that consume the water’s oxygen supply, according to the government agency.
The Gulf Coast is particularly vulnerable to dead zones because 41% of the U.S. drains into the Mississippi River, whose watershed is largely composed of farmland, according to the Environmental Protection Agency.
The U.S. Geological Survey reported that during the entire month of May there was a total discharge of roughly 156,000 metric tons of nitrate and 25,300 metric tons of phosphorus into the Mississippi and Atchafalaya rivers. This is nearly 70% above the long-term average from 1980 to 2018, NOAA said.
University of Michigan aquatic ecologist Don Scavia, whose university contributed to NOAA’s forecast, urged that more needs to be done to prevent the runoff from getting into the waterways.
“While this year’s zone will be larger than usual because of the flooding, the long-term trend is still not changing,” he said in a news release. “The bottom line is that we will never reach the dead zone reduction target of 1,900 square miles until more serious actions are taken to reduce the loss of Midwest fertilizers into the Mississippi River system.”
Each year’s forecast may change depending on winds and waves that affect how the pollution disperses, NOAA noted. Last year’s dead zone forecast ended up being smaller than predicted because of such mixing.
Steve Thur, director of NOAA’s National Centers for Coastal Ocean Science, stressed the importance of such annual assessments at a time when rainfall within the Mississippi/Atchafalaya River Basin is expected to increase.
“This year’s historic and sustained river flows will test the accuracy of these models in extreme conditions, which are likely to occur more frequently in the future, according to the latest National Climate Assessment,” he said in a statement. “The assessment predicts an increase in the frequency of very heavy precipitation events in the Midwest, Great Plains, and Southeast regions, which would impact nutrient input to the northern Gulf of Mexico and the size of the hypoxic zone.”