Oxygen-starved "dead zones" are spreading in U.S. coastal waters because of human activities, including the leap in corn ethanol production, said federal scientists in a new multiagency report.
Researchers say areas of hypoxic water, where fish and other marine life suffocate from the lack of oxygen, have boomed 30-fold in the U.S. since 1960, threatening the ocean food web and the country's fish and shrimp industries.
Incidence of hypoxia was found in half of the 647 areas analyzed, rising most prominently in the northern Gulf of Mexico.
The Gulf dead zone is the second largest oxygen-depleted area in the world, behind the Baltic Sea. It measured nearly 21,000 square kilometers in 2008, up from 4,000 square kilometers in the mid-1980s.
The dead zone swells each summer when nitrogen fertilizer runs off Midwestern cornfields, down the Mississippi River and into the sea. The excess nitrates breed algal blooms on the sea surface that quickly rot and sink. Tiny microbes feed off the dead algae, consuming oxygen and suffocating ocean-bottom dwellers. The process robs life forms higher up the food chain of sustenance.
Robert Diaz, an oceans expert at the Virginia Institute of Marine Science at the College of William and Mary, and a primary author of the study, told SolveClimate News:
"To reduce the dead zone we have to reduce nutrients coming out of the Mississippi."
Corn Ethanol Problem
Corn, which loses more nitrogen per acre than most crops, has long been the leading source of nutrient pollution. Mandates for grain-based ethanol have only added to the troubles, experts say.
"The push to grow corn ethanol worsened the problem ... though it's not the source of it," said Simon Donner, a geographer at the University of British Columbia, who was not involved with the study but has published peer-reviewed research on biofuels and the Gulf dead zone.
The Energy Independence and Security Act (EISA) of 2007 directs the U.S. to boost the use of biofuels from 12 billion gallons this year to 36 billion gallons by 2022. Some 15 billion gallons of that is expected to come from corn ethanol.
"Increased production of corn-based ethanol biofuel is projected to exacerbate hypoxia in the Gulf," scientists at the National Oceanic and Atmospheric Administration, the Environmental Protection Agency, the U.S. Geological Survey and the Department of Agriculture warned in their report.
"What the energy policy does is push things in the other direction," Donner told SolveClimate News. "It basically is encouraging more corn to be planted."
Donner said if the U.S. meets its corn ethanol goal, then nitrogen pollution in the Mississippi River would jump by seven to 15 percent.
"You're not going to solve the dead zone with an energy policy that says grow corn," he said.
The federal report suggests that cellulosic biofuels crops, like switchgrass and other perennial grasses, which require less nitrogen, could alleviate the dead zone.
"Research has already shown fewer environmental impacts if cellulosic feedstocks are used instead of corn," the report said.
Donner said he is skeptical that cellulosic ethanol production could reach commerical-scale anytime soon.
The EISA mandates that 16 billion gallons of fuel must come from cellulosic crops in just over a decade. Currently, there is not a single large-scale cellulosic plant in operation, however, compared with 189 corn ethanol facilities.
"It's the sort of the thing that everyone always talks about as sort of the next dream," Donner said. "But I don't see that as being a major factor right now."
The report, released on Friday by a working group of the joint subcommittee on Ocean Science and Technology, is the first U.S. scientific assessment of hypoxia since 2003.
While efforts to stem the tide of hypoxia "have not made significant headway" since then, the study firmly states that is possible to reverse the trend of increasing dead zones through changes in the way fertilizers are managed.
In the U.S., "every system, mostly small systems, have recovered that have had nutrient management applied," Diaz said.
The key solution, he explained, is for states and agricultural interests to make binding commitments to curb nutrients.
"For the dead zone to really move ahead in terms of being reduced, we're going to have to see a switch form an action plan that is voluntary to ... legal binding reductions on nutrients, sewage discharges and everything else that can be managed," Diaz said.
The other option is an economic solution, he said, which would ensure that farmers have an incentive to conserve. The economics of nitrogen runoff are not "quite right," he explained.
"If I was a farmer, I would hate to be losing all that nitrogen," Diaz said. "Perhaps if nitrogen cost three to four times what it does now you would see some kind of conservation."