A mandated interstate “pollution diet” intended to reduce nutrient runoff into the Chesapeake Bay is paying off, while voluntary measures to reduce nitrogen levels in Mississippi River have failed, writes a University of Michigan professor at the site The Conversation. “From my perspective, when we compare these two approaches it is clear that voluntary measures are not even making modest dents in nutrient pollution,” says professor Donald Scavia, who has worked on the issue of “dead zones” for four decades.
The so-called dead zones are created when nitrogen and phosphorus in runoff from farms, water treatment plants and other sources promote rapid growth of algae, which eventually sinks to the bottom and depletes the oxygen content of water as it decays. Oxygen levels are low enough to kill fish. The dead zone in the Gulf of Mexico is forecast to be the third-largest this year in 32 years of of monitoring.
States in the Mississippi River basin and around Lake Erie “rely primarily on voluntary steps, such as offering grants to farmers to take steps to prevent fertilizer from washing off their fields,” writes Scavia. “In contrast, states around the Chesapeake have had more success with a federally enforced plan that can impose mandatory actions across the bay’s 64,000-square-mile watershed.” The dead zone in the Chesapeake Bay is much larger than the target set by officials but “at least the Chesapeake is moving in the right direction.” Since the EPA wrote its “pollution diet” for the watershed, nitrogen runoff is down by 8 percent, phosphorus down by 20 percent and sediment down by 7 percent, says Scavia.
“Taming nutrient pollution will require a broad national approach that includes steps such as modifying the American diet, changing agricultural supply chains and reducing production of corn-based ethanol. We also need to find the will to set legally binding limits when voluntary steps aren’t enough,” he concludes, after noting, “Governments generally are averse to imposing environmental regulations on farmland.”