Since the widespread adoption of man-made fertilizers in the 1950s – the innovation behind the “green revolution” – fertilizer and pollution runoff has caused hypoxia to increase in many shallow waters. By one estimate, the number of dead zones worldwide has doubled every 10 years since the 1960s, to 170. The US has about 50 hypoxic areas affecting half its estuaries. As developing countries continue to adopt industrial-scale farming methods, many foresee the problem spreading.
The Gulf dead zone has grown steadily, doubling in average size between 1980 and 2000. Scientists expect it to get bigger. More fertilizer than ever is washing down the Mississippi due to the ethanol boom and heavy rains. This year scientists predict a Massachusetts-sized dead zone, nearly 20 percent larger than the previous record of 2002. Chronic hypoxia has completely altered places like Chesapeake Bay and the Black Sea. No one knows how the Gulf’s hypoxic zone might affect the area’s lucrative fisheries.
“We’re ... playing roulette with the Gulf fisheries,” says Doug Daigle, coordinator of the Lower Mississippi River Sub Basin Committee on Hypoxia in Baton Rouge, La. “The big fear is that we’ll have a crash.… Once that happens, it’s very hard to try to go back and fix it.”
The problem, which embraces the 1.2 million-square-mile Mississippi watershed, spread across 31 states, is daunting. But a recent US Geological Survey report indicated that the fertilizer sources are relatively concentrated. Nine states contribute 75 percent of the nutrient runoff that ends up in the Gulf. Each year, $391 million worth of fertilizer washes down the Mississippi, according to the nonprofit Environmental Working Group (EWG) in Washington.