The number of square miles that make up the Gulf of Mexico's "dead zone" of low to no oxygen — roughly the size of New Jersey — as measured in July by the National Oceanic and Atmospheric Administration, compared to the five-year average of 4,298 square miles.
The dead zone, which can kill fish and other marine life, occurs every summer and is caused in large part by nutrient runoff from the overapplication of fertilizer on Midwestern farms.
