The near record-breaking Midwestern drought of 2012 shriveled corn crops and toasted pasture land. But it did have one positive side effect. The drought significantly reduced the size of the seasonal Gulf of Mexico dead zone. Less rain led to less fertilizer runoff—the dead zone is fed by a buildup of nitrogen-based fertilizer in the Gulf—which meant that the 2012 summer dead zone measured just 2,889 sq. miles. That’s still a zone the size of the state of Delaware, but it was the fourth-smallest dead zone on record, and less than half the size of the average between 1995 and 2012.
This year will be different. Heavy rainfall in the Midwest this spring has led to flood conditions, with states like Minnesota and Illinois experiencing some of the wettest spring seasons on record. And all that flooding means a lot more nitrogen-based fertilizer running off into the Gulf.