Tom Philpott recently posted at Mother Jones about what might politely be called one of the “unintended consequences” of genetically modified crops. As he writes, a new scientific study
found that overall, GMO technology drove up herbicide use by 527 million pounds, or about 11 percent, between 1996 (when Roundup Ready crops first hit farm fields) and 2011. But it gets worse. For several years, the Roundup Ready trait actually did meet Monsanto’s promise of decreasing overall herbicide use—herbicide use dropped by about 2 percent between 1996 and 1999, [studey author Chuck] Benbrook told me in an interview. But then weeds started to develop resistance to Roundup, pushing farmers to apply higher per-acre rates. In 2002, farmers using Roundup Ready soybeans jacked up their Roundup application rates by 21 percent, triggering a 19 million pound overall increase in Roundup use.
Since then, an herbicide gusher has been uncorked. By 2011, farms using Roundup Ready seeds were using 24 percent more herbicide than non-GMO farms planting the same crops, Benbrook told me. What happened? By that time, “in all three crops [corn, soy, and cotton], resistant weeds had fully kicked in,” Benbrook said, and farmers were responding both by ramping up use of Roundup and resorting to older, more toxic herbicides like 2,4-D.