Animals don't seem to be harmed by the world's most widely used weedkiller, but bees apparently don't fall under that protective umbrella. "This is really critical," one entomologist tells Science of a new study showing the digestive system of honeybees (and possibly other bees as well) may be adversely affected by glyphosate, the main ingredient in Monsanto's Roundup. Until now, the herbicide had been thought "innocuous" to animals because it targets an enzyme only plants and microorganisms produce. Now, however, it seems glyphosate also messes with the gut microbiome—the bacteria found in creatures' intestines that protects against "opportunistic pathogens"—which can ultimately make bees more vulnerable to infection, per the study published in the Proceedings of the National Academy of Sciences journal.
To test the herbicide's effects, biologist Nancy Moran's team fed 2,000 bees a sugar syrup, some laced with glyphosate. The bees that ingested the glyphosate mixture ended up with significantly lower levels of the gut bacteria Snodgrassella alvi. In later tests, just 12% of the glyphosate bees survived infection by an invasive bacteria; 47% of the non-herbicide-eating bees lived. The Guardian, meanwhile, cites previous research that found glyphosate seemed to have detrimental effects on honeybee larvae survival and on bees' cognitive functioning. Moran notes the S. alvi bacteria spits out a chemical that may be a fighter against other, invasive bacteria; it may also offer a protective shield by lining the gut wall. Per the Guardian, a Monsanto rep insists: "Claims that glyphosate has a negative impact on honeybees are simply not true." (Small signs of hope on the honeybee front.)