Bees, this vital pollinator of nature, are disappearing.
Scientists are not entirely sure why. There is strong evidence linking the decline of bees to pesticides, but new research shows that another poison, long considered harmless to animals, could actually be indirectly killing these insects so essential on the planet.
A study carried out by scientists at the University of Texas at Austin (USA) suggests that the most widely used herbicide in the world, glyphosate (created by Monsanto, now owned by the pharmaceutical company Bayer) , could be a previously unknown factor of this collapse of the bee colonies. Glyphosate is the active ingredient in Monsanto’s best-selling herbicide, the “flagship” of the company’s agricultural chemicals business.
And this product is quite a business: a 2016 study found that, since its introduction in the 1970s, almost 10 million tons of glyphosate have been sprayed in fields around the world. That’s a lot; especially when this herbicide may be killing more than just weeds.
“We need better guidelines for glyphosate use, especially with respect to exposure to bees, because at this time the guidelines assume that bees are not harmed by the herbicide. Our study shows that this is not true,” says Erick Motta, leader of the work that publishes PNAS.
Glyphosate is suspected of being carcinogenic
The mechanism of action of glyphosate as a herbicide is the alteration of an important enzyme found in plants and microorganisms. Animals do not have this pathway, which is why the chemical was thought to be non-toxic to them. But what about the smaller organisms, like the gut bacteria that populate the microbiome of bees?
The scientists fed the bees a sugar solution with glyphosate, in a concentration that also occurs in the environment. They also had a second control group that received sugar without the popular herbicide. After three days, the bees that received the glyphosate cocktail had lost some of their benign gut bacteria , that is, they significantly reduced their healthy gut microbiota.
This reduction of good bacteria did not end there: in fact, it affected the survival of the bees.
When control bees and glyphosate-administered bees were exposed to the same bacteria, an opportunistic pathogen, Serratia marcescens , survival rates were markedly different.
Bees that had not been exposed to glyphosate saw their numbers halved after eight days; however , only a tenth of the bees exposed to glyphosate survived the pathogen after the herbicide.
“ Understanding these interactions is essential to quantifying the hazards associated with pesticide use and is essential if we are to develop strategies that allow us to continue using pesticides, which are vital to modern agriculture, while minimizing their effects on the natural world.” Motta clarifies.
For now, more research is needed to better understand how glyphosate is affecting the microbiome of bees and the health of other creatures, but researchers say we should no longer think that this herbicide is harmless to animals, even if it is just a Colony collapse disorder factor.
“It’s not the only cause of all these bee deaths, but it’s definitely something people should be concerned about because glyphosate is used everywhere,” Motta says.
Reference: Erick VS Motta el al., “Glyphosate perturbs the gut microbiota of honey bees,” PNAS (2018). www.pnas.org/cgi/doi/10.1073/pnas.1803880115
