Pesticides Impair the Brain Development of Baby Bees

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A bumblebee sucking nectar on an echinacea purpurea flower head
Bees are smartest in groups, relying on swarm intelligence to get things done. Alexandra Giese/Shutterstock

This is a bee brain. This is a bee brain on pesticides.

And that's a bad buzz for one of the world's most essential pollinators.

According to new research published in Proceedings of Royal Society B, bees suffer permanent and irreversible brain damage when exposed to pesticides.

The research, from Imperial College London, focused on the impact of pesticides on baby bumblebees. Already under siege from what scientists call "climate chaos," bumblebees are becoming an increasingly rare sight in gardens around the world. But pesticides may be even more harmful than an ever-warming planet in that they don't give a baby bumblebee's brain a chance to develop in the first place.

As study author Richard Gill of Imperial College London tells CNN, pesticides act a lot like a harmful substance might act on a human fetus in the womb.

"Bee colonies act as superorganisms, so when any toxins enter the colony, these have the potential to cause problems with the development of the baby bees within it," he explains. "Worryingly in this case, when young bees are fed on pesticide-contaminated food, this caused parts of the brain to grow less, leading to older adult bees possessing smaller and functionally impaired brains; an effect that appeared to be permanent and irreversible."

In other words, pesticides may be dumbing down bumblebees. And as adults, those compromised bees have a hard time doing basic bee things, like building a nest, navigating and — most importantly for all life on this planet — pollinating flowers and food crops.

Serving bees neonicotinoids

To understand how pesticides impact bumblebee brains, the researchers administered a heady cocktail to residents of a bumblebee colony: a nectar substitute laced with neonicotinoids. The latter is a class of pesticide that's still commonly used, despite increasing scrutiny from world governments, including an outright ban in the U.K.

The amount of neonicotinoids given to the bumblebees for the study was similar to quantities found in flowers in the wild. Afterward, researchers used microCT scans to peer deep into the brains of nearly 100 bees from the colony.They found unmistakable differences in bees that had been exposed to neonicotinoids. An essential part of their brain called the mushroom body was substantially smaller. Researchers suspect the mushroom body is the bee brain's learning hub, affecting its ability to understand and perform simple tasks.

The smaller the mushroom body, the less functional the bee.

If pesticides are used on the very flowers they pollinate, it's easy to see how we may have brought bees to their knees — even before you factor in climate change and habitat loss.

"We are still trying to figure out what roles these factors play and how they interact," Gill explains to CNN. "Pesticides are definitely a contributing explanation to why we are seeing declines."