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A buff-tailed bumblebee Bombus terrestris with pollen in its pile. (Source: WikiMedia Commons)

A buff-tailed bumblebee Bombus terrestris with pollen in its pile. (Source: WikiMedia Commons)

After years of controversy, researchers in Scotland have delivered solid evidence that neonicotinoid insecticides impair bee brain functions.

In previous studies, exposure to neonicotinoids has been shown to interfere with bees’ nervous systems, and some entomologists have theorized that this class of pesticide, along with climate change and zombifying parasites, is leading to the disappearance of bees worldwide.

A combination of laboratory and field studies undertaken by researchers at the Universities of St. Andress and Dundee has now shown that even low levels of neonicotinoids cause bumblebee colonies to have an estimated 55 percent reduction in live bee numbers and a 71 percent reduction in healthy brood cells. The study was recently published in the Journal of the Federation of American Societies for Experimental Biology.

“This is not proof that neonicotinoids are solely responsible for the decline in insect pollinators,” said Dr. Chris Connolly, a Reader in the Division of Neuroscience at Dundee’s School of Medicine, “but a clear linear relationship is now established. We can now be confident that at these levels, neonicotinoids disrupt brain function, bee learning and the ability to forage for food and so limit colony growth.”

Neonicotinoid contamination of nectar and pollen consumed by bees is about 2.5 parts per billion, or as Phys.org describes it, around one teaspoon in an Olympic swimming pool. Even at this level, the neonics were shown to quickly shut down the mitochondria in bumblee brain cells. At even lower levels, the researchers say, the brain cells exhibit impaired stimulation, leading to the bee struggling to learn or recognize the scent of flowers or even find their way home.

“Our research demonstrates beyond doubt that the level of neonicotinoids generally accepted as the average level present in the wild causes brain dysfunction and colonies to perform poorly when consumed by bumblebees,” said Connolly. “In fact, our research showed that the ability to perturb brain cells can be found at 1/5 to 1/10 of the levels that people think are present in the wild.

“This is not surprising as pesticides are designed to affect brains of insects,” he added, “so it is doing what it is supposed to do but on a bumblebee as well as the pest species. The bumblebees don’t die due to exposure to neonicotinoids but their brains cells don’t perform well as a result and this causes adverse outcomes for individual bees and colonies.”

Since 2006, beekeepers have reported significant drops in their hive populations, to the point that they are now losing an average of 30 percent of their hives per year. This has had a major impact on agricultural output and, subsequently agricultural prices, as bees and other pollinators “contribute nearly $27 billion to the U.S. economy and honeybees alone contribute nearly $20 billion to the U.S. and $217 billion to the global economy.”

That’s according to representatives from 118 businesses who petitioned President Obama to suspend the use of neonicotinoids last month. In their letter, the authors write that there have been over 30 scientific studies linking neonicotinoid use to nerve damage in bees. The European Union has already passed a two-year ban on three types of neocotinoids. Two of Ontario’s largest honey producers are currently embroiled in a $400 million class action lawsuit against Bayer Cropscience and Syngenta Canada over the claim that the companies’ neonics caused the deaths of their bee colonies.

Even previous to the St. Andrews-Dundee study, the U.S. government already took the evidence of neonic-poisoning to heart. Starting in January 2016, that class of insecticide will be banned from all federal wildlife refuges.

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