New evidence shows that the controversial pesticides known as neonicotinoids, or neonics, could be linked to bee population decline.
A new study, published Tuesday in the journal Nature Communications, looks at wild bee populations relative to the use of neonics on the oilseed rape plant in England over 18 years, from 1994-2011. The researchers found that population extinction rates went up along with the pesticide use on the plants, which are widespread throughout the country.
"The negative effects that have been reported previously do scale up to long-term, large-scale multi-species impacts that are harmful," Dr. Nick Isaac, a co-author of the report, told the BBC. "Neonicotinoids are harmful, we can be very confident about that and our mean correlation is three times more negative for foragers than for non-foragers."
Across the 34 species analyzed in the study, there was a 10 percent decline in populations attributable to neonic use, the BBC said. Five of the species dropped off by 20 percent or more, and the most affected group went down by 30 percent. In total, half of the population decline in wild bees could be linked to the pesticides, the researchers said.
"Historically, if you just have oilseed rape, many bees tend to benefit from that because it is this enormous foraging resource all over the countryside," said lead author Dr. Ben Woodcock. "But this co-relation study suggests that once its treated with neonicotinoids up to 85 percent, then they are starting to be exposed and it's starting to have these detrimental impacts on them."
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The researchers wrote in their study, "Our results suggest that sub-lethal effects of neonicotinoids could scale up to cause losses of bee biodiversity. Restrictions on neonicotinoid use may reduce population declines."
To that end, environmental group Friends of the Earth (FOE) launched a petition calling on the hardware companies Ace and True Value to stop selling toxic pesticides as consumers become increasingly aware of their dangerous side effects.
"If these garden retailers don't act fast, they'll lose customers. A new poll shows that 66 percent of Americans prefer to shop at Lowe's and Home Depot because they've committed to stop selling bee-killing pesticides," the group said.
FOE also found in a separate study that use of the toxic chemicals in the U.S. is declining, with just 23 percent of garden plants across the country testing positive for harmful pesticides, down from more than 50 percent two years ago. The environmental group credited the hardware stores that stopped selling products with neonics and other dangerous chemicals for the rapid drop in numbers—but warned that Ace and True Value were "clearly not taking the bee crisis seriously."
Dara Stanley, a plant ecology lecturer at the National University of Ireland Galway, told the Washington Post, "It's nice to see the use of long-term data to look at trends in pesticide impacts over longer time scale." (Stanley was not involved in the study.)
"That is something that has been missing in the debate on bees and pesticides so far, and there have been many calls to look at effects over time," Stanley said.