Published in the Nature Communications journal, the study examines the wild bee population relative to the use of the controversial neonicotinoids in the 18-year span of 1994-2011. Researchers discovered that extinction rates for bees parallel the use of the pesticide on plants, which are found throughout the country.
One of the co-authors, Dr. Nick Isaac, remarked, "The negative effects that have been reported previously do scale up to long-term, large-scale multi-species impacts that are harmful. 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."
The 34 species analyzed in the study saw a 10 percent population drop across the board, with five of the species seeing a decrease of 20 percent or more, and the most-impacted group seeing a 30 percent drop. Researchers say this indicates that half of the population decline could be attributed to the use of neonics.
"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 Dr. Ben Woodcock, lead author of the study. "But this correlation study suggests that once it’s 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."
The study reads, "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."
The Friends of the Earth (FOE) environmental group launched a petition to that end, calling on the Ace and True Value hardware companies to stop carrying the pesticides, as consumers grow more conscious of their devastating impact.
FOE said, "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."
In a separate study, the group found that toxic chemical use is declining in the US, with 23 percent of plants in the nation testing positive for the chemicals, a decline from 50 percent two years ago. FOE credits the drop in numbers to the hardware stores that stopped selling products that contain harmful pesticides, including neonicotinoids.
"It's nice to see the use of long-term data to look at trends in pesticide impacts over longer time scale." said Dara Stanley, plant ecology lecturer at the National University of Ireland Galway. "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."