New research suggests that declines in wild bees may be due to a common class of pesticides.
The pesticides, called neonicotinoids, are already the subject of great controversy; many have already been banned in Europe in order to protect bees. U.S. regulators allow their continued use, mostly in the form of treated seeds, as most evidence of their harm came from lab studies — until now.
The new study proves the pesticide reduces bee populations under real-world conditions, and also casts doubt on a truism that bees would avoid the treated plants due to bad taste. In fact the poor bees, high on the pesticide, actually preferred the neonicotinoid taste and fed more off treated plants. Neonicotinoids have remained controversial for so long mostly due to the lobbying efforts of pesticide manufacturers, but the truth is, there are other documented dangers.
A pair of 2012 studies documented a separate danger posed by neonicotinoids. These studies, also performed under field conditions, documented how bees and other pollinators exposed to lower doses of neonicotinoids became lost more frequently, failing to return to their colony. One of the studies demonstrated that colonies exposed to neonicotinoids shrank much more than control groups, possibly due to the loss of those disoriented individuals who failed to return. More alarming, the exposed colonies produced fewer queens, making the establishment of new colonies more difficult.
Perhaps the biggest unresolved issue, however, is that pollinators are under stress from multiple sources. Neonicotinoids could be globally banned tomorrow and pollinators would still be in danger. A major factor is the monocultural, homogenized layout of modern agricultural fields. These homogenous fields have few promising locations for a colony to set up, forcing pollinating insects to travel farther and burn more energy. Effective herbicides eliminate weeds and wildflowers, destroying alternate food sources for pollinators and reducing pollinator diversity in agricultural fields.
And now, in this new, inhospitable landscape, we add neonicotinoid exposure. Many researchers believe that the cumulative impact of multiple factors might be driving pollinator declines. The elephant in the room is the impact on domestic honeybees, which provide most of the crop services. Colony Collapse Disorder (CCD) and other maladies of domestic bees have not been definitively tied to neonicotinoids.
Most food crops are pollinated by wind, so there are few examples of crop failures due to wild pollinator declines that can jog people to attention. Until crops start failing — and money is lost — there is little incentive to protect bees and other pollinators.