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Diesel Exhaust Throws Honeybees Off the Scent

Scientists find NOx pollution from vehicles can change the chemical makeup of flowery odors, affecting bees’ ability to find food.

Honeybees rely on their sense of smell as well as vision to locate a flower for the first time, but a new study suggests diesel exhaust could be disrupting odor cues, making it harder for bees to stay on course.

New research suggests diesel exhaust fumes change the scent of at least one flower that honeybees often frequent, making it more difficult for them to forage for nectar and possibly contributing to their decline.

Scientists from Britain’s University of Southampton combined eight chemicals found in the scent of the yellow oilseed rape flower and exposed samples to both clean and exhaust-filled air. Four of the flower chemicals reduced in volume when they mixed with the nitric oxide and nitrogen dioxide gases of diesel fumes, and two became undetectable within a minute, changing the chemical profile of the smell. When honeybees were exposed to a blend without the two chemicals that had most diminished, they were roughly half as likely to extend their tongues in search of nectar than they were for the full mixture.

While authors acknowledge that field observations are needed to establish that the same phenomenon happens in a natural environment and with other flower species, they also suggest that “degradation of an odor source by pollution is likely to be more pronounced at a distance from the flower,” making it even more likely that diesel’s reactive chemicals would hamper flower recognition outside the lab.

In the context of ongoing honeybee colony collapse and studies about the effects of a loss of pollination services, the authors conclude that diesel pollution, which can come from heavy equipment, generators, or diesel trucks and cars, could be “detrimental to pollinator health, particularly in conjunction with other stressors.”

Published November 1, 2013 Permalink

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