British Scientists Says Diesel Exhaust Stops Honey Bees from Finding the Flowers They Want to Forage

Exposure to common air pollutants found in diesel exhaust pollution can affect the ability of honey bees to recognize floral odors, new University of Southampton research shows.

Honey bees use floral odors to help locate, identify and recognize the flowers from which they forage.

The Southampton team, led by Dr. Tracey Newman and Professor Guy Poppy, found that diesel exhaust fumes change the profile of flora odor. They say that these changes may affect honey bees’ foraging efficiency and, ultimately, could affect pollination and thus global food security.

Published in Scientific Reports (3 October 2013) the study mixed eight chemicals found in the odor of oil rapeseed flowers with clean air and with air containing diesel exhaust. Six of the eight chemicals reduced (in volume) when mixed with the diesel exhaust air and two of them disappeared completely within a minute, meaning the profile of the chemical mix had completely changed. The odor that was mixed with the clean air was unaffected.

Furthermore, when the researchers used the same process with NOx gases (nitric oxide and nitrogen dioxide), which is found in diesel exhaust, they saw the same outcome, suggesting that NOx was a key facilitator in how and why the odor’s profile was altered. The changed chemical mix was then shown to honey bees, which could not recognize it.

Dr. Newman, a neuroscientist at the University, comments: “Honey bees have a sensitive sense of smell and an exceptional ability to learn and memorize new odors. NOx gases represent some of the most reactive gases produced from diesel combustion and other fossil fuels, but the emissions limits for nitrogen dioxide are regularly exceeded, especially in urban areas. Our results suggest that that diesel exhaust pollution alters the components of a synthetic floral odor blend, which affects the honey bee’s recognition of the odor. This could have serious detrimental effects on the number of honey bee colonies and pollination activity.”

Professor Poppy, an ecologist at the University, adds: “Honey bee pollination can significantly increase the yield of crops and they are vital to the world’s economy – £430 million a year to the UK alone. However, to forage effectively they need to be able to learn and recognize the plants. The results indicate that NOx gases — particularly nitrogen dioxide — may be capable of disrupting the odor recognition process that honeybees rely on for locating floral food resources. Honey bees use the whole range of chemicals found in a floral blend to discriminate between different blends, and the results suggest that some chemicals in a blend may be more important than others.”