The study found up to 70% fewer pollinators, up to 90% fewer flower visits and an overall pollination reduction of up to 31% in test plants.

According to new research, common air contaminants from both urban and rural settings may be limiting insect pollination abilities by preventing them from sniffing out the crops and wildflowers that rely on them.

When common ground-level air pollutants, such as diesel exhaust pollutants and ozone, were present, scientists from the University of Reading, the UK Centre for Ecology & Hydrology, and the University of Birmingham discovered that there were up to 70% fewer pollinators, up to 90% fewer flower visits, and an overall pollination reduction of up to 31% in test plants.

The study, which was published in the journal Environmental Pollution, is the first to show that common air pollutants have a deleterious impact on pollination in the natural environment. Pollutants, according to the hypothesis, react with and modify the odors of flowers, making them harder to find.

“We knew from our previous lab studies that diesel exhaust can have negative effects on insect pollinators, said Dr. Robbie Girling, Associate Professor in Agroecology at the University of Reading, who led the project, “but the impacts we found in the field were much more dramatic than we had expected.”

“The findings are worrying because these pollutants are commonly found in the air many of us breathe every day,” added Dr. James Ryalls, a Leverhulme Trust Research Fellow at the University of Reading who led the study, adding, “we know that these pollutants are bad for our health, and the significant reductions we saw in pollinator numbers and activity shows that there are also clear implications for the natural ecosystems we depend on.”

Previous laboratory experiments conducted by members of the Reading team have shown that diesel fumes can change floral odors. Pollution, according to this study, could contribute to the continuous losses in pollinating insects by making it more difficult for them to find their food – pollen and nectar.

The impact of this phenomenon in nature, where insects pollinate important food crops and native wildflowers, is less well understood, so this new study aimed to gather evidence to investigate how different pollinating insect species, some of which rely on fragrance more than others, are affected by air pollution.

The project, which was backed by the Natural Environment Research Council, employed a purpose-built fumigation facility to control levels of nitrogen oxides (NOx) and ozone in an open field environment. NOx is found in diesel exhaust emissions. Over the course of two summer field seasons, they studied the effects of these contaminants on the pollination of black mustard plants by free-flying, locally-occurring pollinating insects.

They employed pollutant concentrations that were substantially below maximum average levels, corresponding to 40-50% of the current legal limits for environmental safety in the United States.

This pales in comparison to the significantly higher levels of pollution that occur around the world as a result of regulatory violations. Outside of London, for example, a 2019 research found prohibited nitrogen dioxide levels in local authorities in significant regions of northern England, such as Cheshire and Gateshead, and southern England, such as Wiltshire, Chichester, and rural places like the New Forest.

Observations found pollinator visits to plants located in contaminated air were reduced by 62-70%,. Bees, moths, hoverflies, and butterflies were among the pollinator species that experienced a decline. Based on seed output and other parameters, these insects visited 83-90% fewer flowers, resulting in a 14-31% decline in pollination.

These results could have far-reaching consequences, as insect pollination contributes hundreds of billions of dollars to the global economy each year. Around 8% of the total value of agricultural food production is supported by it, and 70% of all crop species rely on it, including apples, strawberries, and cocoa.

“This truly cross-disciplinary work demonstrated very clearly how atmospheric pollutants negatively impact on pollination with direct consequences for food production as well as the resilience of our natural environment,” added Dr. Christian Pfrang, Reader in Atmospheric Science at the University of Birmingham and a co-author on the study.

Source: 10.1016/j.envpol.2022.118847

Image Credit: Getty

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