Bees and butterflies are getting confused in polluted air, reducing pollination: study

A new study has found that air pollution from urban and rural environments may be harming the pollination abilities of insects like butterflies and bees by stopping them from sniffing out wildflowers and crops that depend on them.

The U.K. study, published Wednesday in the journal Environmental Pollution, found that common air pollutants like nitrogen oxides emitted from diesel exhausts can chemically alter floral odours, disrupting the cues that certain insects need to find and pollinate flowers.

Researchers from the University of Reading, the U.K. Centre for Ecology & Hydrology and the University of Birmingham found that there were up to 70 per cent fewer pollinators and up to 90 per cent fewer flower visits when common air pollutants found on ground level were present. An overall pollination reduction of up to 31 per cent was also observed in test plants.

“We knew from our previous lab studies that diesel exhaust can have negative effects on insect pollinators, but the impacts we found in the field were much more dramatic than we had expected,” said project lead Robbie Girling in a news release.

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Previous studies conducted by members of the University of Reading team have shown that diesel fumes can alter floral odours, and the new study is the first to observe a negative impact by the pollutants on pollination in nature.

The new research also suggests that pollution could be contributing to the ongoing decline in pollinating insects by making it more difficult to find food sources, nectar and pollen.

“The findings are worrying because these pollutants are commonly found in the air many of us breathe every day. 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,” said study lead James Ryalls in the release.

The study used a specially built fumigation facility to pump regulated levels of nitrogen oxides into an open field environment and then observed the effects these pollutants had on the pollination of black mustard plants on free-flying, locally occurring pollinating insects over two summer field seasons.

Researchers used pollution concentrations well below the maximum average levels, approximately 40 to 50 per cent of the limits currently designated as “safe for the environment” by U.S. laws, which “pale in comparison” according to the release of the far higher levels of pollution that occur globally due to breaches in regulations.

The study found there were 62 to 70 per cent fewer pollinator visits to the plants located in the polluted air, and this reduction was seen in seven groups – particularly bees, moths, hoverflies and butterflies. There were also 83 to 90 per cent fewer flower visits by these insects and overall a 14-to-31-per-cent reduction in pollination based on data from seed yield and other factors.

The research is part of continuing studies into the effects of air pollutions on insect health and the environment.

“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,” said study co-author Christian Pfang in the release.

The results of the study indicate that air pollutants at levels currently deemed by legislation to be safe for the environment can cause significant reductions in insect-provided pollination, and the researchers wrote that further studies should be done to prioritize investigations into the broader ecological and economic consequences of pollution disruption of pollination.