Pollinators like bees and butterflies are responsible for one in every three bites we eat. These insects already face alarming declines due to habitat loss, pesticides and disease, but now, UK researchers have found that air pollution may be reducing their pollinating ability even further.
Their study, published in Environmental Pollution, observed that when ground-level pollutants like ozone and diesel exhaust fumes were in the air, there were up to 70% fewer pollinators, including bees, moths and butterflies.
This resulted in 90% fewer visits to flowers by these insects, and an overall reduction in pollination by 31%.
This is the first study to observe that air pollutants have a negative impact on pollination.
“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,” says project leader Robbie Girling, agroecologist at the University of Reading.
Other previous experiments in the lab have shown that diesel fumes can react with and change floral odours. This suggests that out in the wild, air pollutants may change the scents of flowers and make it more difficult for pollinators to find them.
So the team went out to study what goes on in the field, using a specially built fumigation facility that could regulate pollutant levels in an open environment. They elevated the levels of diesel exhaust and ozone, both together and individually, but kept the overall levels pretty low – at just 40-50% of the levels considered safe for the environment. This is well below the high and often illegal levels of pollutants such as nitrogen dioxide that occur around the world.
Then, over two summers, the team observed significantly reduced effects on the pollination of black mustard plants by local insects.
There were 62-70% fewer pollinator visits to the plants by pollinators, particularly bees, moths, hoverflies and butterflies, and an overall reduction of 14-31% in pollination.
“The findings are worrying because these pollutants are commonly found in the air many of us breathe every day,” says James Ryalls, co-author also from the University of Reading. “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.”
The results also demonstrate how atmospheric pollutants could have direct consequences on food production – which is a problem when 70% of all crop species rely on pollination, including 90 varieties of fruits, vegetables and essential crops.