Bees, butterflies pollinating less because of diesel and ozone

London - Air pollution may be reducing the pollinating abilities of bees and butterflies by preventing them from sniffing out flowers that depend on them, new research has shown.

Scientists from the University of Reading, the UK Centre for Ecology and Hydrology, and the University of Birmingham found there were up to 70 percent fewer pollinators and 90 percent fewer flower visits when diesel exhaust pollutants and ozone were present.

The study, published in the journal Environmental Pollution, is the first to confirm a negative impact of air pollution on pollination in the natural environment. The theory is that the pollutants react with and change the scents of flowers, making them harder to find.

Researchers knew from previous lab studies diesel exhaust have negative effects on insect pollinators, but the impacts they found in the field were much more dramatic than they had expected.

The findings are worrying because the air pollution is becoming more prevalent in the air most people breathe every day around the world.

Researchers say they knew pollutants are bad for people’s health and the significant reduction in pollinator numbers and activity shows there are clear implications for the natural ecosystems people depend on.

Previous studies by the Reading academics have shown diesel fumes can alter floral scents. The work suggested that pollution could contribute to the ongoing declines in pollinating insects, by making it harder for them to locate their food which includes pollen and nectar.

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

The researchers used a purpose-built fumigation facility to regulate levels of nitrogen oxides present in diesel exhaust fumes and ozone in an open field environment. They then observed the effects these pollutants had on the pollination of black mustard plants by free-flying, locally-occurring pollinating insects over the course of two summer field seasons.

They used pollution concentrations well below maximum average levels equating to 40 to 50 percent of the limits currently defined by US law as safe for the environment

This pales in comparison with the far higher levels of pollution that occur around the world due to breaches of regulations.

For example, outside of London, a 2019 analysis showed illegal levels of nitrogen dioxide were recorded in large areas England.

Observations revealed there were 62 to 70 percent fewer pollinator visits to the plants located in polluted air. This reduction was seen in seven pollinator groups, particularly bees, moths, hoverflies and butterflies.

There were also 83 to 90 percent fewer flower visits by these insects, and ultimately a 14 to 31 percent reduction in pollination, based on seed yield and other factors.

Such findings could have wide ranging implications because insect pollination delivers hundreds of billions of pounds worth of economic value every year.

It supports around 8 percent of the total value of agricultural food production worldwide, and 70 percent of all crop species, including apples, strawberries and cocoa, rely on it.