Bees, butterflies and other insects get confused by common air pollution in urban and rural environments, and this leads to less pollination.

According to new research from the University of Reading, the University of Birmingham, and the UK Center for Ecology & Hydrology in the UK, scientists found there were up to 70% less pollinators, up to 90% fewer flower visits and a general pollination reduction of up to 31% in test plants solely based on common ground-level air pollution like ozone and diesel exhaust. Such air pollution significantly reduces pollination by preventing the insects to sniff out the wildflowers and crops that depend on them.

The theory is that the pollutants react with the scents of flowers and change them, so they are harder to find. The study was published in the journal Environmental Pollution. It is the first study to observe a negative impact of common air pollutants on pollination in the natural environment.

Dr. Robbie Girling, Associate Professor in Agroecology at the University of Reading, led the project. According to Girling, they knew from previous lab studies that diesel exhaust has negative effects on insect pollinators, but the impacts found in the field were much more dramatic than they expected.

This 6:09-minute video by CleanAir4V Network looks at Air Pollution Solutions with Dr. Christian Pfrang:



Dr. James Ryalls, a Leverhulme Trust Research Fellow at the University of Reading, conducted the study. According to Ryalls, the findings are worrying since these pollutants are found in the air many people breathe every day. These pollutants are bad for our health, and the significant decline in pollinator numbers and activity shows clear implications for the natural ecosystems we depend on.

Diesel fumes do alter floral odors, according to previous lab studies by members of the Reading team. This suggests that pollution contributes to the ongoing declines in pollinating insects, as it gets harder for them to locate pollen and nectar.

The impact of this in nature is less well understood, where insects pollinate important food crops and native wildflowers. Some pollinating insect species rely on scent more than others. This new study is to gather evidence to investigate how air pollution affects various of these species.

The study was funded by the Natural Environment Research Council. It used a purpose-built fumigation facility to regulate levels of nitrogen oxides (NOx) that is present in diesel exhaust fumes, and ozone, in an open field environment. They observed the effects these pollutants had on the pollination of black mustard plants by free-flying, local pollinating insects over the course of two summers.

They used pollution concentrations well below maximum average levels that equate to 40-50% of the limits currently defined by US law as environmentally safe.

This pales in comparison to the far higher levels of pollution occurring around the world due to breaches of regulations. Outside of London, a 2019 analysis showed illegal levels of nitrogen dioxide were recorded in local authorities in large areas of northern England, and south England.

Observations revealed 62-70% fewer pollinator visits to plants located in polluted air, particularly by seven pollinator groups including bees, moths, hoverflies, and butterflies. There were 83-90% fewer flower visits by these insects, and 14-31% less pollination, based on seed yield and other factors.

Such findings can have wide ranging implications. Insect pollination supports around 8% of the total value of agricultural food production worldwide, and 70% of all crop species, like apples, strawberries, and cocoa. Pollination delivers hundreds of billions of pounds worth of economic value every year.

Researchers at the University of Reading continue this research as part of continuing studies into the effects of air pollution on insect health and their interactions with the environment.

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