Scientists find there are 70% fewer pollinators, due to air pollution

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Air pollution drastically reduces pollination by confusing butterflies and bees, reducing their ability to detect crops and wildflowers

Insects pollinate important food crops and native wildflowers, but researchers have sought to understand how air pollution affects different species of pollinating insects, some of which rely on smell above all other senses. .

Scientists studying air pollutants from urban and rural environments found that there were up to 70% fewer pollinators, up to 90% fewer flower visits, and an overall 31% reduction in pollination in test plants when there were several common air pollutants at ground level. present – including pollutants from diesel exhaust and ozone.

Common air pollutants decrease insect pollination by preventing them from sniffing out dependent crops and wildflowers. Pollination accounts for about 8% of the total value of agricultural food production worldwide and contributes enormously to food security and the economy.

The study, published in Environmental pollution, highlights the negative impact of common air pollutants on pollination in the natural environment. The researchers speculated that the pollutants react with the scents of the flowers and alter them, making them harder to find.

Diesel fumes can alter floral odors

Pollution could contribute to the continued decline of pollinating insects, by making it more difficult for them to locate their food (pollen and nectar), and previous laboratory studies have shown that diesel fumes can alter floral odors.

The study used a specially designed fumigation facility to regulate levels of nitrogen oxides (NOX) – present in diesel exhaust – and open-field ozone. The researchers observed the effects of these pollutants on the pollination of black mustard plants by locally present free-flying pollinating insects during two summer seasons in the field.

The study only used pollution concentrations below the maximum average levels, which equates to 40-50% of the limits currently defined as environmentally safe by US law. These pollution concentrations are minor in comparison to the much higher pollution levels that occur around the world due to regulatory violations.

In 2019, outside London, an analysis found that illegal levels of nitrogen dioxide had been recorded in local authorities across large areas of northern England, including Cheshire and Gateshead, and southern England. England, including Wiltshire, Chichester and rural areas such as the New Forest.

“The impacts we found on the ground were much more dramatic than we expected.”

Dr Robbie Girling, associate professor of agroecology at the University of Reading, who led the project, said: “We knew from our previous laboratory studies that diesel exhaust can have negative effects on pollinating insects, but the impacts we found in the field were much greater. more dramatic than we expected.

Dr James Ryalls, a Leverhulme Trust researcher at the University of Reading, who conducted the study, added: “The results are worrying because these pollutants are commonly found in the air that many of us breathe every day. . We know these pollutants are bad for our health, and the significant reductions we’ve seen in the number and activity of pollinators show that there are also clear implications for the natural ecosystems we depend on.

70% of all cultivated species depend on pollination

Data analysis revealed that there were 62-70% fewer pollinator visits to plants located in polluted air.

This decrease was seen in many pollinator groups – particularly bees, moths, hoverflies and butterflies – and based on seed yield and other factors there was also 83-90% less visits to flowers by these insects, and ultimately a reduction of 14 to 31% pollination.

The researchers predict these findings will have wide-ranging implications, as insect pollination provides hundreds of billions of pounds of economic value each year. It supports around 8% of the total value of agricultural food production worldwide, 70% of all crops – including apples, strawberries and cocoa – depend on it.

Dr Christian Pfrang, Reader in Atmospheric Science at the University of Birmingham and co-author of the study, said: ‘This truly interdisciplinary work has demonstrated very clearly how air pollutants negatively impact pollination with direct consequences for food production as well as the resilience of our natural environment.

Scientists from the University of Reading, the UK Center for Ecology and Hydrology and the University of Birmingham are continuing to study the effects of air pollution on insect health and their interactions with the environment.

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