A field trial found that levels of nitrogen oxides and ozone similar to those near roads led to a 70 per cent drop in the numbers of bees and butterflies on mustard plants

By Adam Vaughan

A marbled white butterfly (Melanargia galathea) feeding on a greater knapweed flower (Centaurea scabiosa)

robertharding / Alamy Stock Photo

Exposing bees, butterflies and other pollinators to air pollution severely impairs their ability to sniff out the plants they feed on. That could be bad news for both insect populations and the crops that rely on them for pollination.

Pesticides and land use changes are two of the biggest drivers of plummeting insect numbers, but a new field trial suggests that polluted air caused by diesel cars may be a major cause too.

Previous evidence from lab studies has shown how air pollutants degrade the floral odour particles released by plants, making it harder for insects to locate them.

To gain a better handle on how those interactions play out in the wider environment, James Ryalls at the University of Reading, UK, and colleagues ran a three-year field trial. They built a system that generated nitrogen oxides and ozone pollution in the centre of a wheat field and piped it to six octagonal enclosures where black mustard plants were grown. Two more enclosures filled with ambient air acted as a control.

The results were stark. Levels of the pollutants on a par with average concentrations next to major UK roads led to a reduction in the number of pollinators counted on the plants by up to 70 per cent compared with the controls.