Is air pollution responsible for the global decline in insect numbers?

New research, by teams from the University of Melbourne, Beijing Forestry University and the University of California Davis, suggests that particulate matter affects an insects ability to find food or a mate and that it might only take 12 hours of exposure to high levels of air pollution for this damage to be caused.

Noting that, while related research into the affect of air pollution on insects has been carried out in the past, ‘Currently, there is little, if any, information about the effects of the more frequent short-term and lower pollution level exposure events, which happens more frequently and commonly under natural conditions.’

The researchers used neural tests to establish that contamination of the antenna significantly reduced the strength of odour-related electrical signals sent to the flies’ brains, essentially having a detrimental impact on their sense of smell.

Houseflies which had been exposed to varying levels of air pollution in Beijing were placed in a Y-shaped tube ‘maze’ with one arm leading to a smell of food or sex pheromones. The chosen route appeared arbitrary, with the flies having no more than a 50:50 likelihood of choosing to follow the odour. Uncontaminated flies on the other hand, typically headed towards the source of the smell.

Professor Mark Elgar, who co-authored the paper, said the study was alerting humans to a potentially significant risk to insect populations: ‘While we know that particulate matter exposure can affect the health of organisms, including insects, our research shows that it also reduces insects’ crucial ability to detect odours for finding food and mates.

‘This could result in declining populations, including after bushfires and in habitats far from the pollution source.

‘As well as being fascinating creatures, many insects play a critical role in pollinating plants – including almost all the crops we rely on for food – and breaking down decaying material and recycling nutrients.’

Continuing research in bushfire-affected areas in Australia has shown that the antennae of a variety of insects, including bees, wasps, moths and species of flies, are contaminated by smoke particles, even at considerable distances from the fire itself.

Professor Elgar s again: ‘When their antennae become clogged with pollution particles, insects struggle to smell food, a mate, or a place to lay their eggs, and it follows that their populations will decline.

‘About 40 per cent of Earth’s landmass is exposed to particle air pollution concentrations above the World Health Organisation’s recommended annual average and this includes many remote and comparatively pristine habitats and areas of ecological significance – because particulate material can be carried thousands of kilometres by air currents.’

The full paper can be read here