Air pollution threatens insect populations

New research conducted by the University of Melbourne, Beijing Forestry University, and the University of California Davis reveals that the impact of air pollution on insect health and reproduction is more significant than previously understood. This discovery suggests that air pollution may be contributing to the global decline in insect populations, even in remote wilderness areas. The researchers found that when insects’ antennae are contaminated by particulate matter from sources such as industry, transport, and bushfires, their ability to find food and mates is reduced.

The study, published in Nature Communications and co-authored by Professor Mark Elgar from the University of Melbourne, highlights the potential risk that air pollution poses to insect populations. While it is known that particulate matter exposure can harm organisms, including insects, this research demonstrates that it also impairs insects’ crucial sense of smell, which is vital for locating food and mates. This could lead to declining populations, even in habitats far away from pollution sources.

The research team conducted various experiments to support their findings. Using a scanning electron microscope, they observed that as air pollution levels increase, more particulate matter accumulates on the sensitive antennae of houseflies. This material consists of solid particles or liquid droplets suspended in the air, which can contain toxic heavy metals and organic substances from sources like coal, oil, petrol, or woodfires.

To further investigate the effects of air pollution on insects, the researchers exposed houseflies to different levels of air pollution for 12 hours in Beijing. They then placed the flies in a Y-shaped tube “maze.” Typically, uncontaminated flies would choose the arm of the maze that leads to the scent of food or sex pheromones. However, contaminated flies selected an arm randomly, with a 50:50 probability.

Neural tests confirmed that contamination of the antennae significantly reduced the strength of odor-related electrical signals sent to the flies’ brains, compromising their ability to detect odors.

Furthermore, ongoing research conducted in bushfire-affected areas in rural Victoria revealed that smoke particles contaminate the antennae of various insects, including bees, wasps, moths, and flies, even at considerable distances from the fire front.

Insects rely on their antennae, which contain olfactory receptors, to detect odor molecules from food sources, potential mates, and suitable egg-laying sites. When particulate matter covers the antennae, it creates a physical barrier that hinders contact between the smell receptors and airborne odor molecules.

“When pollution particles clog their antennae, insects struggle to detect the smell of food, mates, or egg-laying sites, ultimately leading to population decline,” explained Professor Elgar. “Approximately 40% of Earth’s landmass experiences particle air pollution concentrations higher than the World Health Organization’s recommended annual average.”

Surprisingly, this includes many remote and ecologically important habitats, as particulate matter can be transported thousands of kilometers by air currents, as highlighted by Professor Elgar.

The findings of this research underscore the critical role insects play in pollination, decomposition, and nutrient recycling, and highlight the urgent need to address air pollution to safeguard insect populations and the ecosystems they support.

Source: University of Melbourne

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