Agriculture & climate change, Australia (Commonwealth Union) – New research conducted by the University of Melbourne, Beijing Forestry University, and the University of California Davis has revealed that the impact of air pollution on insect health and reproduction is more significant than previously understood. This pollution could be a contributing factor to the decline in global insect populations, even in remote wilderness areas.
The study indicates that particulate matter from various sources of air pollution, such as industry, transport, and bushfires, contaminates insects’ antennae, impairing their ability to find food and mates. Professor Mark Elgar from the University of Melbourne, a co-author of the paper published in Nature Communications this month, highlights that this reduced capacity to detect odors could lead to declining insect populations, even in habitats far from pollution sources.
Insects play crucial roles in pollination, including for almost all the crops essential for human food supply, as well as in breaking down decaying matter and recycling nutrients.
Insects, such as bees, butterflies, and other pollinators, are essential for pollinating flowering plants. They transfer pollen from one flower to another, enabling plants to produce fruits and seeds. This process is critical for the reproduction of many plant species, including those that provide food for humans and other animals.
Decomposition has a significant role for insects, such as beetles and flies, are vital in breaking down organic matter like dead plants and animals. Through the process of decomposition, they help recycle nutrients back into the soil, making them available for new plant growth. Without insects, dead plant and animal material would accumulate, leading to nutrient depletion and a disruption in the nutrient cycling process.
Certain insects are also natural predators of pests that can harm crops and plants. Ladybugs, praying mantises, and certain wasps, for example, feed on pest insects, helping to control their populations. By acting as natural pest controllers, insects play a crucial role in maintaining the balance of ecosystems and supporting agriculture.
The researchers conducted multiple experiments to investigate the effects of air pollution on insects:
They used a scanning electron microscope to observe that as air pollution levels increase, more particulate material accumulates on the sensitive antennae of houseflies. This material can include toxic heavy metals and organic substances from various sources, like coal, oil, petrol, or woodfires.
Houseflies exposed to varying levels of air pollution for just 12 hours in Beijing were placed in a Y-shaped tube ‘maze.’ Typically, uncontaminated flies would choose the arm of the maze leading to the smell of food or sex pheromones, while contaminated flies chose an arm randomly, with a 50:50 probability.
Neural tests verified that antenna contamination significantly reduced the strength of odour-related electrical signals sent to the flies’ brains, compromising their capacity to detect odors.
Furthermore, ongoing research in bushfire-affected areas in rural Victoria has shown that diverse insects, such as bees, wasps, moths, and flies, have contaminated antennae due to smoke particles, even at considerable distances from the fire front.
Insects rely on their antennae’s olfactory receptors to detect odors from food sources, potential mates, or suitable places for laying eggs. When particulate matter covers their antennae, it creates a physical barrier that hinders contact between the smell receptors and air-borne odor molecules. This leads to difficulties in smelling food, mates, or suitable egg-laying sites, ultimately impacting their population according to Professor Mark Elgar from the University of Melbourne, who is co-author of the paper.
The study highlights the global scope of the issue, with about 40% of Earth’s landmass exposed to particle air pollution concentrations above the World Health Organization’s recommended annual average as indicated by Professor Edgar. This includes remote and pristine habitats, as particulate material can travel long distances through air currents. The research raises concerns about the potential consequences for insect populations and the critical ecological roles they play in the ecosystem.
