The insect population could be at significant risk of survival due to increased air pollution, a new international study has shown.
The research, published last week in the peer-reviewed journal Nature Communications, was part of a collaboration between Beijing Forestry University, the University of Melbourne, and the University of California Davis.
The report provides evidence that tiny particles originating from air pollution, especially from human-related sources, adhere to the sensory organs of insects, affecting their ability to mediate taste and smell. As a result, their capacity to locate food and reproduce decreases.
Specifically, the researchers demonstrated that "clean" houseflies that did not suffer from air pollution found their food source quickly and easily, explained Dr. Ittai Renan, director of Israel's National Ecosystem Assessment Program and head of the Applied Entomology Lab in the Steinhardt Museum at Tel Aviv University. In contrast, flies exposed to air pollution accumulated on their sensory organs struggled to identify food sources and experienced a decline in reproduction.
Renan was not involved in the study.
How does air pollution mess with insect sensory organs?
The sensory organs of insects appear as fine threads, Renan said. However, they are covered with grooves, pits, and hair-like structures that trap the tiny particles (particulate matter) from air pollution, including from industry, transport, bushfires, and more - primarily human-made.
Particulate matter can include solid particles or liquid droplets, from toxic heavy metals to organic substances from coal, oil, and petrol. The researchers found that the higher the level of air pollution, the more matter was collected.
Although the research focused mainly on houseflies, additional tests were conducted on other insects using an electron microscope with similar results.
Most humans are averse to pesky insects, but they play a critical role in the ecosystem.
"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," said Prof. Mark Elgar, who co-authored the paper, in a release published by Science Daily.
In addition, other animals rely on insects for food, such as birds and reptiles.
Around 99% of the global population already breathes air that exceeds the World Health Organization's air pollution guidelines, WHO said. The Nature Communications report noted that 40% of Earth is exposed to annual particulate matter concentrations that exceed WHO recommendations.
"The ongoing massive decline in the insect kingdom around us might be attributed to a newly discovered factor that was previously unknown," Renan said. "The collapse of the insect population, which is the largest and oldest group of animals on Earth, is also linked to the disappearance of entire species and a decrease in the overall insect population."
The study marks the first time that the detrimental effect of pollution on insects' olfactory capabilities has been scientifically proven, according to Renan.
He noted that data had been collected over the past five years, highlighting a steep decline in insect numbers. In Israel, a program for monitoring butterflies reported a sharp decline over the past few years. A more comprehensive program for monitoring insects has been implemented in the past two years, although research results are not yet available.
Renan said it is estimated that there has indeed been a decline in the overall insect population in Israel.
"The sources of pollution are proliferating, and their impact on insects is likely significant," Renan added. He said whether insects will ultimately adapt to these new pollution levels remains to be seen.
There is an "urgent need to address and mitigate pollution sources to protect these vital components of our ecosystems," Renan concluded.