As we spend summer after summer swatting them away, it’s hard to imagine that one day they could be gone for good.
But flies’ sex lives have been blighted by air pollution as many species suffer from “dysfunctional” mating signals, a study warns.
Disturbing new research has revealed that flies struggle to be attracted to mating partners amid ozone pollutants that “drastically corrupt” their reproductive behavior.
The results come at a time when shrinking insect populations are a global concern, with flies essential for the pollination of 80 percent of the world’s crops.
Flies exposed to ozone on display “unusual courtship behavior” in which males are more attracted to their male counterparts and seemingly unable to distinguish between genders.
Flies were found to display an ‘unusual courtship behavior’ when exposed to ozone
“We knew that elevated ozone levels could affect insect mating systems because the breakdown of carbon double bonds, and thus pheromones, through oxidation is not rocket science in chemistry,” said researchers Nanji Jiang and Markus Knaden of the Max Planck Institute for Chemical Engineering and Chemistry. Ecology.
‘Still, we were shocked that even slightly increased ozone concentrations had such a strong effect on flight behaviour.’
Ozone gas is harmful to human health and, in addition to inflammation of the eyes, nose, airways and throat, can also cause asthma attacks.
Although it was present in the lower atmosphere in pre-industrial times, experts said its values were only 10 parts per billion (ppb), compared to today’s values of 40 ppb.
Recently, ozone also peaked at 210 ppb in Mexico, according to a separate article JGR spheres study, thanks to a mix of climate change and continued emissions of nitrogen oxides.
As part of the study, flies were placed in an “ozone exposure system” that mimicked levels of air pollution felt in cities during the summer.
When exposed to 100 ppb of the pollutant for just two hours, scientists saw levels of chemical attractants drop significantly among the flies.
Ozone-affected males were also observed to line up in “long courtship chains” that were said to be quite enigmatic.
Other fly species that rely more on visual cues for mating than on pheromones did not change their behavior.
Dr. Jiang and Dr. Knaden added: ‘We could explain that males courted each other after a brief exposure to ozone because they clearly could not distinguish between males and females that had been ozonized.
The Max Planck Institute study placed flies in an “ozone exposure system” that mimicked levels of air pollution in cities during the summer. Pictured: Formation of courtship chains of male fly species at 100 ppb for 20 minutes
Scientists believed that flies “could not distinguish” between females and males in the experiment
“However, we had not thought about this before.
“So we were quite surprised at the behavior of the ozone-exposed males, lined up in long courtship chains.”
Worryingly, Bill Hansson, co-founder of the Max Planck Center next Generation Insect Chemical Ecology, said it was “unlikely” that the flies would be able to adapt to the rapidly increasing air pollution.
He said: ‘Insects and their pheromones have evolved over millions of years. In contrast, the concentration of air pollutants has only increased dramatically since industrialization.
Pictured: Another male fly species (D. melanogaster) tested in ozone-enriched air
‘It is unlikely that insect communication systems, which have evolved over the course of evolution, can adapt to new conditions in a short period of time if there are suddenly no pheromones left. The only solution to this dilemma is to directly reduce pollutants in the atmosphere.’
Now scientists are trying to expand their research with a focus on other insects, including moths that commonly follow pheromone plumes over long distances.
Dr. Knaden added: ‘We would like to know whether high ozone levels lead to increased hybridization rates when closely related fly species share their habitat. Finally, chemical communication in insects is not limited to mating behavior.
‘All social insects such as bees, ants and wasps use chemical signals to identify members of their colony. We also investigate whether social structure within ant colonies is compromised when ants return from foraging trips that exposed them to elevated levels of pollutants.
“You don’t even want to imagine what happens when social structures in ant colonies or beehives suddenly collapse because pheromone communication no longer works.”
The ozone layer sits in the stratosphere 40 kilometers above the Earth’s surface and acts as a natural sunscreen
Ozone is a molecule made up of three oxygen atoms that occurs naturally in small amounts.
In the stratosphere, about seven to 40 kilometers above the Earth’s surface, the ozone layer acts like sunscreen, protecting the planet from potentially harmful ultraviolet rays that can cause skin cancer and cataracts, suppress the immune system and also damage plants.
It is produced in tropical latitudes and distributed all over the world.
Closer to the ground, ozone can also be created from photochemical reactions between the sun and pollution from vehicle emissions and other sources, creating harmful smog.
Although warmer-than-average weather conditions in the stratosphere have reduced ozone depletion over the past two years, the current area of the ozone hole is still large compared to the 1980s, when ozone depletion over Antarctica was first detected .
In the stratosphere, about seven to 40 kilometers above the Earth’s surface, the ozone layer acts as a sunscreen, protecting the planet from potentially harmful ultraviolet radiation
This is because levels of ozone-depleting substances such as chlorine and bromine remain high enough to cause significant ozone loss.
In the 1970s, it was recognized that chemicals called CFCs, used in refrigeration and aerosols, for example, were destroying the ozone layer in the stratosphere.
In 1987, the Montreal Protocol was agreed, leading to the phasing out of CFCs and, more recently, the first signs of recovery of the Antarctic ozone layer.
The upper stratosphere at lower latitudes is also showing clear signs of recovery, proving that the Montreal Protocol is working well.
But the new study, published in Atmospheric Chemistry and Physics, found that it probably doesn’t recover at latitudes between 60°N and 60°S (London is 51°N).
The cause is not certain, but the researchers believe it is possible that climate change is changing the pattern of atmospheric circulation, carrying more ozone away from the tropics.
They say another possibility is that very short-lived substances (VSLSs), which contain chlorine and bromine, could destroy ozone in the lower stratosphere.
VSLSs include chemicals used as solvents, paint strippers and as degreasing agents.
One of them is even being used in the production of an ozone-friendly replacement for CFCs.