Honeybees’ ability to find flowers is being hampered by air pollution, according to new research.
Tests showed even moderate levels of air pollutions break down floral scent chemicals which insect pollinators use to forage for food.
The modified odors confuse bees making it take longer for them to find their favourite plants.
This happens because the chemical interactions reduce both the scent molecules’ life span and the distances they travel.
Professor Jose Fuentes, of Pennsylvania State University, said: “Many insects have nests that are up to 3,000 feet away from their food source, which means scents need to travel long distances before insects can detect them.
“Each insect has a detection threshold for certain kinds of scents and they find food by moving from areas of low concentrations of scents to areas of high concentrations.”
While foraging, insects detect floral scent molecules in the air which can be carried by wind currents to hives thousands of feet away.
Hydrocarbons emitted by plants are broken down by ozone leading to more air pollutants including hydroxyl and nitrate radicals, which creates a vicious circle.
The researchers ran 90,000 computer simulations showing as pollution increases hydrocarbons’ lifetime and travel distance decreases.
For example, at 60 parts per billion ozone levels, which the US Environmental Protection Agency considers a ‘moderate’ level, enough chemical changes took place to thoroughly confuse bees and hinder their ability to identify the plumes of floral scents they needed to locate food.
The scent molecule alpha-pinene, which survives nearly 40 hours in a clean air environment, survived fewer than ten hours when ozone rose to 60 parts per billion and just one hour when it was at 120 parts per billion.
Another molecule, beta-myrcene, which travels more than 3,000 feet in an ozone free, windy environment, travelled an average of 1,500 feet when it was 60 parts per billion and, when it rose to 120 parts per billion, fewer than 1,000 feet.
In an ozone-free environment it took 10 minutes for 20 percent of bees to find the scent molecule beta-caryophyllene. When ozone rose to only 20 parts per billion, it took 180 minutes for the same amount of bees to find the scent. The team found similar results for the six different scent molecules they analysed.
Prof Fuentes said: “We found when we confused the bees’ environment by modifying the gases present in the atmosphere, they spent more time foraging and would bring back less food, which would affect their colonies.
“It is similar to being asked to get a cup of coffee at the nearest cafeteria while you are blindfolded.
“It will be hard to locate the coffee shop without using visual cues. The same could happen to insect pollinators while foraging for food in polluted air masses.”
As the concentration of scents changes drastically in air polluted environments, this could impact important interactions between plants and insects.
Prof Fuentes said it may lead to increases in the population of plants that do not rely on pollinators, and bee declines would lead to decreases in crop yields.
The findings published in Atmospheric Environment highlight air pollution is among many factors influencing the decline of the bee population.
According to research, managed honeybee populations in the US have fallen between 25 and 45 percent a year since 2010, including a 44 percent decline from 2015 to 2016. Britain’s bees are thought to have fallen by a third since 2007.
Added Prof Fuentes: “Honeybees and other pollinators are in trouble almost everywhere, and they pay us a lot of services through their pollination.
“The more we can understand about what factors are affecting their decline in numbers, the more equipped we will be to intervene if needed.”
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