Air pollution could be making honey bees sick – new study

A swarm of giant Asian honey bees. Rickythai/Shutterstock

Barbara Smith, Coventry University and Mark Brown, Royal Holloway

Whether it’s exhaust fumes from cars or smoke from power plants, air pollution is an often invisible threat that is a leading cause of death worldwide. Breathing air laced with heavy metals, nitrogen oxides and fine particulate matter has been linked to a range of chronic health conditions, including lung problems, heart disease, stroke and cancer.

If air pollution can harm human health in so many different ways, it makes sense that other animals suffer from it too. Airborne pollutants affect all kinds of life, even insects. In highly polluted areas of Serbia, for instance, researchers found pollutants lingering on the bodies of European honeybees. Car exhaust fumes are known to interrupt the scent cues that attract and guide bees towards flowers, while also interfering with their ability to remember scents.

Now, a new study from India has revealed how air pollution may be depleting the health of honey bees in the wild. These effects may not kill bees outright. But like humans repeatedly going to work under heavy stress or while feeling unwell, the researchers found that air pollution made bees sluggish in their daily activities and could be shortening their lives.

Unhealthy bees in Bangalore

India is one of the world’s largest producers of fruit and vegetables. Essential to that success are pollinator species like the giant Asian honey bee. Unlike the managed European honey bee, these bees are predominantly wild and regularly resist humans and other animals eager to harvest their honey. Colonies can migrate over hundreds of kilometres within a year, pollinating a vast range of wild plants and crops across India.

An exposed comb hive hanging from a tree branch.
A giant honey bee hive. Muhammad Mahdi Karim

Researchers studied how this species was faring in the southern Indian city of Bangalore, where air pollution records have been reported as some of the highest in the country. The giant Asian honey bees were observed and collected across four sites in the city over three years. Each had different standards of air pollution.

The number of bees visiting flowers was significantly lower in the most polluted sites, possibly reducing how much plants in these places were pollinated. Bees from these sites died faster after capture, and, like houses in a dirty city, were partly covered in traces of arsenic and lead. They had arrhythmic heartbeats, fewer immune cells, and were more likely to show signs of stress.

There are some caveats to consider, though. For one thing, areas with high pollution might have had fewer flowering plants, meaning bees were less likely to seek them out. Also, the researchers looked at the health of honey bees in parts of the city purely based on different levels of measured pollution. They couldn’t isolate the effect of the pollution with absolute certainty – there may have been hidden factors behind the unhealthy bees they uncovered.

But, crucially, it wasn’t just bees that showed this trend. In a follow-up experiment, the study’s authors placed cages of fruit flies at the same sites. Just like the bees, the flies became coated in pollutants, died quicker where there was more air pollution, and showed higher levels of stress.

The threat posed by pesticides is well known. But if air pollution is also affecting the health of a range of pollinating insects, what does that mean for ecosystems and food production?

Fewer cars, more flowers

Our diets would be severely limited if insects like honey bees were impaired in their pollinating duties, but the threat to entire ecosystems of losing these species is even more grave. Crop plants account for less than 0.1% of all flowering species, yet 85% of flowering plants are pollinated by bees and other species.

Giant Asian honey bees like the ones in Bangalore form large, aggressive colonies that can move between urban, farmed and forest habitats. These journeys expose them to very different levels of pollution, but the colonies of most other types of wild bee species are stationary. They nest in soil, undergrowth or masonry, and individuals travel relatively short distances. The levels of pollution they’re regularly exposed to are unlikely to change very much from one day to the next, and it’s these species that are likely to suffer most if they live in towns or cities where local pollution is high.

Thankfully, there are ways to fix this problem. Replacing cars with clean alternatives like electrified public transport would go a long way to reducing pollution. Creating more urban green spaces with lots of trees and other plants would help filter the air too, while providing new food sources and habitat for bees.

In many parts of the UK, roadside verges have been converted to wildflower meadows in recent years. In doing so, are local authorities inadvertently attracting bees to areas we know may be harmful? We don’t know, but it’s worth pondering. From September 2020, Coventry University is launching a citizen science project with the nation’s beekeepers to map the presence of fine particulate matter in the air around colonies, to begin to unravel what’s happening to honey bees in the UK.

Air pollution is likely to be one part of a complex problem. Bees are sensitive to lots of toxins, but how these interact in the wild is fiendishly difficult to disentangle. We know cocktails of pesticides can cause real damage too. But what happens when bees are exposed to these at the same time as air pollution? We don’t yet know, but answers are urgently needed.

Barbara Smith, Associate Professor of Ecology, Coventry University and Mark Brown, Professor of Evolutionary Ecology & Conservation, Royal Holloway

This article is republished from The Conversation under a Creative Commons license. Read the original article.

38 thoughts on “Air pollution could be making honey bees sick – new study

    • In the US, for most of the country, you need highly sensitive instruments to detect these pollutants. Equipment from 20 or 30 years ago, couldn’t.
      Only a complete ideologue would refer to those kinds of levels as being “laced”.

      As for other countries, they are doing what they can afford to do. If you want them to clean up their environments, then the first thing that has to happen is that we have to allow them to become wealthy as well.

  1. To authors, Prof. Barbara Smith and Prof. Mark Brown, please get back to me when you have something more definitive than “air pollution may be depleting the health” and “if air pollution is also affecting the health of a range of pollinating insects” and “Air pollution is likely to be one part of a complex problem”, all quoted verbatim from your above article.

    I likely won’t still be alive when, if ever, you can do this.

  2. Compared to the days of my youth (60’s-70’s) the air pollution is significantly better now than then. So there should have been no bees flying around then. Given that I have anaphylactic reactions to Bee and Wasp stings, those stings from the bees and trips to the ER were just my imagination according to this research.

  3. This article is short on facts, long on rhetorics. It can be summarized as “researchers observed that unidentified pollutants are bad for bees”.

    • I worked summers in 1970-1971 for a beekeeper with 1100 hives. Even then “Honeybees are threatened!” was the mantra. If we didn’t figure out what was mysteriously killing them, the world would soon starve because honeybees pollinated “90% of our crops!” That was fifty years ago. Some twisted fantasies never die.

      • Yes Brians365,

        There are only bee population records that are spectacularly incomplete and of short duration. What are the normal range of population variability that bees cyclic through, and what is the cause of any of the variations?
        — hint nobody knows!

  4. Air pollution a leading cause of death? Really? Is it even in the top 100 _causes_ of human mortality world wide? Is the list divided to discern between indoor and outdoor pollution? How about between smoking vs non-smoking?
    Granted that it is a health factor, possibly even a directly contributing one, in many deaths and deadly diseases, but air pollution isn’t even a leading cause of death in coal mines.
    But I bet that most dead people have lung damage: correlation is not cause.
    As to bees, for forty years or so we’ve been hearing how delicate European honeybees are — almost entirely where they have been introduced as an invasive species and “kept” by humans for agriculture. Amazingly, wild, Africanized hybrid bees seem to thrive throughout the Americas. Think of it as evolution in action.

  5. I was chatting with a University graduate who was trying to convince me that chemicals made and used by man were all harmful and bad. I looked them in the eye and said “So you’re going to stop taking dihydrogen monoxide then”?
    After a few seconds they said “I’ve never taken that”! to which I pointed at their bottle of water and said “that’s what that is, everything is made of chemicals air is chemicals water is chemicals you are chemicals”
    They didn’t want to talk any more after that, wonder why?
    Not sure what they’d studied but without intelligence learning is redundant.
    I think the authors of this want people to run in circles waving their hands in the air crying “we’re doomed”

    James Bull

  6. What a bunch of absolute BS. However, I would bet that if you asked the average reader of “The Conversation” what they got out of the article they would tell you: “Air pollution is killing honey bees.” But the article said no such thing. It didn’t even offer any proof that air pollution was harmful to bees, even in a couple of the most polluted cities in the world.

    The take-away summary of the article in their own words “… what happens when bees are exposed to … air pollution? We don’t … know.”

    But don’t be surprised when you favorite green snowflake tells you “Scientist say that CO2 is killing honey bees” When scientist don’t and CO2 isn’t air pollution.

  7. My theory’s that might effect low bee populations: Spraying of fields and waters for mosquitoes and black flies.. Roadside and Median spraying along highways and our Interstates. The elimination of “Diverted” acres in farming. Weeds being many flowering plants.

  8. “how air pollution may be depleting the health of honey bees in the wild. These effects may not kill bees outright. But like humans repeatedly going to work under heavy stress or while feeling unwell, the researchers found that air pollution made bees sluggish in their daily activities and could be shortening their lives”

    Could have to do with how Indians harvest honey from wild bee hives.

  9. I remember growing up in southern California in the 1960s and 1970s and being able to see the yellow/brown haze just by looking across my residential street. Air pollution today is next to nothing compared with that.

    • Back then when I was on a Destroyer operating out of San Diego, we would see the pollution before we saw land. It was orange.

  10. The first sentence “Whether it’s exhaust fumes from cars or smoke from power plants, air pollution is an often invisible threat that is a leading cause of death” is classic bait-and-switch fraud. The “leading cause of death” link refers to indoor cooking with smokey open fires in 3rd world countries and doesn’t mention
    fumes from cars or smoke from power plants.

  11. As the US honey bee “crisis” proved, there are lots and lots of pollinators beside the honey bee. Even if honey bees decline, even disappear, the only thing impacted would be a reduction in one of the junk foods (sugar) which is a good thing.

  12. Both the work of Smith & Brown (S&M) and most of the comments (C)points to the camp picture often reflected at WUWT. S&M seem to reside within the carbon scare camp an C on the other side. The major error of S&M is that they immediately home in on burning of orbanic matter and fossile fuel as the cause. This activity is a contributor to stress in many organisms, but far from the only group of detrimental factors. The main and long-term detrimental factor of the global warming scare is as is exemplified in this research presentation and most of the comments, is that the largest damaging factor to all life on earth and in a long term context is overlooked. That is the underegulated and to poorly understood consequences of all new chemicals that man invents, put in production and use, too often so with regretable damage on especially many types of animals. I.e, apart from promoting future habitat loss and starvation due to reduced plant production, the CO2/warming scam drains extreme sums of money and intellectual resources away from a sound management and risk assessment of how we handle man made chemicals. The products are in the five digit numbers and many new chemicals are added to the market at an increasing rate and used and spread widely. Too many do at prent contribute unneccesarly to damage on life of small and big. We know that burning dung is an adaptation to poverty, dense populations with few resources nearby and so on, and otherwise much of an environmental shit in any context due to way it is done now. The debate should move beyond this stage. (NB! I am not against herbicides or pesticides. Was born on a farm, but already as a child I got somewhat concerned when dad came home with dark yellow hands post handling “spraying stuff” for the fields.)

  13. Yea, no way it could be lack of genetic diversity in the honey bee strains sold commercially since the 1950s, that would just be crazy.

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