Did you ever look at the blades of a fan and notice how the leading edges gather crud from the air? It’s gross, and whenever I see it, I imagine breathing all that stuff.
It turns out that honey bees also have a problem with dirty air. A new paper appeared earlier this month in the Proceedings of the National Academy of Science that shows insects, specifically the giant Asian honey bee, Apis dorsata, and the common fruit fly, Drosophila melanogaster, can suffer severe health problems due to air pollution.
Stress, heavy metals, and poor health
The paper, titled “A field-based quantitative analysis of sublethal effects of air pollution on pollinators” compared individuals from extremely polluted areas of India with individuals from less polluted areas over a three-year period. The differences were stark.
The lead author, Geetha Thimmegowda, and her associates examined the bodies of over 1800 bees. Of one bee in particular she said, “Its body looked like a war zone.” In addition, many bees had wing edges “crusted with dirt” and others were “covered with all sorts of crud and particles.”
When the wing deposits were examined, the researchers found toxic heavy metals, including arsenic, lead, and tungsten, and eighty percent of the heavily-coated bees died within one day of capture. Postmortem examinations revealed that the bees in the most polluted areas showed signs of poor cardiac health, stress, and compromised immune systems along with damaged antennae.
Bees from the less polluted areas were able to visit up to twice as many flowers per day as their polluted kin and they lived longer. The fruit flies yielded similar results, including indications of stress and shorter lifespans.
Bees lose the ability to navigate
India has a major problem with air pollution and is home to 9 of the top 10 most polluted cities in the world. But previous research in other countries has shown that car exhaust interferes with honey bee navigation by masking scent cues, which makes finding flowers difficult. The current research adds another layer of complexity, showing that pollution can damage a bee’s overall health as well as its ability to navigate.
The authors stress that these are sublethal effects. In other words, they do not kill the bee outright but shorten its life and interfere with its ability to function normally.
Death by a thousand cuts
Those of us who live in less polluted environments should not be complacent. Many things about our modern world impair our pollinators, and it’s impossible to know how much each factor contributes. Even if things like air pollution contribute only small amounts to colony demise, when you start adding them together, you can see that “just a little bit” of something might be enough to tip a colony over the edge.
Take an average colony of bees. A certain percentage might die of exposure, predation, or bad genetics. More might die of pesticides, parasites, and pathogens. You can also add habitat loss and fragmentation, loss of forage due to invasive weeds, or the chance of getting diced by a lawnmower. And now air pollution. How many will that kill? We don’t know, but we can see the news is not good.
At some point, not enough bees remain to sustain the colony. Lots of people say, “My colony just died. It seemed fine, I treated for mites, I supplemented its food, I checked for disease, but it still died. What did I do wrong?”
When I hear that, I always wonder. Maybe the beekeeper did nothing wrong. Maybe a three percent loss here, and a five percent loss there, and a seven percent loss later on combined with all the other misadventures was enough to make it fail. I don’t believe there is always one big overriding cause of colony death. Many times it could simply be death by a thousand cuts.
The biggest job of all
We still need to do everything we can to help our bees. We need to monitor, treat when necessary, and give our colonies a leg up if they need it.
Sometimes, though, things spiral out of our control. We must remember that the world our bees are forced to live in is not the one they evolved in. The best thing we can do for all living things is to take giant steps toward saving our environment and our planet. This is job one for all of us.
Honey Bee Suite