Air Pollution Could Be Shortening the Lives of Honeybees in the Wild
Wed, April 21, 2021

Air Pollution Could Be Shortening the Lives of Honeybees in the Wild


If air pollution is dangerous to people’s health, it just makes sense that it is harmful to other animals too. A 3-year study in India, for instance, found that bees can feel the sting of air pollution more accurately than humans do.

Importance of pollinators for India’s food security

Their study, which appeared in the Proceedings of the National Academy of Sciences of the United States of America, highlights that India is the world’s second-most populous country and is the world’s largest fruit producer. Pollinators are therefore important for their food security but 9 of the world’s 10 most polluted cities are also found in India. So far, the impact of air pollution on animal systems and plants is largely unknown so the researchers conducted a multilayer study in Bangalore to find the connection between the Giant Asian honey bee Apis dorsata and the effects of air pollution in India.

Upon sampling the Giant Asian honeybees, which are a major Indian pollinator, at locations with different air pollution levels in Bangalore, authors noticed the significant connection between increased respirable suspended particulate matter (RSPM) deposition and the changes in bee flower visitation, heart rate, expressions of genes related to immunity, stress, and lipid metabolism, hemocyte levels, and their survival.

Air pollution making bees sluggish

The effects of air pollution may not kill the honeybees outright. However, just like how humans repeatedly working while feeling unwell or feeling heavy stress, air pollution also made honeybees sluggish in their everyday activities. Thus, it is shortening their lives in the wild.

Giant Asian honey bees are not like European honey as they regularly resist other animals and humans to harvest their honey. This is why they are predominantly found in the wild. Within a year, their colonies can migrate over hundreds of kilometers, pollinating a wide range of crops and wild plants across India.

The authors observed the honeybees over three years while they were exposed to different standards of air pollution. Results also show that the number of bees visiting flowers was lower in the most polluted areas. It is, therefore, possible that plants in these places are less pollinated. Honeybees from the most polluted sites also died faster after capture and were partly covered in traces of lead and arsenic.



Bees in the most polluted sites have fewer immune cells

Geetha G. Thimmegowda from the National Centre for Biological Sciences of Tata Institute of Fundamental Research in Bangalore and colleagues wrote that bees in the most polluted sites also have fewer immune cells, had arrhythmic heartbeats (problem with the rate or rhythm of the heartbeat), and were more likely to show signs of stress.

Coventry University's Associate Professor of Ecology Barbara Smith and Royal Holloway's Professor of Evolutionary Ecology & Conservation Mark Brown, who were both not involved in the study, shares some cautions though. They said that areas sites with high air pollution may have fewer flowering plants so bees were less likely to seek these places. Furthermore, the Indian researchers looked at the health of the honeybees based on various levels of air pollution. There was no isolation of the effect of air pollution with absolute certainty. There may be hidden factors why these bees were unhealthy, Smith and Brown added.

But to prove the threat posed by air pollution on honeybees, the Indian researchers did a follow-up study by placing cages of fruit flies in the same places. The result shows that the flies were also covered in pollutants. They also showed higher levels of stress and died faster in sites where there was more air pollution. Aside from air pollution, pesticides could also be affecting the health of pollinating insects.

Cities with the worst air quality in the world

IQAir AirVisual's 2019 World Air Quality Report shows that some of the world’s cities with the worst air pollution are in India. IQAir is a global air quality and information tech company, which gathers data from the on the ground monitoring stations that measure the levels of fine particles PM 2.5. Exposure to said pollutants has been linked to heart and lung disorders and can impair immune and cognitive functions.

Ghaziabad, a largely suburban district of Uttar Pradesh state in northern India, is ranked as the world’s most polluted city. It has an average PM 2.5 concentration measurement of 110.2 last year, nine times more the level which the US EPA considers as healthy. It is followed by Hotan, China (110.1 PM 2.3 concentration), Gujranwala, Pakistan (105.3), Faisalabad, Pakistan (104.6), Delhi, India (98.6), Noida, India (97.7), Gurugram, India (93.1), Raiwind, Pakistan (92.2), Greater Noida, India (91.3), and Bandhwari, India (90.5).

The World Health Organization shares that about 7 million premature deaths a year are caused by air pollution and as a result of increased mortality from respiratory infections, cancers, and cardiovascular disease.



India’s honey production volume

Meanwhile, Statista shares that the production of honey across India in the financial year 2015 amounted to 4,800 metric tons. The numbers gradually decline in the following financial year: 2016 (4,100 metric tons), 2017 (3,700), 2018 (4,000), and 2020 (4,000)

Thimmegowda and colleagues from India said that intense agriculture, poor emission enforcement, and control, and rapid urbanization coupled with a dependence on poorly maintained and old vehicles in the past century have led to a great increase in air pollution not only in India but the developing world. Previous studies have also acknowledged the effect of air pollution on insects’ olfactory behavior and their populations. Effects could include indirect decline because of disequilibria (loss or lack of stability) and direct toxicity to their population.

For insects, air pollution impact then strongly, especially their olfactory-guided behavior since they use such in almost every aspect of their biology from searching host sites, mates, food to avoiding predators. For instance, air pollinators use chemical signals to locate flowers and other organisms but this may be hindered or destroyed with pollutants. The smoke has also been shown to reduce bees’ alarm pheromone detection.

If insects like honeybees are impaired in their pollinating duties, it would create rippling effects on the ecosystems. We, humans, may also lose the plants that bees pollinate and our food would be limited.