Einstein’s bees, sound bites and vitamins

By Athayde Tonhasca

If you have been following the news about bees’ decline in the newspapers and social media, you’ve probably come across variations of this quote, attributed to Albert Einstein: “If the bee disappears from the surface of the earth, man would have no more than four years to live.” This insight from one of the greatest scientist who ever lived seems to corroborate another mantra: “one in every three bites of food we eat depends on bees”. So the message from these sound bites is clear and dire: bees’ extinction would lead to food shortages, widespread famine, and ultimately the extinction of mankind.

Considering the seriousness of the matter, we may feel a bit disappointed by Einstein’s vagueness: did he mean the honey bee alone as humanity’s saviour, or the other 20,000 or so known species as well? But don’t blame Einstein for this taxonomical oversight because the quote is a myth: he never said it. Which is not surprising, really; would it be reasonable to expect the man who revolutionized our understanding of space, time, gravity and the universe, to have the time and knowledge to lecture us about bees as well? Probably not. Could the eminent evolutionary biologist Richard Dawkins offer new insights about the Special Theory of Relativity? Probably not. Authority has boundaries, and experts generally know their limitations.

Einstein’s prophecy belongs to the extensive list of fake quotes attributed to him and the likes of Abraham Lincoln, Mark Twain and Winston Churchill. But at least we know that one of every three bites of food we eat depends on bees. Or do we?

The 1 to 3 ratio could be read as the amount of food we eat by weight or by volume, or the proportion of food items in our diet. The latter is the usual interpretation of the quote, which originated from a misinterpretation of a 1976 report by the American Department of Agriculture.

But here are the data. Nearly 90% of the world’s caloric intake comes from rice, maize, millet, barley, sweet potatoes, bananas, wheat, sorghum, rye, potatoes, cassava and coconut. Only the last crop may require some insect pollination. About 60% of global food production comes from crops that do not depend on animal pollination: they are wind-pollinated, self-pollinated or propagated asexually. 

But how about the number of food items? Around three-quarters of the world’s main crops benefit from animal pollination (insects, birds, bats, etc.). But ‘benefit from’ is a far cry from ‘depend on’; pollination is not an all-or-nothing scenario. Crops have diverse degrees of reliance on pollination (see figure), which does not necessarily reflect on yield, but sometimes on product quality or shelf life. Only about 12% of the main crops depend entirely on pollinators to produce the food we consume.

Level of dependence on animal pollination of the main crops produced in 200 countries. Data from Klein et al. 2007. Proc. R. Soc. B 274: 303-313

The ‘1 in 3’ formula ignores meat in our diet. It’s difficult to evaluate the contribution of pollination to meat production considering the range of animal species and production systems. But it is safe to say that the bulk of animal protein originates from plants that don’t need animal pollinators such as grass, maize, and soybean. 

The proportion of animal-pollinated food of course depends on cultural backgrounds, dietary preferences and economic status, but it is not likely to be that great. You can check it for yourself: make a list of non-meat items on your dinner plate and look it up as to whether they are pollination-dependent (you may exclude the pizza and fish & chips dinners).

None of the above undermines the importance of pollination. This ecological service is estimated to account for around 10% of the world’s annual agricultural output; we could expect losses of 5 to 8% in total crop production in the absence of animal pollination. In the EU, 15% of crop production involves pollination, which generates around 31% of the income from crops. These figures are far from inconsequential. And the importance of pollination stretches way beyond yields and income: nearly 90% of the world’s flowering plants require animal pollination, so the whole functioning of the planet is linked to pollinators.

Like any good sound bite, “one in three bites” is memorable and catchy; but as it is often the case with sound bites, it is unclear, inaccurate and simplistic. It also distracts us from pollination’s real contribution to food production, which is the quality of our diet.

Most of the vitamins A, C, and E we need come from animal-pollinated plants such as vegetables, nuts, seeds, and fruits. The same is true for a large portion of vital minerals such as calcium, fluoride and iron. A decline in pollination services would decrease the supplies of these crops, which inevitably would result in higher incidence of diet-related illnesses such as heart diseases, cancer and diabetes. Fewer animal-pollinated fruits and vegetables in our diet would also contribute to the ‘hidden hunger’, which is a form of malnutrition caused by a lack of vitamins and minerals in the diet. Close to 2 billion people worldwide suffer from ‘hidden hunger’; this figure could be brought down by the addition of minerals and vitamins to staple foods, and by protecting pollinators that provide this public health service for free.

The proportion of food production that is dependent on pollination for vitamin A (a) and iron (b) © Chaplin-Kramer et al. 2014. Proc. R. Soc. B 281: 20141799

Pollinators do not contribute significantly to our caloric necessities; the number of bites of food that depend on bees is relatively small. But these few bites are essential for our nutrition and consequently to our health. In a country where 1 in every 4 adults and 1 in every 5 children are estimated to be obese mostly because of poor diet and lack of exercise, reducing the number of bites we eat should be a national priority. But improving the quality of those bites is equally important, with more fruit, vegetables and nuts on our plates: here’s where pollinators make their greatest contribution to our wellbeing.

May the Force be with the bee

By Athayde Tonhasca

If we are asked how a bee finds a flower, we think of smells, colours, shapes and textures. These are important sensory signals, but there is another one whose relevance is just beginning to be understood: electricity.

It has long been known that the platypus, some fish and amphibians, as well as some ants, cockroaches, mosquitoes and fruit flies have the ability to detect external electric forces. However, vertebrates need water as a conductive medium, while most insects respond only to unusually strong electric fields such as those generated by high voltage power lines. Bumble bees however have a sparking story to tell. 

We do not notice it, but our planet is an immense electrical circuit. On a calm day, the air is positively charged, while the ground surface has a negative charge. Now and then the equilibrium of charges is disturbed by lightning bolts or a minor shock from a car door, reminding us we are surrounded by electricity.

The negative charges accumulated on the planet’s surface extend to any object connected to the ground, plants included. So flowers have a slight negative charge in relation to the air around them. As a bee buzzes along in search of food, electrons are stripped off its body by friction with the air, leaving the bee positively charged. When the bee lands on a flower, some of the negatively charged pollen grains stick to the bee, sometimes jumping from the flower even before the bee makes contact. So electrostatic forces are a great aid to pollination.

An electrifying encounter: a positively charged bee approaches a negatively charged flower. Images in the public domain.
Pollen clinging to a sweat bee. © Pixabay.

But flower power reaches shocking levels for the buff-tailed bumble bee (Bombus terrestris), and probably for other bumble bees as well: they are able to sense the weak electric field around a flower. No one knows exactly how they do it, but mechanoreceptive hairs must be involved. These special hairs are innervated at their base, so they detect mechanical stimuli such as air movement and low frequency sounds. Apparently, the flower’s electrical field moves the mechanoreceptive hairs of an approaching bee, similar to the way a rubbed balloon makes your hair stand on end. This hair movement is processed by the bee’s central nervous system and gives information about the shape of the electric field. It is as if the bee ‘sees’ the flower’s electrical aura. 

Bumble bees’ hairs provide thermal insulation, collect pollen and help bees sense air motion, sounds and electricity. ©Kevin Mackenzie, University of Aberdeen. Attribution 4.0 International (CC BY 4.0).

But bumble bees’ capacity to detect electric forces may go beyond recognising flowers’ sizes and shapes: they could use the information to maximise foraging trips. Once a positively charged bee lands, the flower’s electric field changes and remains changed for about two minutes after the bee leaves. Researchers believe that an altered field warns the next bee that the flower is temporarily depleted of nectar; it’s like turning off a ‘we are open’ neon sign. So the next bee may as well buzz off to another flower with sufficient negative charges and a decent volume of nectar. 

Bees and other insects detect ultraviolet and polarized light, and use magnetic fields for navigation. Sensing electricity is one more way their world is experienced radically differently from ours.