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.

A healthy diet for fussy eaters

By Athayde Tonhasca

Pollen, the fertilizing agent that carries the male gametes (reproductive cells) of flowering plants and grasses, is packed with protein, starch, sugars, fats, vitamins, and inorganic salts: carotenoids and flavonoids add the colouring. This rich resource wouldn’t go untapped by many insects and mites. Among them, bees are the ultimate palynivores (pollen eaters).

To us humans, one pollen grain is indistinguishable from the next: it’s that granular yellow stuff that may cause seasonal allergies such as hay fever. But pollen of different plant species comprises a smorgasbord of chemicals. Protein, by far the most important nutrient as the source of vital amino acids, ranges from 2 to 60% of pollen dry mass. The composition and amount of other essential nutrients vary as well. Some pollen contains secondary metabolites such as alkaloids and glycosides, which are harmful to some bees: buttercups and related species (Ranunculus spp.) for example are toxic to honey bees. Pollen grains of some plant families are coated with a sticky substance called pollenkitt, which probably helps pollination. But just as some people can’t digest lactose, some bees can’t digest pollenkitt.

Miscellaneous pollen grains © Dartmouth College Electron Microscope Facility, Wikipedia Creative Commons

Bees have adapted to the range of pollen quality by adopting diversified diets: most species are polylectic, that is, they collect pollen from various unrelated plants (as opposed to oligolectic species, which specialize on a few related plants). By taking pollen from many sources, bees get a balanced diet and reduce the relative intake of harmful chemicals. When polylectic bees are fed pollen from a single source, they often fail to reproduce or die. The need for nutritional diversity has deep implications for bee conservation. 

Agri-environment programmes throughout Europe have promoted the creation of flower-rich habitats to reduce the impact of agriculture intensification on pollinators. Field margins and other non-crop areas are planted with seed mixtures, and the practice has made a difference: bumble bee declines have slowed or sometimes reversed in recent decades. As a bonus, honey bees and butterflies have benefited as well. However, most solitary bees (which make up about 90% of the approximately 250 species of bees in UK) have been unintentionally left out.

Two of our solitary bees: a miner bee © Pauline Smith, and a leafcutter bee © Saxifraga – Pieter van Breugel

It turns out that seed mixtures comprise a high proportion of legumes (family Fabaceae) such as red clover, white clover and vetch. These plants are good for bumble bees, but are not the best or not suitable at all for many solitary bees. Most species get their pollen from plants such as smooth hawk’s-beard (Crepis capillaris)scentless mayweed(Tripleurospermum inodorum), field bindweed (Convolvulus arvensis), rough chervil (Chaerophyllum temulum), meadow crane’s-bill (Geranium pratense) and dandelions (Taraxacum agg.). Species from the families Asteraceae (daisies, marigold, snakeroot, tansy, thistles) and Apiaceae (cow parsley, wild carrot, ground elder) are also important. 

Weeds or food for pollinators? Smooth hawk’s-beard (L) © Michael Becker, Wikipedia Creative Commons, and wild mustard (R) © Hectonichus, Wikipedia Creative Commons.

These plants grow naturally in and around arable fields, but some of them are not welcomed by farmers because of their invasiveness. Wild mustard (Sinapsis arvensis) and wild rose (Rosa canina) for example are excellent sources of pollen for solitary bees, but the first is a serious weed of oilseed rape fields and other crops, and the latter is a climbing shrub, not suitable for field margin management. 

The inclusion of weeds in seed mixtures may not be an option, but a more tolerant attitude towards them would be beneficial and safe. A wild plant does not become a weed until it starts competing with crops, and this threshold may take a while – or it may never be reached. The same principle applies to our gardens: we don’t need to kill weeds willy-nilly for questionable aesthetic reasons.

As in so many areas of conservation, the answer lies in finding a middle ground. We need to cultivate an appreciation for wildness over manicured fields and gardens because just as a varied diet is best for human health, a diversified flora represents an essential buffet for bees and other pollinators.