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Pollinator dependent crops – from waking up to good nutrition

Pollinator dependent crops – from waking up to good nutrition

I don’t know about you, but I definitely need coffee in the morning. To start the day right, it’s absolutely an essential. But besides of my attempts to get a productive human in the mornings, coffee is pollinator dependent. And here we start the more relevant topic: though coffee is a huge economic factor, there are huge gaps in the knowledge of its pollinators. In a review on coffee pollination, Ngo et al. summarize the pollinators observed in different countries.

Coffee – modestly pollinator dependent…

From all the insects observed on coffee flowers, bees make the main part. Apparently, coffee pollination is under-studied in its native area: no African country appears in the table listing coffee pollinators. Except Indonesia, it was all about Latin America (Brazil, Panamá, Costa Rica etc.). Western Honey Bees, Apis mellifera, appear in almost every study as one of the major pollinators for the Latin American countries. Other important species are stingless bees. In Indonesia, the native Apis species (A. nigrocincta, A. dorsata, A. cerana) take the job, together with other, as far as I see mostly social bee species.

Together with the bees, there were some mentions of other insects: flies, moths, wasps and ants. However, as stated in the review, the role of these insects isn’t completely clear. In addition, coffee is only modestly pollinator dependent: on average it is 50% self-pollinated. However, for making up the 2016 coffee production, 22 trillion pollinator visits were necessary. Jeff Ollerton calculated this for his review on pollinator diversity. Considering the huge economic factor coffee is, I wonder why there are still so huge knowledge gaps. Pollination ecologist should be the most wanted people for coffee growers…

I also wonder if this dominance of social bees really represents the most efficient pollinators… The insects considered “major pollinators” were those with more than 5% visiting frequency. Pollination, i.e. result of the visit, was not determined. It is little surprising that social bees make the most frequent flower visitors – they are social, i.e. present in huge numbers. The authors of the review state this themselves, but it always surprises me how little we know about things, even if they matter to us.

… together with highly dependent chocolate

Coffee pairs very good with chocolate. A piece of dark chocolate melting in your mouth while you drink a good espresso… one of the little pleasures. Chocolate comes from cocoa, a plant that is highly pollinator dependent. Here we definitely move away from the bees. The pollinators responsible for my favourite after lunch treat are midges. To be precise: biting midges. Sounds not very attractive to me, especially because they do their name honour, apparently. The females of these insects bite and suck blood, which makes me itch even only writing this. “But”, as Erica McAlister says, “… without these minute, often rage-inducing flies, many people would consider that life is no longer worth living.”

In addition, the cocoa plant isn’t an easy case regarding pollination. It cannot self-pollinate itself, like coffee, so it absolutely needs the biting midges. And here the problems begin: cocoa plants naturally grow in forests, together with other trees. These create the damp and shady conditions these midges need. In cultivation, cocoa plants often grow without this protection, the midges don’t find the right conditions anymore. In consequence, there are less of these essential pollinators and the cocoa bean production is… well, modest. A solution for this may come from Australia: Samantha Forbes added organic matter (I assume the kind of litter you find in tropical forests) to the soils of cocoa plantations. This increased the pollination significantly.

Healthy nutrition depends on pollination

But it’s not only about the pleasure of coffee and chocolate, not only the yield and market quality of the crops. Pollinator dependent crops are sources for many micronutrients, i.e. vitamins and minerals. These are essential for our health. For instance, 50% of the vitamin A sources from plants in Southeast Asia need pollination. An example for this is Mango, which is highly pollinator dependent. In these regions however, the production of vitamin A rich crops doesn’t meet the needs of the population, as this paper explains. Vitamin A deficiency is a serious thing, about 250-500,000 children go blind every year because of it and many die. Pollination, therefore, gets also a public health issue, especially in the poor regions of this world.

Apart from the risk of malnutrition in developing countries, the nutrients in fruit and vegetables are also important for the nutrition in the food abundant countries. And by the way: you may have enough to eat but still can be deficient on some nutrients. When you eat a healthy diet, a large part of it will come from crops that to some extent depend on pollinators. Apples, cherries, peaches and many other fruit do. Vegetables often at least for seed production.

As spring is approaching, let’s take strawberries as an example. Strawberries can self-pollinate, but with insects the overall yield and also the fruit quality and shelf-life increases. I would classify strawberry flowers as “bee flowers”, but according to a very recent paper, hoverflies also play a big role. A mix of different species worked best in pollination cages, which were used to exclude pollinators other than hoverflies. In the experiments, they boosted the yield by over 70%, which is amazing. (See the specifications in the author’s comment below this post.)

Pollinator diversity

This last finding brings me back to the post about pollinator diversity some weeks ago: we need the whole diversity of pollinators to get the best quality, highly nutritious crops. Some crops may depend on single pollinators like cocoa or figs, but others rely on a “mix of species”. All pollinators have different life-histories and need different conditions. They work as a “team”. Therefore, in some years it may be the hoverflies that do the best strawberry pollination, in others it may be the bees. We just have to make sure that all of them have some room to live also outside the crop. Which may be the largest challenge… but this is something to address in a future series coming in June, about bees and agriculture.

Meanwhile, remember that it’s the diversity that gives the best results and eat your fruit and veggies.

2 Comments

  1. Dylan Hodgkiss

    Excellent blog post and thank you very much for including a link to our JPE paper on hoverfly pollination of commercial strawberry! The only thing I would like to point out is that our study actually didn’t test whether a mix of hoverfly species performed better at pollinating strawberries than individual species of hoverfly.

    Though mixed assemblages of hoverflies increased yields by 70% over pollination cages without insects, individual species (Episyrphus balteatus and Eupeodes latifasciatus) both increased yields by over 90% when compared to plants that did not receive insect visits. However, these results were obtained in different years, so they’re not directly comparable. For example, it’s possible that the pollination cages without insects performed worse in the year when we tested individual species of hoverfly. Nevertheless, we found that hoverflies, specifically hoverflies with aphid-eating larvae, were effective strawberry pollinators.

  2. beesafe

    Thank you for your feedback and specification! I just picked out the point that helped my argument, so sorry if I was too imprecise.

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