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A reader delves into the one-third question

A while back I wrote Bees pollinate one-third of what? Do we really know? In that post I questioned the frequently repeated statement that “bees pollinate one-third of the human food supply” because I could never discover who calculated this number or how it was calculated.

I wanted to know if it was one-third by weight, volume, calories, dollars, species, or some other measurement. I wanted to know if the one-third was really pollinated by bees, or if that number included all pollinating insects, or if it included animal pollinators as well.

This research is a chore I managed to put off. But this morning I received an impressive review of published literature from an interested reader. You can read her original comments, which are appended to the original post. What she found is interesting. Everyone it seems–even in the peer-reviewed literature–is citing someone else when they publish these numbers. By following the citations backwards, she pinpointed a publication by McGregor (1976) as the source for most of these comments. But no one, so far as she can tell, ever shows calculations.

The suspect publication by S.E. McGregor, “Insect Pollination of Cultivated Crop Plants,” comes closest to providing something of value. But even this document mentions percentages of the human diet without further defining what is meant or how it was calculated. He writes about the number of food species pollinated by insects and about the acres of U.S. soil planted to insect-pollinated crops. From there–in a truly mind-bending leap of faith–he draws conclusions about the percentage of our diet that is derived from insect-pollinated plants.

So it looks like we still don’t have a complete answer, but I wanted to thank Jess for all her efforts at trying to solve this vexing problem . . . and for finding McGregor.

It occurs to me that this conundrum–of one author citing another ad infinitum–is something that we as individuals and societies must be wary of. It is so easy to believe often-cited statistics, advice, or beliefs just because they are often cited. We assume that if everyone says something, it must be true. In this case I am not saying that insects don’t pollinate one-third of the food supply, I just want to know how the calculation was made. Is that asking too much?




Related to this, I thought it was interesting how they handle this “statistic” in this tv show. It’s right around the 2min 30 sec mark if you don’t feel like watching the whole episode. # of species of plants, followed by % of food supply (in terms of volume? dollars? no idea).

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