100% sure that 75% is incorrect

by Luigi Guarino on May 24, 2010

A familiar number was much bandied about during the otherwise wonderful celebration that has been the just-ended Settimana della Biodiversitá here in Rome. We have lost 75% of the diversity of crops during the past century, we were repeatedly told. So I will take this opportunity to repeat from my part that while for all I know this number may indeed be accurate, we have no evidence to that effect. Nobody has counted up all the tomato heirlooms lost in Italy, all the bean landraces lost in Mexico, all the mango varieties lost in India, all the taro clones lost in Papua New Guinea, divided by the number of those things that there used to be, repeated the feat for all other countries in which these crops are grown,1 done the whole thing again for all other crops, taken an overall average and come out with 75%. In fact, as we have said here before, that 75% number is probably an extrapolation from one, probably hardly representative, data point. We should recognize this fact, admit that we don’t know how much crop diversity has been lost overall, quote what numbers there are for genetic erosion with circumspection, and go out and get better numbers.

Footnotes:
  1. Taking care to account for synonyms etc. []

{ 7 comments… read them below or add one }

SusieD May 24, 2010 at 7:13 pm

What a pleasure to read Luigi’s refreshingly rational comments on the use and misuse of numbers! Imagine what miracles could be performed for the hungry world if all the players quoted numbers “with circumspection.”

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Jeremy May 24, 2010 at 9:08 pm

Just out of interest, what miracles does the non-circumspect use of numbers perform for the hungry world? It would be good to have something to compare to.

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André May 28, 2010 at 2:58 pm

Here, in Switzerland, Swissaid has launched a Seeds Caravan in cooperation with some 10 partners.

The inaugural press release says (my translation from German):

Over millennia, world farmers have produced their own seed, SWISSAID Director Caroline Morel recalled. But the world’s seed diversity is now threatened by industrial, and also genetically modified, agriculture.” Result: our food supply rests on an increasingly smaller number of species and varieties – 15 plant and eight animal species supply 90% of world food, whereas 90% of varietal diversity has disappeared from the fields.

The French text is somewhat different (this is just to show that activists still struggle with basic notions):

…increasingly smaller number of varieties – 15 plant varieties and eight animal species supply 90% of world food, whereas 90% of varieties have disappeared from our fields.

With a little effort, genetic erosion will have passed the 100% threshold!

Putting a percentage figure against genetic erosion indeed makes no sense. We neither know the numerator nor the denominator. We do not even know what we are talking about for statistical purposes: names (synonyms)? Truly distinct genetic entities? Genetic entities with unique alleles?

How do we factor in the (sometimes considerable) diversity of recent creation? Should we lump together the agriculturally and/or genetically valuable material and the obsolete – low-yielding, pest or disease susceptible, low-quality, technologically overtaken, etc. – material? How to count the material which subsists in genebanks or breeders’ collections? Etc. etc.

Le Buanec has two interesting paragraphs on this in “Plant breeding and sustainable agriculture – myths and reality.”

If the celebration of the Year of Biodiversity is a celebration and mourning of past century(ies), of course idyllic, agriculture and an occasion to bicker against modern agriculture – with little consideration for the challenges ahead, particularly in terms of conservation of agro-biodiversity – then it will have been a formidable failure. I am afraid, we already know the answer.

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mikkel hoff March 1, 2015 at 12:31 am

I have a question.
“…increasingly smaller number of varieties — 15 plant varieties and eight animal species supply 90% of world food, whereas 90% of varieties have disappeared from our fields.”

Is varieties referring to underlying genetic variation or actual variation in bio or agrodiversity? And i dont ask because i support these numbers – i dont know anything about it.

“Putting a percentage figure against genetic erosion indeed makes no sense. We neither know the numerator nor the denominator. We do not even know what we are talking about for statistical purposes: names (synonyms)? Truly distinct genetic entities? Genetic entities with unique alleles?”

This seems very true. And this is important if we are thinking about preserving genetic material and traits for breeding new varieties.

On the FAO homepage where the 75% is listed, it refers to “plant genetic diversity”, and the reference for this number is impossible to find. But could it not be badly worded, and refer to the overall actual variation in plants used in farming in general (actual biodiversity as opposed to ‘formal’). I am not very proficient in genetics or for that matter in evolution — so perhaps i am completely off.

But this is the question: if the above question isnt completely off — it seems to me that the real question (for the general and underlying biodiversity) would not be about genetic erosion — but about the actual agrobiodiversity (as in actual variation both in genus, species and varieties). And if this is so, then the narrow focus on few plants (and even if the numbers isnt as drastic as the ones mentioned above, and they cant be, can they? A narrowing is definitely taking place) in agriculture would at some point pose a problem — combined with the geographic dissemination of agriculture — for the biodiversity in general. Is there anywhere that i can find some one who have set up a methodology for the measuring of this relationship? Anywhere i can find numbers for this, arguments for when the focus agriculture is to narrow.

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Luigi Guarino March 2, 2015 at 4:17 pm

You could look at this.

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mikkel hoff March 3, 2015 at 1:10 pm

Thanks.

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Luigi Guarino March 3, 2015 at 2:12 pm

Any use?

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