One thing we have learnt this week – crop diversity

seedlingsI’ve just found a very interesting paper on crop diversity published this year in the journal PNAS.  The authors have assessed the trends in crop diversity over the last 50 years and what they have found is informative and worrying.

The first trend is towards energy dense foodstuffs such as those rich in animal fats, sugars and plant oils with a decline in consumption of pulses, vegetables and traditional crops that fall into the categories of those high in sugars and plant oils. This has health implications with heart disease, cancer and diabetes all on the increase.  All these are diet related, at least in part.

The second trend in crop diversity was that of homogenisation, i.e. our diet worldwide is getting increasingly similar and less diverse.  We are all increasingly eating the “Western diet”.  This also has health implications.

The final main finding is that particular amongst the main commodity crops the diversity is also falling, in other words we are growing a few varieties of for example wheat or maize.  In the 1970’s the US maize crop failed one year since it was all one variety that was disease susceptible.  Currently the great majorities of bananas sold are the Cavendish variety, this is being eliminated by a fungal disease to which it has no immunity.  One of the hidden problems of GM is that it will tend to reduce crop diversity, since GM crops are expensive to develop and usually just cover one desired trait.

Does this fall in crop diversity matter?  I think it does.  Climate change is causing new diseases to appear and spread.  Some old varieties may have disease immunity or drought tolerance etc.  We need to eat less protein and sugars for both health and sustainability reasons so more crop diversity could be a good thing for these reasons as well.  We may need to go back to old varieties for other sustainability reasons.  I read recently that modern wheat is completely dependent on chemical fertilisers which are unsustainable in the long term.

This is a well written paper, although some of the graphs are a little incomprehensible.  The authors admit to shortfall in raw data such as that on what people grow in gardens.  This last point is important, you can help by growing old varieties yourself, collecting seeds and sharing.  I have planted old varieties of apples and grow a diverse range of veg, although ironically some of these are new varieties.  I also increasingly buy spelt flour, primarily because it makes lovely bread, but it should also encourage the cultivation of an ancient form of wheat.  Kew gardens are involved in a project to collect seeds in case of climate disaster.  Links to details about that and the PNAS paper are here.


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