Category: Nutrition

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Joining the dots on food plant diversity

We have access to more kinds of food plants, yet the world’s diets and production systems have never been more alike. That is the paradox at the heart of Food plant diversity in a rapidly changing world, an unusually broad review by Colin Khoury (very much friend of the blog) and colleagues. It has all the latest data, but it also does several other things that make it more than a conventional state-of-the-art paper.

For one, it brings together diversity at several levels that are too often discussed separately: species, varieties and genes, of course, but also the diversity of diets, farming systems, foodways and the knowledge associated with them. It traces the movement of cultivated food plants over the past 12,000 years alongside the much more recent trend towards homogenisation. The result is the weird world we live in today: more kinds of crops available globally, but less difference between what people in different places eat.

Colin and friends also take a hard look at what we don’t know. We have surprisingly little evidence for how much food-plant diversity has actually been lost, how vulnerable today’s production systems are because of increasing uniformity, or what is happening to less visible forms of diversity, such as nutritional and chemical variation. The authors call for better monitoring, including an early-warning system for crop vulnerability. Now where have I heard that before?

And the paper connects the dots between conservation approaches that all too often live in isolation: genebanks, botanic gardens, community seed banks, on-farm initiatives, protected areas, breeding programmes and markets. Genebanks are all well and good, but diversity also needs to keep going in fields, landscapes, cuisines and communities. Again, not particularly new, but it’s good to have it repeated, brought up to date, and placed in the broadest possible context.

A couple of those dots are discussed in more detail in a companion opinion paper, Enhance food plant diversity conservation and use through greater coordination between genebanks and botanic gardens, which asks what might become possible if two of the world’s major plant conservation communities worked a bit more closely together. Which must be possible because they are nicely complementary, so neither should fear the other as a competitor.

The review paper maps the problem. The opinion piece explores a possible route towards a more joined-up conservation system. Which leaves us with its own small paradox: conserving food plant diversity requires flattening some of the differences within a remarkably diverse conservation community. Happy Crop Diversity Day 2026.

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Where have all the nutrients gone?

The “nutrient collapse” story has been doing the rounds for years, and we’ve been picking at it on the blog for almost as long.

Back in 2009, Jeremy looked at evidence that older crop varieties could contain more minerals, protein and other nutrients than newer ones, and discussed various possible reasons, including the intriguing possibility of a “genetic dilution” effect as breeders selected for yield.

By 2012, we were stressing that the evidence was more complicated than the headlines suggested, and in 2019 we linked to the latest critical review of the evidence by Robin Marles of the Bureau of Nutritional Sciences in Canada.

Now the latest episode of the BBC’s indispensable More or Less podcast asks again whether carrots are becoming less nutritious, prompted by a listener who clearly hasn’t been following our blog, and turns to Dr Marles, now retired, for the answer. Which hasn’t really changed much.

The bottom line is that breeding for yield and other commercially important traits can change the balance of what ends up in the harvest, and that we have historically been much better at measuring tonnes per hectare than what is actually in those tonnes.

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Brainfood: Opportunity crops, meet your constraints

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Nibbles: Frafra, Seed multiplication, Quality seeds, Balearic genebank, Indigenous trees double, Bruno cart, Belgian wild yeast

  1. Frafra potato is having a moment: an indigenous West African tuber, adored locally and mostly ignored by science, out looking for its big commercial break.
  2. Speaking of breakthroughs, this bus driver found his own, swapping the wheel for seed multiplication and turning five acres into a livelihood, proof that sometimes the missing link in a seed system is just someone willing to do the unglamorous middle bit well.
  3. Which is, per Farming First, precisely Africa’s problem at scale: only 2.5% of smallholder seed in Sub-Saharan Africa comes from formal seed companies, so a few million more bus-driver-style multipliers wouldn’t hurt.
  4. Meanwhile in the Balearics, the opposite direction of travel: the local seed bank is expanding to rescue tomatoes, onions and broad beans, and is looking for farmers willing to take them back.
  5. Indigenous fruit trees in Malawi turn out to fight malnutrition and biodiversity loss at once. Happy coincidence?
  6. Getting those trees into the ground well needs the same unglamorous groundwork as any good crop seed system: a Mongabay commentary argues that restoration campaigns skipping Indigenous and local seed knowledge are optimising for trees planted, not trees that survive.
  7. And once you’ve got the saplings in the ground, you might want to monitor how they’re doing: enter Bruno, a pushcart rigged with mobile phones that can collect field data. And not just for breeders.
  8. Finally, proof that not all genetic-resource hunting needs a genebank: Brussels brewers are getting people to comb the city for wild yeast, because the raw materials for a proper lambic turns is hanging around in urban trees.
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What is maize good for?

Two pieces of work on maize I recently came across are unconnected as to aim and place, but nevertheless make for an interesting combined story. One asks how far maize yield can actually be pushed by the environment; the other, how far we should define its success by yield anyway.

The first study is a systematic analysis of more than 14,000 yield observations across sub-Saharan Africa. It finds that maize generally produces more grain than pearl millet, even in relatively dry environments. That complicates the familiar story that the traditional, hardy millet simply “beats” the relative newcomer, more pernickety maize in marginal conditions. And you know how much we love complicating a conventional story here.

But, heaping complication upon complication, there is a catch: maize’s performance is much less consistent. Its high yields are associated in part with hybrids and the input packages that accompany them, whereas pearl millet produces yields that are lower, sure, but also more stable. And grain weight leaves quite a lot out anyway: millet brings higher levels of iron, zinc and protein. The authors therefore argue that comparing cereal crops by yield alone can obscure their actual advantage to farmers, under their own conditions. That’s been a recurrent theme with us here, actually, come to think of it.

The Philippine experience described in the second study makes a similar point from the farmer’s side of the equation. In Laguna, farmers evaluating maize varieties did not rank them simply by how many tonnes they produced. They cared about taste, culinary uses, familiarity, nutritional value, market prospects and climate resilience as well as yield. The authors recommend involving farmers in local testing and breeding efforts, rather than treating them as merely the final recipients of fancy new varieties.

Put together, the two stories suggest a useful way of thinking about the potential, and the limits, of maize — and indeed any other crop for that matter. Maize is remarkably productive and adaptable, and the evidence does not support writing it off completely in dry conditions. But its apparent superiority depends strongly on what we measure, where we grow it, and what we put into the system.

A tonne of maize produced with expensive hybrid seed and inputs is not necessarily a better outcome than a more modest but more dependable harvest of millet; nor is a variety that comes out on top in a yield trial necessarily the variety a farmer most wants to eat, sell or grow next year.

Maize can do a great deal, but its real potential emerges only when yield is considered alongside stability, inputs, nutrition, markets and, ultimately, what the people growing and consuming it really want.

Sometimes, in some places, even maize can be an opportunity crop. Other times, not so much. And that goes for millet too.