I was recently reminded of a post I wrote in 2006, and thought to myself that it could have been written yesterday. The trigger for this memory was a long piece in the New York Times that appeared more or less yesterday.
The subject is superweeds; that is, weeds resistant to one or more herbicides. In 2006, I was writing about waterhemp (Amaranthus tuberculatus), which had recently been shown to have developed resistance to an entire class of weedkillers. The thrust of it was that resistance involved mutations in two separate genes, taken together a one in a billion billion (1,000,000,000,000,000,000) chance. But it happened. Agriculture selects improbable events.
The NYT article was about another amaranth, Palmer amaranth (A. palmeri). The thrust of it was that Palmer amaranth is now resistant to at least six different classes of herbicide.1 In 2006 it was resistant only to glyphosate. That leaves farmers with almost no options to control Palmer amaranth, and control it they must.
In 2008, researchers scattered 20,000 seeds of glyphosate-resistant Palmer amaranth into a 1 metre diameter circle in the middle of four different cotton fields that had no history of Palmer amaranth. The experimental sowing was intended to represent survival and maturity in the field of a single resistant female Palmer amaranth plant.2 After that, they managed the glyphosate-resistant cotton as per recommendations, spraying to control the weeds.
One year later, in one of the fields, Palmer amaranth had moved 114 m from the original site in one of the fields. Two years later, the weed had spread to the boundaries of all the fields and covered 20% of the field area. “Three years after the introduction (2010), Palmer amaranth infested 95 to 100% of the area in all fields, resulting in complete crop loss since it was impossible to harvest the crop.”
That paper goes on to discuss some possible management options, suggesting a “zero-tolerance threshold” to eradicate every weed. I doubt anyone even tried. For its part Monsanto, which had developed glyphosate-resistant seeds, worked to stack resistance to another weedkiller — dicamba — into its genetically engineered seeds, a pointless exercise. As the NYT reports, “The agribusiness giant took a decade to develop that product line. The weeds caught up in five years.”
A squandered resource
The evolution of resistance to some life-threatening challenge is axiomatic in biology and it doesn’t matter whether the threat is an antibiotic, a herbicide, fungicide or insecticide, or even a predator. Anything that gives an organism even the slightest competitive edge in its ability to reproduce will in the end be selected. The problem is certainly not unique to genetically modified organisms. In the mid 1990s, wild oats resistant to three and four classes of weedkiller appeared on the Canadian prairies. Agriculture Canada blamed farmers who ignored advice to rotate crops and herbicides.3 But genetic engineering has exacerbated the problem many times over by giving natural selection so many more opportunities to do its inexorable thing.
Antimicrobial resistance is, belatedly, gaining a little recognition. Herbicide resistance might just be heading in the same direction, if the New York Times is taking an interest. These problems are, to some extent, a manifestation of a mismanaged commons; to begin with, using the stuff confers a benefit on the individual, but as everyone does so, everyone begins to suffer. In agriculture, they’re also a reflection on efficiency at any cost. Good weed control means good preparation of the soilbed, physical weeding three or four times during the life of the crop and other practices that take time and, therefor, money. How much easier to pay over the odds for seeds, buy weedkillers from the people who lent you the seeds, spray and pray. The same goes for antibiotics as growth promotors. Shave a fraction of a percent off feed costs and multiply that across millions of animals and you create a powerful incentive to abuse antibiotics. And just as it isn’t genetic engineering per se that creates problems of resistance, it isn’t agriculture per se that makes the improbable certain. It is the way agriculture is conducted.
What to do
Scientists have offered lots of advice on how to minimise the problems of resistance, some of which have even made it into policy. Just recently, the Food and Drug Administration tightened up a bit on its Guidance for Industry on the use of antibiotics on farms. From June 2023, a veterinary prescription will be needed for all antibiotics. I’m sure no veterinarians will be tempted to issue prescriptions that might not be absolutely necessary.
As it happens, organic farmers don’t use chemical herbicides on their crops, and superweeds are much less prevalent on organic farms. An excellent long article in Civil Eats uses one organic farmer’s fight against glyphosate-resistant giant ragweed as a jumping off point for a thorough discussion of the difficulties of controlling weeds in the oversimplified farm systems of the US corn belt. The key is hybrid rye, which overwinters and helps to smother ragweed as it emerges in the spring. Control can be achieved, but as the article makes clear, there are lots of obstacles, not least the difficulty of finding uses for hybrid rye. Longer rotations, increased diversity, more hands-on management, local cooperation: all are necessary, and all go against the grain for the majority of today’s corn belt farmers. Nevertheless, something is going to have to happen, and another technical fix is unlikely to be any kind of solution.
If you can’t beat them …
There is an additional approach, at least for Palmer amaranth. Its leaves, stems and, especially, seeds are edible, delicious, and highly nutritious (as they are for many amaranths). In theory, one could, perhaps, turn the noxious weed into a nutritious addition to the diet. And even though it is glyphosate resistant (not to mention the other five weedkiller classes), it come by that resistance natural, rather than through meddlesome genetic engineering, so there couldn’t possibly be any objection to eating it.
The two articles, in the New York Times and Civil Eats, are well worth reading in their entirety.
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Waterhemp, too, is resistant to the same six. ↩
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The NYT said “researchers planted a single Roundup-resistant Palmer amaranth plant”, which is not exactly correct, but no matter. ↩
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Nothing New under the Sun, ref. 6. ↩
The Economist on investing in adapting agriculture
A much wider range of adaptations will be needed if food is to remain as copious, varied and affordable as it is today. These will include efforts to help crops withstand warmer temperatures, for example through clever crop breeding, advances in irrigation and protection against severe weather. Rich and poor countries alike should also make it a priority to reduce the amount of food that is wasted (the UN’s Food and Agriculture Organisation guesses that more than one-third is squandered). The alternative will be a world that is hungrier and more unequal than it is at present—and than it might have been.
That’s from The Economist‘s analysis last week of projected shifts in the distribution of crops around the world as a result of climate change. Needless to say, genetic diversity will be needed to do all those good things. Investors read The Economist, right?
Investing in biodiversity
What do investors think of biodiversity? Well, a new report from Credit Suisse and Responsible Investor says that they’re increasingly interested, but that they are not (yet) putting their money where their mouths are. The reason?
Investors are struggling to identify and consider biodiversity-linked investment opportunities. Biodiversity needs to be made more digestible and measurable for investor concerns to translate into investment action…
More digestible? Now there’s an opportunity for agricultural biodiversity at least.
The challenge of protecting wildlife and nature has fallen behind many other sustainability issues for investors and governments alike. Part of the explanation likely lies in the complexity of biodiversity and its loss. “Diversity is the opposite of investors’ desire for standardisation and comparability of things,” says Piet Klop, Senior Advisor Responsible Investment, PGGM. “Biodiversity is challenging because it really is the anti-commodity.”
Ah yes, functioning ecosystems and food as anti-commodities. Can we not muster some decent arguments against this pernicious view?
Brainfood: Pollinators double, C4 grasses, Pre-breeding, Lupins resources, New wild coffees, Refugee deforestation, Tuber niches, Sampling strategy, Infection risk, Levant Bronze & Iron Age
- A global-scale expert assessment of drivers and risks associated with pollinator decline. “Key findings: 1) risks to human well-being from pollinator decline are higher in the Global South; 2) there is a clear lack of knowledge about pollinator decline in Africa; 3) loss of managed pollinators (e.g. honey bees) is only a serious risk to people in North America.” That’s according to the main author Dr Lynn Dicks on Twitter.
- Agrochemicals interact synergistically to increase bee mortality. Stress on pollinators is more than the sum of its parts.
- Evolutionary innovations driving abiotic stress tolerance in C4 grasses and cereals. Major C4 crops need more stress.
- Deep scoping: a breeding strategy to preserve, reintroduce and exploit genetic variation. You may not need a separate pre-breeding programme to introduce new diversity into your breeding programme without wrecking it.
- Genomic resources for lupins are coming of age. Maybe we could have a pre-breeding programme now?
- Six new species of coffee (Coffea) from northern Madagascar. Including 4 really narrow endemics. I wonder what they taste like. Start evaluation and pre-breeding?
- Refugee camps and deforestation in Sub-Saharan Africa. Much, much less of an impact that you’d think.
- Suitability of root, tuber, and banana crops in Central Africa can be favoured under future climates. More than you’d have thought.
- Proportional sampling strategy often captures more genetic diversity when population sizes vary. Sample more than you normally would from bigger populations of rare wild species.
- Plant pathogen infection risk tracks global crop yields under climate change. Where yields go up, fungal/oomycete infection risk goes up; where yields go down, so does infection risk. Assemblages will change especially in temperate regions.
- Developments in Subsistence Practices from the Early Bronze Age through the Iron Age in the Southern Levant. From pigs, wild animals and emmer to zebu, camelids, and free-threshing wheats.
Did millet cause the Black Death?
The latest episode of the wonderful Ottoman History Podcast is about the Black Death. Or, rather, the Black Deaths. It’s an interview with Dr Monica H. Green, an historian of medicine specializing on the medieval period, who has brought together textual, archaeological and genetic evidence to question the dominant, Eurocentric — she calls it Boccaccian — narrative of the plague.
As she explains, prior outbreaks of plague in 13th-century Asia occurred at the edges of the ascendant Mongol Empire, roughly a century before the plague arrived in Western Europe. In our conversation, we learn how Green uncovered the new story of the “four Black Deaths” and in doing so, explore the historiography of the Black Death and how genetics, archaeology, and a fresh approach to textual sources have brought us to a deeper understand of one of history’s deadliest pandemics.
What’s this got to do with agrobiodiversity? Well, Dr Green summarized her findings in a tweet back in December (slightly modified for clarity):
- the Black Death started in the 13th, not the 14th Century
- it wasn’t just a Mediterranean or European phenomenon
- it originated with a spillover out of the marmot plagues reservoir in the Tian Shan mountains, leading to a Big Bang expansion in four directions
- it likely spread through the Mongol Empire via grain supplies
Whoa, grain supplies? Apparently.
In the foothills of the Tian Shan mountains, Mongol supply chains gathered up grain to feed their campaigning troops, particularly a kind of millet unique to the region. Sacks of grain were then transported to the fortresses and cities where the Mongols laid their greatest sieges between the 1210s and the 1250s, as far distant as Kaifeng in China and Baghdad in Persia. Something so insignificant as a few sacks of millet, into which a few plague-infected rodents crawled, might account for the worst scenes of human suffering the world has witnessed.
So much for that particular superfood. Whichever millet it is.