This post offers some further notes on the issue of carbon farming and regenerative agriculture, arising out of the discussion in this recent post of mine, particularly via the comments of Don Stewart. Don set me some onerous homework – a lengthy presentation by Elizabeth and Paul Kaiser of Singing Frogs farm in California, another lengthy presentation by David Johnson of New Mexico State University, and an interview with Australian soil scientist Christine Jones. Diligent student that I am, not only have I now completed these tasks but I’ve also read various other scientific papers and online resources bearing on the issue and am duly turning in my assignment. I hope it’ll provide some interest and a few points for discussion.
I started out with considerable sympathy towards carbon farming and regenerative agriculture, but with a degree of scepticism about some of the loftier claims made on its behalf by regenerative agriculture proponents (henceforth RAPs). And in fact that’s pretty much where I’ve ended up too, but with a somewhat clearer sense of where my grounds for scepticism lie. I hope we’ll see a shift towards more regenerative agriculture in the future. But if that’s going to happen, the RAPs will have to persuade a lot of people more inclined to scepticism than me about the virtues of their proposals – and if they’re going to do that, I think they’ll need to tighten up their arguments considerably. Anyway, in what follows I define what I understand regen-ag to be and then critically examine some of the claims about it.
Defining regenerative agriculture and carbon farming
Doubtless there are numerous possible emphases, but the fundamental idea revolves around restoring or maintaining the biological life of the soil, in particular the fungal component. Working as symbionts to plants and other soil organisms, fungi are able to deliver nutrients to plants that are otherwise unavailable, and also to sequester carbon by absorbing carbon dioxide from the air and turning it into stable organic carbon compounds in the soil. In order to achieve this, it’s essential to avoid tillage, since this destroys the fungal hyphae in the soil, and to keep the soil covered with living plants at all times so that there’s a healthy rhizosphere (root zone) interacting with the soil food web. It can also be necessary to inoculate the soil with the right kinds of fungi – apparently, not just any fungi will do1.
So the three key characteristics of this kind of agriculture are zero tillage, continuous cover cropping and fungal inoculation. David Johnson states that a one-off ‘dusting’ of 400-500lbs of inoculant per acre (that’s 450-560kg per hectare for those of us still hanging on in there in Project Europe) is all that’s necessary to create the right initial conditions in the soil for many years to come.
Proponents of this kind of regenerative agriculture have variously claimed that it can:
- Protect soil from erosion and depletion, and indeed actively build soil
- Provide adequate crop nutrients with minimal external inputs
- Produce high yields
- Produce healthy crops that are weed and pest-free
- Sequester human greenhouse gas emissions – possibly all of them
- Earn greater financial returns for farmers
- Improve human health
If all that turns out to be true, then this is fantastic news. But these are powerful claims, and it’s surely reasonable for them to be examined closely before we collectively hitch our wagon to regen-ag. So here, in each case I try to highlight things that seem to be more or less well established beyond reasonable doubt, and things that don’t seem so well established, at least to me. I’m not an agronomist or a soil scientist, so doubtless there are things that aren’t obvious to me which are obvious to others, though I have a sneaking feeling that a few of the non-obvious things are brushed aside a little too quickly in the Regen-Ag movement, perhaps because they don’t quite fit the narrative. And then there are one or two things I’d like to highlight that seem not well established at all. So we have green-amber-red: Small Farm Future’s traffic light guide to Regen-Ag.
- Regen-Ag protects and builds soil
I think it’s reasonably well established that no till, continuous cover-cropping protects soil from physical erosion better than tillage farming2, so we can start with a green light. It’s not an all or nothing thing, however. There are places with strongly erosive conditions where it’s a really, really bad idea to practice tillage agriculture from a soil protection point of view, and others with less erosive conditions where perhaps it’s only a slightly bad idea. Sensitivity to local context, and other pressures, is in order before deciding how much to censure tillage practices. Nevertheless, I think it can be agreed that tillage is best avoided whenever possible. Of course, the mainstream ‘no till’ approach involves using copious quantities of glyphosate, synthetic fertiliser and heavy, compacting machinery of the kind that the late, lamented Gene Logsdon subjected to gentle ridicule in various articles3. It’s tempting to say that’s a whole different ball game from Regen-Ag, but actually it isn’t entirely. Many farmers lauded for their Regen-Ag credentials like Gabe Brown and Gail Fuller routinely use glyphosate or other herbicides, even if at a lesser rate than conventional farmers4. I’m not inclined to criticise them for it, but it falls some way short of the desiderata for a healthy soil food web generally emphasised by the RAPs, without apparently receiving much discussion.
In terms of actually building soil, RAPs like Christine Jones and Elaine Ingham commonly critique the widespread notion that soil formation is a slow process, arguing that topsoil formation can be ‘breathtakingly rapid’5. But it’s rarely stated how rapid. Many no till, regen systems I’ve seen involve importing compost in bulk. But that’s not soil building – it’s soil importing. So my question is, allowing for an initial ‘dusting’ of inoculate à la David Johnson, how quickly do soils under a regen-ag regimen typically ‘build’ with no subsequent imports or amendments, with crops being removed from them for human consumption all the while? Until that question is satisfactorily answered, I think the ‘building’ claim stays on amber.
The Kaiser’s Singing Frogs farm seems to involve importing quite a lot of compost, even if it’s used only as a soil amendment that helps stimulate the soil food web. In addition to the compost applied to their growing beds, they raise most of their plants initially as transplants in the greenhouse, which presumably also involves importing a lot of substrate. This is how most small market gardens operate, including mine (we import woodchip and some substrate). In our present economy, flush with fertility and fossil fuels, it’s a rational thing to do. But you do have to pay close attention to where the compost or substrate comes from, and how feasible it would be to scale its supply up across the farm sector as a whole, before concluding that soil-building of this sort has global replicability. Historically, in low energy situations the choice was essentially between tillage farming or diligent and extremely labour-intensive cycling of nutrients locally. As we confront the possibility of a lower energy future, it seems unlikely that farming systems based on importing compost in bulk will figure heavily.
- Regen-Ag provides adequate crop nutrients
There seem to be two ideas here. First, that once the soil food web is in good heart, there are enough nitrogen-fixing bacteria in the soil to give the crops all the nitrogen they need in better forms than synthetic fertiliser, which ultimately has a destructive effect on the soil food web and on the ability of plants to take up nutrients5. And second, that the overall metabolism of the soil food web makes the other nutrients needed by the crop more available than in soils compromised by conventional practices.
The first point seems plausible to me, but not definitively established. I think more quantitative evidence is required, which I didn’t find in my various readings of the RAPs. Much as I share the dislike of the RAPs for synthetic fertiliser (and I’ve never used it myself), about 40% of the current global food supply is based on the application of synthetic nitrogen compounds – this was a major limiting factor in 19th and early 20th century agriculture, and it seems doubtful that human populations would have reached their current level without the invention of the Haber-Bosch process6. Undoubtedly, there are downsides to synthetic fertiliser. The RAPs may be right that ultimately it’s destructive of soil health. And we may be able to do without it – either by careful cycling of organic nutrients, or by the kind of soil food web route advocated by the RAPs. Various people – including me – have asked whether it’s possible to feed the world through organic farming alone, and answered with a tentative yes. It certainly makes sense to start weaning ourselves off synthetic fertiliser whenever we can, but from a global food security viewpoint our current tentative yeses don’t seem quite enough for us to blithely ditch the synthetics quite yet. Generalised or anecdotal claims that crops will do better without synthetic fertiliser are all very well, but I think such claims have to stay on amber until more quantitative data is forthcoming.
In relation to other nutrients, I get that a thriving soil biota can pull in carbon, nitrogen and oxygen from the atmosphere, but all the other nutrients have to come from the soil. David Johnson talks about the “increase in the availability” of such nutrients in his version of Regen-Ag, which he calls “Biologically enhanced agricultural management” (BEAM)7. It’s plausible to me that a healthy soil biota makes these nutrients more available to crops than they’d otherwise be, but (unlike C, N and O) it can’t conjure them out of thin air. So if crops are being taken off, then it seems to me that ultimately these nutrients are being mined from the soil, unless they’re somehow getting put back too8. But since Dr Johnson also enthuses about retaining his modern lifestyle and jetting off to distant conferences, it doesn’t seem that he’s thinking of a smallholder-style world of careful nutrient cycling. So I wonder where these nutrients are coming from. Maybe the RAPs would argue that there are effectively limitless quantities of them in the soil if only they can be made more available by the soil biota – I’ve heard Elaine Ingham imply as much9. But again, I’d like to see more quantification of this point. By my calculations, for example, the 65 million of us in the UK need to consume about 24,000 tonnes of phosphorus annually, which would minimally involve stripping the phosphorus in its entirety out of about 24 million tonnes of soil every year, and that at an improbable 100% extraction rate. So for the moment I consider this another amber, at best.
- Regen-Ag produces high yields
Yet again, I’m struggling to find much quantification here. In Christine Jones’s article, various farmers practising regen-ag are mentioned who are “getting fantastic yields”10. Well, how fantastic? Wheat yields in the USA, for example, have averaged 46.7 bushels per acre nationally over the last five years11. How do the wheat yields of regen-ag farmers compare? I’m not seeing too many hard and fast figures in the literature.
Let me unpack this point a little under these four heads:
- Biomass and harvest index
- Necessary yield
- Competition and agronomic variation
- Cropland-grassland balance
Biomass and harvest index: David Johnson presents figures for the most productive natural ecosystems which suggest they produce up to four times more biomass than agroecosystems despite all the fertilisation and irrigation lavished on the latter. From this he infers that “We’re doing something wrong”12. But the main purpose of agroecosystems isn’t to maximise the production of biomass, it’s to produce digestible human food – carbohydrates, proteins etc. Human crop breeding efforts have actively tried to reduce the amount of inedible biomass relative to the edible portion of the crop (ie. increase the harvest index). In this sense, Johnson’s comparison presents little useful information. Further, the high productivity natural ecosystems he identifies are all from hot and/or humid places (swamps, rainforests…even kelp beds). It’s not clear that the same is true of his agroecosystem figure, so I’m not sure he’s comparing like with like. Then Johnson presents data showing that his BEAM system produces way more biomass than even the natural ecosystems. He doesn’t always make it clear exactly what these high biomass BEAM plants are, but they generally seem to be cover crops which, by definition, are plants that are unusually good at quickly producing copious leafy biomass in the short-term. So it’s not necessarily surprising that they outperform the range of plants found in natural ecosystems and agroecosystems. High biomass production can be one important agricultural goal, but what’s ultimately of greatest interest is the yield of the edible portion of the crop. The table that Johnson really needs to present here is the yield of edible biomass or of metabolisable human nutrients in the various different regimens. It’s impossible to know if we’re ‘doing something wrong’ in crop yield terms until he does.
Necessary yield. Of course, yield isn’t everything. A lot of crops are fed inefficiently to livestock, or exported, or end up as food waste. Undoubtedly there’s some slack in the system, so it doesn’t necessarily matter if regen-ag yields are lower than conventionally-grown crops if they bring other benefits. As with enthusiasts for perennial grain crops, the RAPs seem to feel the need to claim that crop yields are as good or better than conventional crops, when this may not be necessary for their case, and potentially draws us into needlessly oppositional arguments. But ultimately it’s necessary for any agricultural system to yield enough to feed the people relying on it. What counts as enough isn’t an exactly quantifiable number, but it should be roughly quantifiable, and I’d like to see the RAPs roughly quantify it.
Competition and agronomic variation: at one point in his presentation, David Johnson likens our major crop plants to weeds and says “we’re good at growing weeds”. That’s exactly right. The basic characteristic of most of our major crop plants is that, like most weeds, they’re pioneer, short-lived (usually annual or biennial, sometimes short-lived perennial) plants that usually fare best in disturbed (ie. ploughed), highly fertile ground. As argued above, disturbed ground isn’t ideal for other reasons, so if we’re going to grow our standard crops in regen-ag systems, then essentially we’re going to have to ‘trick’ them into growing in circumstances they don’t particularly favour. In particular, we’re probably going to have to grow them through cover crops that may compete with them for water, light and some nutrients, even if they may donate other nutrients (like nitrogen). Therefore we might expect them to yield less. Generally, the way farmers bicrop cash crops with cover crops if they don’t use herbicide (which in fact most of them do) is to use some kind of inherent seasonal check to the latter (eg. flooding, extreme heat/drought, or extreme cold) or else by damaging them mechanically by some method that falls short of full tillage. But that’s not possible everywhere – for example, in the moist temperate zone where I live, cover crops can happily grow more or less year round and I’m not sure there are obvious ways that, for example, a cereal crop could be established directly into them with uniform success and good yields. This article about Kansas regen-ag farmer Gail Fuller says “Instead of trying to figure out the best way to terminate a cover crop or pasture, Fuller is looking for ways to knock it back for a few days to allow the cash crop to compete as a companion crop”. Where I live, I don’t think ‘knocking back’ a cover crop for a few days would be anything like enough to establish a successful cereal crop into it – which is why cover-cropping farmers here continue to use glyphosate routinely. My feeling is that further experimentation with cover cropping may eventually mitigate this problem, probably at the cost of some yield loss. But it doesn’t seem to me that humanity has really cracked this one yet. I think the RAPs need to discuss this issue more clearly, perhaps with an acknowledgment that – as with their ideal cover crop – it’s not yet cut and dried.
Cropland-grassland balance: many of these cash crop-cover crop trade-offs disappear when the focus shifts to farming ruminants on grass, because – notwithstanding many farmers’ taste for temporary perennial ryegrass – the cash crop in this instance is essentially a long-term cover crop, which therefore fits easily into the logic of regen-ag. Perhaps it’s no coincidence that the farmers who get star billing as regen-ag pioneers are often ranchers on extensive, semi-arid grassland who are restoring soil and vegetation in the aftermath of ill-advised intensive grazing or tillage. All credit to them, but in terms of global food production it would be stretching a point even to call this a sideshow. The problem with grass as a crop is that humans have to jump a trophic level in order to be able to consume it as beef, lamb etc. and – as the likes of George Monbiot tirelessly, and correctly, remind us – this is pretty inefficient energetically. The contribution of rangeland beef to global food intake is minimal. On this note, Gabe Brown is frequently cited as a regen-ag pioneer. I haven’t yet established exactly what Brown’s system is and what his yields are, though it seems he has long fallows in his grazing rotations. Makes sense…but then he has a lot of (presumably cheap) acres to play with. Maybe his yields stand up even so. If so, it hardly fits into a Boserup model of agricultural intensification. Gail Fuller says “with low grain prices my bottom line is better grazing cover crops and pastures than growing corn…Right now, I make more money grazing”13. Of course, that’s absolutely fine at the individual farm level (though maybe it raises a question mark or two about those ‘fantastic’ regen-ag yields). But at the global food system level, it probably wouldn’t be fine, and we need to address that too.
In summary, I’m open to the idea that regen-ag methods produce ‘fantastic’ yields, but I’d like to know what they are. If no-till, cover-cropping methods can match or surpass tillage plus added-fertility methods for crop yield (rather than biomass yield) then that indeed would be fantastic – but it would run counter to what we’ve learned historically about agricultural development. Even if they can’t match them, it may not matter if they can yield enough. But some good, global quantification is necessary. For the moment, there are many ambers here.
- Regen Ag produces healthy crops that are weed and pest free
It seems plausible that a healthy soil biota, with fungal networks optimising nutrient transfer, will produce healthy crops – perhaps healthier than ones propped up by an agri-chem plus tillage approach. At the same time, as mentioned above, most of our crops are based on weedy, pioneer species that like to hoover up nutrients in disturbed soil, and they’ve been further bred to amplify these characteristics. So the idea that they’re happier in undisturbed fungal soils arguably requires demonstrating, rather than being assumed. I’d judge this assertion to be hovering on amber.
No doubt it’s true that healthy plants are more resistant to weeds and pests. This has long been the refrain of the organic movement, and I think it’s defensible so long as you don’t overplay the argument. Our crops, remember, are basically weeds, and the kind of soils they like to grow in will generally be to the liking of other weeds that humans don’t want. At Singing Frogs Farm, the Kaisers emphasise the use of mature transplants as a strategy to prevent weed ingress. That makes sense in the context of a small market garden, but it speaks of weed management, not a weed-free agronomy. It’s also labour and compost-intensive. It’s not necessarily applicable to broadscale farming – unless the argument is that we should minimise the latter and emphasise small-scale, labour-intensive farming. That, I think, is precisely what we should be doing. But we won’t have banished weeds, and we’ll have to scratch our heads to find the necessary inputs.
The pest issue mirrors the weed one. Different kinds of pests adapt to different kind of cropping regimens in different ways, and again it’s a matter of management rather than banishment. The Kaisers discuss the bird and insect problems they have and the crop covers they use to minimise these – so clearly they have pest problems. I find implausible the notion of a farm so tuned in to the natural world that none of its crop ends up in the stomachs of wild critters. Indeed, a farm tuned in to the natural world probably ought to be one in which some of its crop does end up in the stomachs of wild critters.
For me, it’s a red light on this claim.
- Regen ag sequesters human greenhouse gas emissions – possibly all of them.
It’s generally agreed that soils can act as a sink for carbon, and that soils containing a healthy food web are better at sequestering it – for example, through the fungal creation of chitin which holds it in a relatively immobile form. So I think we can probably award a green light to the basic claim that regenerative agriculture can sequester carbon. I say ‘probably’ because there are studies that contest the idea of carbon sequestration through no-till regimens14 – it seems to be the case that the ‘regimen’ can be more important than the ‘no till’. Still, I think it would be fair to say that the balance of the literature suggests sequestration is at least a possibility.
Even so, I’d like to make four caveats.
First, I’d hope we can all agree that the best form of carbon sequestration is the one where humanity leaves the world’s hydrocarbons in their well sequestered present locations deep down in the earth. Carbon sequestered shallowly in soils by living organisms is always going to be more potentially mobile. You could argue that, in practice, humanity just isn’t going to leave all that energetically useful carbon where it currently lies in the rock, and that we therefore need to think about other mitigation strategies. Fair enough. But David Johnson’s insouciance about continuing to live our present high energy, fossil-fuelled lifestyle while mitigating its effects through shallow sequestration in living soils doesn’t inspire me with a great deal of confidence.
Second, no till farming doesn’t have it all its own way in terms of greenhouse gas emissions, because it’s typically associated with greater nitrous oxide emissions – and in some situations these outweigh the carbon sequestration gains: “increased N2O losses may result in a negative greenhouse gas balance for many poorly-drained fine-textured agricultural soils under no-till located in regions with a humid climate”15. That sounds like an apt summary of many of the soils where I live. Proof again, if it were needed, that in agriculture as in many other things there are no one-size-fits-all solutions.
Third, there may be a limit on soil sequestration potential. Regen-ag heroes like Gabe Brown are lauded for taking on farms degraded by over-tillage and soil carbon loss and then building up the soil carbon stocks. But it seems to be the case that you can only build up the soil carbon for so long16 – we’re talking years, or decades at most – before it reaches an equilibrium where there’s no agricultural benefit to increasing carbon (as the Kaisers have already found) and it gets harder to do so anyway. So there may be a fairly short time-frame in which the carbon sequestration benefits of regen-ag are operative. Experiments like David Johnson’s have also been undertaken under short time-frames so far. Some caution about how much we can extrapolate these findings long into the future is probably in order.
Fourth and finally, we come to the vexed question of how much of the carbon that humanity is adding to the atmosphere can be sequestered in soil. The scientific consensus seems to be something in the region between 7-16% of current emissions17 – a useful amount, certainly, but not decisive enough to keep the climate change wolf from the door. RAPs like Christine Jones and David Johnson think that the potential is much greater, but frankly I’m doubtful of their claims. Jones appears to have something of a track record of questionable over-estimations of soil carbon sequestration potential of such proportions that it’s prompted even luminaries of the alternative farming movement such as Simon Fairlie and Rafter Sass Ferguson to distance themselves from her claims18.
Meanwhile, Johnson argues that since fossil fuel combustion is only responsible for about 3% of the carbon in the global carbon cycle, it’s better to focus mitigation efforts on the biotic side of the cycle. This strikes me as specious. True, there are large natural sources, sinks and fluxes of carbon which dwarf the anthropogenic ones, but these are well-established patterns that aren’t significantly responsible for the radiative forcing we’re now seeing as a result of adding new carbon to the cycle. And if I understand this right, this new carbon, this 3% (I think it’s possibly more than 3% if you consider all anthropogenic causes of radiative forcing), is being added every year. However we tend the soil, can we really expect the existing carbon cycle, its soils and vegetation, to take care of an additional 3% on top of its relatively stable totals on our behalf in each and every year for the foreseeable future so that we can continue flying around the world to go to soil carbon conferences? That’s a very large demand to place on Mother Nature. I suspect she has other plans. If the claim is that on the basis of a few short-term, small-scale, local experiments like Johnson’s we can be sure beyond reasonable doubt that all anthropogenic carbon emissions can be stably sequestered long-term in agricultural soils, then I fear I’m looking at amber turning to red.
This isn’t the first time it’s been claimed we can adopt agricultural practices that will sequester all anthropogenic carbon and banish our climate change woes. Those earlier claims were shown to be spurious19. The same outcome seems likely this time around.
- Regen-Ag earns greater rewards for farmers
I think the basis for this claim is that regen-ag farmers spend less on agri-chemical inputs, presumably without a concomitant decline in outputs. So it’s plausible that the current handful of regen-ag pioneers are making a bit more money just at the moment. But unfortunately markets don’t fix food commodity prices at levels determined by outmoded technical inputs – in fact, they barely fix food commodity prices at levels determined by inputs at all. If they did, I’d be a rich man. So if regen-ag proves itself and spreads, then absenting major structural change in the global political economy, no farmer is going to get wealthy from it, because commodity prices will adjust. In other words, it’ll play out the same way as every other technical innovation that’s enabled farmers to increase yields or reduce inputs without for the most part becoming notably better off. Even David Johnson concedes that farmers will need to be paid in order to adopt his BEAM approach. He says that we shouldn’t expect farmers to bear the brunt of society’s environmentally-damaging behaviours. I agree, though historically they generally have done. Of course, in the long run it’s not sound business sense for Homo sapiens Inc. to erode away all its agricultural soils, so at some level it must ultimately be true that it ‘pays’ to adopt regenerative practices. But in the short-run, while I’m sure some farmers have improved their incomes as a result of adopting regen-ag approaches, I’m not seeing a persuasive argument for how regen-ag will in itself improve farmer income. Another red light.
- Regen-Ag can improve human health
The main idea here – one debated under my earlier post – is that without a healthy soil biota to transport nutrients readily around, our crop plants are unable to access the range of nutrients (particularly the micro-nutrients) that they need for their full health, with negative consequences in turn for human health. I find this idea intuitively quite plausible, but intuition only takes one so far. Proponents of mainstream agriculture are fond of saying things like “nitrogen is nitrogen”, and to be honest I’ve not seen much evidence to refute them. Evidence of harm to human health from the proliferation of nitrates and other agro-chemicals in the environment is clear, so there are grounds for shifting away from it on that basis alone. But evidence of harm to human health from impaired soil food webs is more elusive. It seems to be the case that the nutrient density of our food is in decline, but it’s possible that this results from eating high-yielding modern crop varieties with poorer micro-nutrient uptake and from a poorer overall diet20, not because of the non-availability of micro-nutrients in the soil.
Christine Jones has this to say about the link between current agricultural practices and cancer:
“Not that long ago the cancer rate was around one in 100. Now we’re pretty close to one in two people being diagnosed with cancer. At the current rate of increase, it won’t be long before nearly every person will contract cancer during their lifetimes. Cancer is also the number one killer in dogs. Isn’t that telling us something about toxins in the food chain? We’re not only killing everything in the soil, we’re also killing ourselves — and our companion animals”21
Let’s unpack these statements a little. In the UK22 the current cancer ‘rate’ in the sense of new cases of malignant cancer occurring each year across the whole population is 1 in 182, but that translates into the expectation that indeed around one in two people will be diagnosed with cancer in the course of their lives23. If by a cancer ‘rate’ of 1 in 100 Jones means that ‘not that long ago’ only 1 in 100 people got cancer at any point in their lives (compared to the 1 in 2 today) I’d like to know how long ago that was. It would certainly be much longer ago than the 20th century, and the problem is that when you go back that far there are lots of other causes of morbidity – infectious disease and accidents, for example – that confound the attempt to make inferences about cancer aetiologies from rate changes. The fact that cancer incidence in pre-modern populations was low doesn’t necessarily mean that carcinogenicity in those times was concomitantly low (though that might be the case).
The difficulties of inferring changing carcinogenicity from historic incidence rates are compounded by changing age structures. The population now has a larger proportion of older people than before, and since the incidence of cancer is strongly associated with age, a good deal of the increase in cancer rates is purely an artefact of the ageing population. Meanwhile, cancer incidence is currently reducing in many ‘developed’ countries24 – though as a result of complex, multifactorial influences that push in different directions. So the straightforward answer to Jones’s question – isn’t the secular increase in cancer rates telling us something about toxins in the food chain? – is no, you just can’t infer that. That doesn’t mean she’s necessarily wrong. For all I know, it could be true that there’s a declining intake of micronutrients (or an increase in toxins – Jones seems a bit unclear on this point) with a positive effect on cancer incidence. Though if the finger of suspicion is pointing specifically at the decline of soil food webs, I’d observe that tillage agriculture has been the norm in many places for a long time, so the link between increased cancer incidence today and the destruction of soil food webs seems questionable. In any case, what’s clear is that the evidence Jones cites in support of her ‘toxins in the food chain’ view doesn’t in fact support it. There does seem to be evidence linking high dietary intakes of heavily processed food with raised cancer incidence25. Given current dietary patterns, adopting a diverse diet of fresh, unprocessed food may yield more health dividends than a switch to a regen-ag diet.
I’ve dwelt at some length on this rather abstruse cancer issue partly because I think it’s bad intellectual practice to justify an assertion in relation to evidence that doesn’t actually support it, and also because I think sloppiness of this order will easily torpedo the RAPs’ claims about the evidential base for regenerative agriculture more generally as they try to build wider support for regen-ag – and that would be a shame.
I think the health claims for regen-ag currently have to get red light status – though that may change in the future. I find it plausible that numerous aspects of our present food system may be associated with increased cancer incidence. It’s just that I haven’t (yet) seen any plausible evidence linking regen-ag practices to reduced cancer incidence.
I won’t try to summarise what I’ve said above. All in all, my traffic light assessment of the RAPs’ claims suggests to me a few greens, rather more reds, and a lot of ambers. There are numerous reasons why moving towards a regen-ag approach and sequestering some carbon in soils probably makes sense, but there’s a distinct lack of convincing empirical evidence to support many of the stronger claims made by the RAPs. For now, I feel like I’m waiting on amber.
Note: My thanks to Don Stewart for prompting this line of enquiry and to Clem Weidenbenner for an informative discussion.
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- David Johnson
- Eg. http://www.pnas.org/content/104/33/13268.short
- Eg. https://thecontraryfarmer.wordpress.com/2010/06/16/no-till-is-a-big-white-lie/
- Eg. http://www.cornandsoybeandigest.com/conservation/take-soil-and-farm-beyond-conservation; for a discussion of this among British farmers, see https://anewnatureblog.wordpress.com/2017/10/30/thoughts-on-the-glyphosate-saga/
- V. Smil. 2017. Energy and Civilization, MIT Press, p.308; V. Smil. 2001. Enriching the Earth. MIT Press.
- David Johnson
- Disclosure: I once vehemently and obtusely sought to deny this point in an online discussion with an Australian scientist whose name now escapes me. Sorry, sir – I was wrong.
- E. Ingham. 2015. Presentation at Canadian Organic Growers’ Conference, Toronto, Feb 2015.
- David Johnson
- Gail FullerJ. Baker et al. 2007. Tillage and soil carbon sequestration – what do we really know? Agriculture, Ecosystems & Environment. 118: 1-5; Z. Luo et al. 2010. Can no tillage stimulate carbon sequestration in agricultural soils? Agriculture, Ecosystems & Environment. 139: 224-231.
- P. Rochette. 2008. No-till only increases N2O emissions in poorly-aerated soils. Soil & Tillage Research. 101, 1-2: 97-100.
- S. Singh. 2009. Climate Change and Crops; DEFRA (2007). The effects of reduced tillage practices and organic material additions on the carbon content of arable soils.
- IPCC; CGIAR; Singh, Ibid.
- S. Fairlie. 2010. Meat. Permanent Publications; Rafter Sass Ferguson.
- George Monbiot; D. Briske et al.
- M. Fan et al. 2008. Evidence of decreasing mineral density in wheat grain over the last 160 years. Journal of Trace Elements in Medicine and Biology. 22, 4: 315-24; F. Denison. 2010. Darwinian Agriculture. Princeton UP.
- https://www.ncat.org/wp-content/uploads/2015/08/Acres-story-for-web-posting-March15_Jones.pdfI’m not sure which country’s rates Jones is referring to. I’m most familiar with UK data, so I’ve used that – I doubt the conclusions I draw here would be radically different if data were used from other ‘developed’ countries.
- A. Jemal et al