Following on from my previous post, this is a brief introduction to my paper ‘The strong perennial vision: a critical review’1 in the journal Agroecology and Sustainable Food Systems and the response2 it evoked from the perennial grain breeders at the Land Institute.
The paper distinguishes between what I call the ‘weak’ and ‘strong’ perennial visions. The former involves combining the benefits of annual crops (fast growth, high allocation to seeds and other edible structures) with perennial crops (low input/low output, land conservation) and with other features of landscape design to optimise the goals of a productive and resilient/sustainable agriculture. The latter also considers perennial crops to be low input and land conserving but disputes the idea that they are necessarily low output – therefore it finds little or no place for annual plants in its vision of sustainable agriculture.
This strong perennial vision (SPV) is pervasive in the permaculture movement:see, for example, this post by Angelo Eliades, or this book by Mark Shepard, which I’ve discussed here and here. But its exponents with the greatest scholarly credibility are the perennial grain breeders at the Land Institute, who are attempting to overcome the environmental damage caused by the cultivation of annual cereals on the fragile steppe ecology of the US prairies by developing perennial grain crops which produce a high edible yield without the need for (much) tillage, fertilisation and pest control. Following the lead of their founder Wes Jackson3, Land Institute authors have argued that perennial crops can be just as productive of seeds as annuals4, and that developing such varieties will end 10,000 years of conflict between humanity and nature through annual agriculture5.
On the face of it, proponents of the SPV seem to have nature on their side – most wild floras are perennial, and wild plant ecosystems get by just fine without any tillage, fertiliser application etc. The puzzle then is why, if perennials involve less work for equal return with added environmental benefits, most human agricultures rely on annual crops, at least for their staple foods. Surely farmers through the ages weren’t so stupid as to engage in endless, environmentally-damaging labour for no added benefit?
Angelo Eliades thinks they were, arguing that the choice of annuals over perennials arose through ‘ignorance and lack of perspective’. I found that implausible, and it struck me that there’s likely to be some kind of ecological and/or biogeographical explanation for the annual preference in human agriculture. A more promising line of enquiry is opened up by Steve Gliessman in his book Agroecology6 in which he characterises perennials as essentially K-selected (slow and cautious reproducers – in mammalian terms, think whales), whereas annuals are r-selected (fast and prodigious reproducers – think rats). The plant ecologist Philip Grime7 builds on this r/K distinction in his ‘CSR’ theory, which identifies three plant strategies associated with habitat resource availability and disturbance: in resource-rich, disturbed habitats you get short-lived, fast-reproducing plants (‘ruderals’) which quickly produce a lot of seed in order to found the next cycle of growth. In resource-rich, undisturbed habitats you get somewhat longer-lived, often vegetatively reproducing plants (‘competitors’ – typically short-lived perennials). And in resource-poor, undisturbed habitats you get long-lived, slow-turnover plants more adapted to their own long-term survival than to short-term reproduction (‘stress-tolerators’ – typically longer-lived perennials).
To my mind, the CSR framework provided an immediate outline answer to the annual crop domestication puzzle. The key staple crops are ruderals or ruderal-competitors, and the key farming operations involve reproducing the conditions propitious for ruderal growth – disturbance (tillage), and resource augmentation (fertilising, weeding). Another side to it is the fact that the majority of crop assemblages in global agriculture accord pride of place to cereals. These are typified by large, starchy seeds which are essentially an adaptation to aridity and seasonal variation in precipitation. Only in the aseasonal humid tropics do we tend to find perennial staple crops, such as bananas. So the reasons our agrarian ancestors domesticated annuals and global agriculture continues to be so reliant on them are ecological and biogeographical, not because of human stupidity or because our ancestors made an ‘honest mistake’ (in Land Institute author Thomas Cox’s words8) by backing the wrong botanical horse.
That in a nutshell, or at least in a grass seed, is my argument as to why our agricultures as opposed to our wild floras are so dominated by annuals. Looking at agriculture through the lens of Grime’s CSR theory, it seems fairly obvious why it took the annual tillage/fertilisation course in seasonal climates that it did, and it surprises me that this explanation isn’t more widely noted. Some time ago I wrote to Professor Grime asking him if he thought my interpretation sensible, and in a brief response he answered affirmatively. This encouraged me to pursue my analysis which, following Grime, emphasises the importance of ecological constraint: there are various tradeoffs between reproductive allocation, longevity, growth, nutrient response, defence from herbivores and so on that are not easily soluble and which result in characteristic basic patterns in life-history, resource allocation and physiology9. I explore these in detail in my paper.
In the original version of the paper I took a wider look at perennials in global agriculture and submitted it to a different journal. It was rejected, partly on the recommendation of a reviewer who opined that nobody questions the role of annual crops in world agriculture, and also that plant breeders ‘yawn’ when people talk of difficult ecological tradeoffs in crop development, because overcoming tradeoffs is what plant breeders do all the time. So I decided to rewrite the paper with a narrower focus on those who manifestly do question the role of annual crops in world agriculture – ie. on the strong perennial vision, and on the work of the Land Institute in particular – to overcome the first objection. I also felt a certain irritation with the hubris of ‘yawning’ plant breeders, whose success in overcoming ecological constraint I consider far less impressive than is often supposed. The all-conquering power of the plant breeder to solve agricultural problems seems to be part of the present zeitgeist – whether through GMOs in mainstream agriculture, or through breeding perennial grain crops in ‘alternative’ agriculture. While I don’t dispute the vital role of plant breeding, I’m not convinced on either count.
That, in fact, is a key contention of the paper. Its meat (or starch, maybe?) is a series of subsections on historical crop domestication, sexual allocation, nutrient response, leaf economics, longevity and agroecosystem management which point up the many difficult tradeoffs that perennial grain breeding has to overcome if it’s to produce starchy perennial crops that come close to the present yields of annual cereals without the tillage, irrigation, fertilisation and pest control regimens which are so environmentally damaging in the latter case. I’m not saying that it’s entirely impossible for breeders to overcome these tradeoffs, but I do think it will be incredibly and unprecedentedly difficult. And it has not been conspicuously successful to date.
I also think that a hard distinction between annuals (bad) and perennials (good) is misleading. It seems likely that the agricultural solutions which will optimise productivity and environmental conservation will probably be competitor crops – perennials, yes, and relatively productive, but also relatively short-lived, and relatively demanding of nutrients. Will such crops produce tolerable yields and better environmental performance than our current suite of annuals? Probably. Will they produce as much as annuals but with fewer inputs, and will they end 10,000 years of conflict between agriculture and nature? Probably not.
If I turn out to be right, what are the implications for agriculture? I’ll look at this in more detail in an upcoming post, but I was struck by a comment from the perennial grain breeders at the Land Institute that “In sparsely distributed garden-sized patches, annual grains would have limited negative impact”4. As an advocate of small-scale, ‘garden-sized’ farming for many different reasons, that interested me, so in the latter part of my paper I developed this idea a little. To grow annual grains on a small scale as part of a diversified small farm economy would involve little new plant breeding work, but would involve huge sociological changes in human ecology – a point I briefly discuss in the paper. I also noticed that most of the perennial grain-breeding work to date has been done in semi-arid continental grassland biomes (eg. Kansas, where the Land Institute is based) which (1) arguably are at especially high risk of soil degradation through annual cultivation methods; (2) mostly developed annual grain agricultures relatively late historically as a result of colonial processes; and, (3) also happen to be the major grain exporting regions of the world. So I discussed this a little too.
So much for my paper. Let me now look very briefly the Land Institute’s response. They provide a threefold characterisation of my arguments as follows:
- Ecological theory suggests that perennial grains may yield less than annual grains
- Strong criticisms of annual agriculture are unfounded, both socially and ecologically
- Focus on perennial grains detracts from more important strategies for achieving agricultural sustainability
I’ll discuss these points in turn in my upcoming posts. In brief, the second one is basically a mischaracterisation of my argument, while the third issue is…complicated. Much the most important point of contention is the first. In essence, the Land Institute suggest that I interpret the tradeoffs implicit in the CSR framework too stringently and apply the model in too over-general a way to the issue of crop development. Whereas I argue that to produce high yielding perennial crops would involve trying to optimise in opposite ruderal-stress tolerator directions, they dispute the evidence for this, giving various examples of annual crop development that involves breeding in more S-type characteristics, and of perennial plants (including fruit and ‘early successional perennials’) with high reproductive allocation. They go on to say that CSR theory doesn’t address what happens if humans were to create a new type of habitat never before seen in nature, which is what they’re attempting to do in creating what they call a ‘domestic prairie’, that is, an untilled polyculture of edible perennial crops. Here, they suggest I misunderstand the phrase ‘domestic prairie’ as something requiring no human intervention other than harvest: their vision of domestic prairie on the contrary involves management for high resource availability. And they claim I err in thinking that because high-yielding perennial grain crops haven’t previously been found in nature, they’ll be difficult for future plant breeders to develop.
With the other two characterisations of my argument, the Land Institute take issue with me by citing evidence that “small-scale, diversified, labor intensive, locally adapted farming systems” such as those that served the civilisations of the Fertile Crescent, China, Rome and Mexico experienced “spectacular levels of soil degradation”. They also cite recent evidence from Michigan that plots growing perennial intermediate wheatgrass leach far less nitrates under synthetic or organic management than comparable plots of annual wheat. And quoting my comment that “the emphasis on perennial grains as a solution to the manifest problems of annual cereal cultivation paradoxically risks diverting attention from the importance of pursuing more diverse agroecological strategies” they state that I offer “no data on trends in funding, literature published or cited to support this concern. Nor [do I] substantiate the perception that groups working on what [I call] the strong and weak perennial visions are competing for attention or resources”.
That, I hope, provides a basic overview of the arguments and counter-arguments. In my upcoming posts, I’ll move on to some evaluations.
1. Smaje, C. 2015. ‘The strong perennial vision: a critical review’ Agriculture and Sustainable Food Systems, 39: 471-99.
2. Crews, T. and DeHaan, L. 2015. ‘The strong perennial vision: a response’ Agriculture and Sustainable Food Systems, 39: 500-515.
3. Jackson, W. 1980. New Roots For Agriculture, University of Nebraska Press; Jackson, W. 2011. Nature As Measure, Counterpoint.
4. DeHaan, L. et al. 2007. Perennial grains. In S. Scherr and J. McNeely (eds.). Farming With Nature: The Science And Practice Of Eco-Agriculture. Island Press.
5. Jackson, W. 2002. Natural systems agriculture: a truly radical alternative. Agriculture, Ecosystems and Environment. 88: 111-117; Cox, S. 2008. ‘Ending 10,000 years of conflict between agriculture and nature’ http://www.i-sis.org.uk/Ending10000YearsOfConflict.php.
6. Gliessman, S. 2006. Agroecology, CRC Press.
7. Grime, JP. 2001. Plant Strategies, Vegetation Processes and Ecosystem Properties. John Wiley and Sons.
8. Cox, S. 2008. Perennial crop systems – future of food. Focus On Perennials 6: 14.
9. Grime, op cit; Grime, J., and Pierce, S. 2012. The Evolutionary Strategies That Shape Ecosystems. Wiley-Blackwell.