Review time. I'm sorry it's taken me so long to write this. Other things in my life have got in the way.
I started out very excited by this book. The more I read, and the more I dug into the references, the more concerned I became. This book does have some very strong points, already extolled by Burra. I don't see any point in revisiting those: there are plenty of things in this book to get excited about.
I don't think anyone should be getting overexcited.
First, carbon farming is clearly not a solution. In fact, Toensmeier is clearly aware of this, but the realities of marketing seem to have led to a grossly misleading title. A better title might have been The Carbon Farming Wedge.
How big a wedge? As so often, it depends. Pre-industrial levels of atmospheric CO2 were in the region of 280 parts per million (ppm). It's generally accepted within the scientific community that the upper safe boundary is in the region of 350ppm. The recent winter's peak level topped out around 407ppm, and it's rising at around 3ppm annually. A rapid decarbonisation scenario would take us to around 450ppm. The Intended Nationally Determined Contributions leading up to the Paris conference would take us to a cataclysmic 675ppm. A best-case carbon-farming sequestration path would remove 50ppm of that. At present, the technology to remove the rest from the atmosphere is science fiction: it's also a massive engineering problem that would require us to remove more carbon than we produce in food, or mine in iron ore.
I liked the wide strand running through this book that addressing the threat of climate change is linked to a long list of global justice issues. The author is clearly aware of the requirement for those of us in the Global North to make do with less, while addressing the needs of poor farmers in the Global South, especially women. I'm not sure that the author perhaps brings the broader issues into sufficient focus, but he provides the resources for those who want to learn more.
I think there are two key flaws in this book. I spent a certain amount of time chasing references to points that interested me, such as what little we know about the temperate homegarden, or what we know as the forest garden. It quickly becomes clear that there is a dearth of reliable information about both yields and carbon sequestration potential. I think that those of us who have been working with such habitats have been grossly negligent in not addressing these questions.
In other cases the author fails to reference to primary source material, relying on summary reports (in one case I had to go through a summary report to a literature review to the primary sources) that often poorly supported some of his viewpoints. This is probably the greatest weakness with Chapter 7 on Livestock Systems. Some of these systems “work” by certain standards of “work”, but are in direct competition with more carbon-efficient systems for land and for other resources such as compost and mulch. The one system that does sequester substantial quantities of carbon involved – and may require – the planting of a known invasive tree species in order to fix nitrogen and overcome important limiting factors. In other cases carbon seems to be sequestered in spite of, not because of the presence of livestock.
Then there is the problem of yields. There are perennial crops that yield as well as existing annual ones, but they are few and far between and tend to be limited to the tropics. If we were to convert even much of our existing agricultural land over to perennials, we would need more land. This is at a time when much of our agricultural land is being lost to overtilling and overgrazing, as well as the related problem of desertification. Meanwhile we are entering a period of mass extinction not seen in 65 million years, not least due to the clearing of forests for agriculture, most of it to feed livestock. It is possible in polycultures to achieve an overyield, but the conditions in which that's possible, especially in temperate zones, are unclear.
The author makes his interest in maintaining present diets clear, but a closer reading indicates he's interested in maintaining the diets of the rich Global North, much less so the poorer Global South. He makes much of indications that some forms of grazing can sequester carbon, but a closer reading of his reference material shows that this is very small (perhaps 4% of annual emissions on over a third of our agricultural land) and seems to be mostly in spite of, not because of, the livestock. He makes the point that cattle, in particular, can have up to half their diets met using crop residues, but for these they are in direct competition for mulch, mushroom substrate and even biofuels. At the same time, other practices beat grazing hands down both in terms of carbon sequestered and, in most cases, protein produced. Most also depend on imported supplementary feed grain. What he seems to mean is that the richer portion of the Global North can continue to eat beef, while everyone else needs to eat beans. While I'm more than happy to eat beans, I have issues with the double standard. He is clear that we need to stop feeding grains to livestock, which would free up a lot of agricultural land – which then allows the more affluent to continue to eat meat from pastures, which have their own environmental problems and sequester minimal carbon.
There is another issue with ecosystem integrity where I think that Toesnmeier falls. In some cases, the introduction of novel species has done considerable damage to existing ecosystems. Plants have rarely, if ever, been the direct, sole cause of the extinction of another species, but there have been many where they have been a contributory factor. Toensmeier actually complains that he has been restricted by important biosecurity protocols when attempting to establish homegardens. I have little sympathy: around ten per cent of the plants listed in this book make a listing on an invasive species database. While this does not mean they would, or even might, become invasive in your region, it seems important that intelligent evaluation of each individual species takes place before it's introduced.
One of my other concerns is that perennial carbon farming could be leading us into a trap. On a low-emissions pathway it may help us squeeze through a narrow window in which we can feed if not everyone then at least a substantial proportion of the human species. On a high-emissions pathway the disruption in the climate could see massive dieback of critical food crops with nothing to replace them. In such circumstances we'd also lose the carbon in the soil back into the atmosphere.
There is another problem in that in many parts of the world the transition process may need to be led, for reasons of global justice, by indigenous peoples, few of whom have been major causes of the problem and many of whom are unlikely to be well educated about it. My reading elsewhere has shown how pastoralism is leading to issues of overgrazing and competition for land with other practices. This is often in cases where those with cattle are those who are relatively economically privileged, at least within their own communities, presenting competition with poorer members of those communities, especially women. At the same time, imposing a solution from outside presents a whole range of other issues. While Toensmeier is clearly aware of the needs of the Global South there are as many complexities there as there are here in the Global North.
He's also aware of the economic issues involved in the transition. His analysis of potential solutions to this is weak. As always there is a conflict between systems that would work and systems that are politically viable in a world with extremely wealthy vested interests. There is a clear need here for the involvement of civil society in overturning the status quo. I've given a lot of thought to questions of “fair share”, and perhaps more of a focus could be given to what this means in practice for permaculturalists.
I think the greatest problem with this book is that it doesn't go far enough. This may be because the author does not want to scare away many of his potential readers. There is a thread running through this book that many things have to change, and I'd agree with him. He twice cites Naomi Klein and, in particular, her book This Changes Everything: she is on record as having the view that we are out of non-radical options, and I agree with her, but Toensmeier makes little of this. I think this thread needs to be more of a streak: a very wide streak. There are much broader issues about the way we relate to each other (and Toensmeier quite rightly talks about climate justice) and to the rest of the planet, and the tendency towards the objectification of the other (other humans, nonhuman animals, ecosystems and the planet itself, to name the more prominent ones) that are skimmed over, perhaps for any of several good reasons (not least lack of direct relevance to agronomy) This means the book is not the game changer it could be.
I do think it's part of that game changer. It's part of a broader picture (and I also recommend you read Klein's This Changes Everything, as well as many other books mentioned in this one).
This is a good book, and it's worth getting hold of and making good use of. I don't think it's the great book that others have made of it.