This is a great chapter. Toensmeier really digs into some numbers, acknowledges where the numbers are real or estimates. He's very clear that carbon farming in and of itself is not enough and rather than make a guesstimate as to exactly how much, he says he's working on calculations with
Project Drawdown of which he is a senior fellow
Their mission statement:
Project Drawdown is facilitating a broad coalition of researchers, scientists, graduate students, PhDs, post-docs, policy makers, business leaders and activists to assemble and present the best available information on climate solutions in order to describe their beneficial financial, social and environmental impact over the next thirty years.
So serious people then!
If his numbers are to be believed, and I think they are, (his participation with project drawdown supports this very strongly) , then he's demonstrated that we know enough to have a serious tilt at this issue (climate change) from an agriculture perspective.
I specifically like how his argument doesn't boil down to 'We should all do permaculture' but takes a much more realistic view on expanding current models that work: no-till, cover cropping, pasture and grazing management, including silvopasture, and perennial cropping systems. His scenario sketch at the end of the chapter is wonderfully encouraging.
We're still very much in the background theory, and nowhere near the 'doing' parts of the book, but he's covered a lot of ground admirably quickly and clearly.
tl;dr Changing the way we do agriculture using current, proven practices will pull a chunk of CO2 out of the atmosphere