I like that in these early parts of the book he summarizes the problem (climate change), and how agriculture fits into a climate change solution. It is a bit disheartening to read so many
unknowns in this chapter, and to read that many figures are just estimates without much research behind them. But, as he states it, systems have been developed that do sequester carbon - more research is needed to more accurately quantify how much carbon is sequestered, but there are systems that can, and in many cases, already do work in the world.
It seems that there are dangers to some solutions that have not been explored, such as
nitrogen fixing trees releasing highly hazardous nitrous oxide (?).
From an initial quick idea, his statement that "The more diversity, higher density, and longer life span of
trees, the more carbon is sequestered" points to incentivizing farmers and landowners to devote large areas of
land towards growing highly complex forests, designing in as many stories of vegetation as possible, and then leaving it untouched. Then incentivizing the same people to adopt dense commercial agroforestry operations.
He also makes a great statement about not cutting down existing forests to adopt carbon farming strategies - they are already in place and doing a great job of keeping soil in the ground!
I wonder how much potential there is for arid regions, as he just stated that by total land area alone there is massive potential, but not a lot of potential per unit area.