I find it difficult to disagree with anything this man says.
One thing I wish he had discussed, though, is the biological devastation that has been wrought by mismanagement of drylands. Drylands are a huge portion of the earth’s surface. “Drylands” are not necessarily deserts, but can be made into deserts by mismanagement, usually over time. Drylands are lands which might get plenty of moisture, but in concentrated intervals, with dry periods between.
It is entirely possible to greatly increase the biomass in drylands. My own region is “dryland” of a sort, though we get nearly four feet of rain per year. It is, however, concentrated in the spring and the fall, with long dry spells in between (except when there are El Nino conditions). The trick in preserving and increasing biomass is proper management of grasses, largely through the use of cattle. Interestingly, you can desertify land more quickly through the absence of cattle than you can with overgrazing, though overgrazing has been devastating in many places, most dramatically in south Africa and north China.
But you can also reverse desertification over time with use of the proper balance of forests and grasses and the proper employment of cattle in the latter, but not the former. It’s true, though, that you can improve the quality of tree stands with extraordinarily careful use of cattle.
I speak of cattle, though other animals can do the same job. It’s just that other animals that can have the same beneficial effects are nowhere near as useful to humans in other ways.
Of possibly passing interest, much of the huge “drylands” areas of the U.S. once held a staggering amount of biomass; much more than the 10% Dyson seems to be suggesting. Deep rooted grasses can impart a lot more than that. But that’s another story.