I didn't address all the possible nuances, but for the purposes of being precise: "reforestation at the scale necessary to act as an effective carbon sink is uneconomical".

As you must know, trees accelerate their carbon sequestration as they get larger. Also, fruit and nut agricultural species are frequently not robust enough, fast growing enough, or zone hardy enough to be good candidates for this either.

Yes, trees have economical value. Trees an a AGW-countering scale carbon sink are not. I'm in favor of a carbon tax/credit system in part for this reason.

Isn't that tearing them down, not putting them up?

Lots of it, yeah, but tree farms are a thing too. That's a matter of cost in modern times though. Currently faster/cheaper to convince a government to let you chop down rainforests, but that won't always be true.

Definitely curious how hard it would be to have drones plant trees in arid regions. Feels like I've seen some related projects before

Isn't that ok, though?

If I build a building out of wood, or print a book in a library, that carbon is sequestered at least as long as the building or book exists.

That's true, but you've netted zero on carbon. You need to put up more trees if you want to remove carbon. I mean, by all means tear em down, but you gotta keep putting them up.

I think that's the point.. Grow more trees and use the wood and the tables and books that are created are carbon that used to be in the air.