"We use the History Database of the Global Environment (HYDE) land use data from the year 1800 to pinpoint the native forest biomes that can be established on grasslands and pasturelands with the examined lifestyle change [Klei 2010]. We assume that only forests that have been converted since 1800 to grasslands or pasturelands can be reverted to their original biomes. As such, only about 41% of current grasslands and pasturelands are considered to revert to forests. These grasslands and pasturelands currently sequester 27 GtC on 19.6 MKm2 of land area whereas upon maturity, the native forests sequester 292 GtC. Therefore, the lifestyle carbon dividend of a global transition to a vegan lifestyle is estimated to be 265 GtC, which is more than the 240 GtC that humans have added to the atmosphere since 1750!"

https://www.climatehealers.org/s/GC13E-1206_handout.pdf

Wouldn’t it make more sense to grow hemp, which sequesters three to four times more carbon than trees, faster? Bale it & dump it into a subduction zone.

Better usage for the hemp would be paper & hemp crete (cheap houses) & textiles (first jeans were from hemp). Thousands of other possibilities, just search the net.

But as a solution for carbon storage? Not sure about that ... trees are perennial, after the forest is established there are no other costs associated, it's also a habitat for the wildlife, so the biodiversity/extinction problem would be solved too.

If we could mostly have synthetic food, then that would free a lot of very energy inefficient farmland.

Yes ... or ... hear me out ... if we could switch to plant-based foods, that too would free a lot of farmland. About 75% of it.