Clark, I have just watched that vid.
The bit that has been attracting me for a long time is “Passive reforestation”
Greenland – Qinngua Valley
The Vikings we are told were winding down their farming in Greenland at the time of The Black Death,
last farms petered out in Tudor times.
So, before The Black Death, European farming, in Greenland was viable, no doubt helped by slavery.
But the point is, it must have rained enough and been warm enough for them to pursue that option, European type farming.
The largest Landmass and biome is the Northern coniferous forests/Taiga.
As the climate gets wetter and warmer, the tree line will go North – on its own, we need do nothing.