One could plant that many pine saplings in a weekend with good hand tools. Mechanize it, spread the cost amongst many, I believe it wouldn’t cost, relative to what it offsetting, all that much. Land acquisition would probably be the larger obstacle.
I once worked for a short spell in a tree-planting squad in the highlands of Scotland. The seasoned planters were olympically fit and each planted around 100 saplings an hour across rough mountainside.
