You ought to visit Iceland. Knowing that the entire island went from 30-40% woodland to being basically 100% deforested in a span of 100 years (the first 100 years following the Vikings arrival), and with the bare ground being fields of barren volcanic rock, to see all the sheep grazing pasture that exists today, gives you great appreciation for the amount of terraforming that was required to get even 1% of the land into that state.