Regarding soil fertility, this is also rather complex, but obviously continuous cropping will tend to remove organic carbon, organically available phosphate and potassium, not to mention other trace elements, thereby leaving the soil less fertile unless very well managed.

Ice ages are not 'normal' in the geological history, and it will take tens to hundreds of millennia for a normal soil quasi-equilibrium to be reached. This 'equilibrium will also be lost both by human intervention and by accelerated climate change.