I have been playing a bunch of games lately to test my mods and one of the big things that stands out is how sometimes the AI gets stuck because it runs out of places to build cities, in a way humans don't. Sometimes they just get stuck behind a barren land and it basically kills them via strangulation. This is because a smart player can use Birth of Summer or even just plan ahead and expand their ZoC to fertilize land. For obvious reasons these approaches are way to complicated for the AI to use correctly. Casting Birth of summer or building the correct buildings in the correct places is very complicated and requires planning ahead. So in order to really help the AI out I think there really needs to be a more AI friendly approach to fertilizing land. My idea is the below spell.
Growth Pulse: All cities controlled by the caster spread fertile land 3 tiles further then their ZoC, or if it's easier all cities gain +3 ZoC for 1 turn.
90% of the time this will result in one or several places to settle. Obviously in order to be useful at all the AI would have to know to cast this when it can't find a place to settle, but that's a relatively simple thing compared to trying to cast Birth of Summer. This would also be very lore friendly because restoring the land is supposed to a part of the lore and gameplay. mainly however it would just really help the AI.