biomes that may change depending on their use

A change that I believe would be interesting for the game is the introduction of a desertification process: as trees are removed from a given biome—up to a certain threshold—the land would begin to turn into a desert. The reverse could also be possible: the revitalization of a desert area into a savanna or even a forest—potentially accompanied by the appearance or disappearance of local fauna, depending on the specific case. Naturally, this would not need to affect the lower levels.