Removing Features in city states.

[Yand_Durinul]

I would like to add the ability to remove features from within a city states territory, i.e. Trees (Vanilla) or Kelp Forest (Sukritact's Oceans Mod). Please can somebody help me with this as I have no idea where to even start.

Preferably with the Nau from the Portugal DLC.
I'm just dipping my toes in the water with unit functions/abilities and this is a fairly large step for me.