Good day, Imp
Not sure if this is what you are looking for in an answer. Savannah is largely longer grasses in the clear areas and this can be mudded to some degree time of year dependant. Arid is largely dirt with some rough in the clear areas with mud depending in time of year.
Now I'm not positive, but it seems if you generate a maps for example SUDAN and EAST AFRICA then use the editor to change them to arid or savannah your will get a different "take" for each type of terrain for each Area.
I have done this in the past and got these results.
Examples: Your East African Map changed to arid is more likely to still have more "wet" features. (more like North Kenya than the orginal South Kenya) Your Sudan map changed to Savannah will be a drier map. (A South Sudan Map)
Hopefully this was what you were curious about.
Bob out
