why not take it a step further and model climate, simple temperature model based on longitude/terrain type/planetary tilt/cloud cover. winds based on temperature variation, rain based on evaporation/temperature and then tie it back to terrain type being based on temp and rainfall. would allow for the local climate changes we've seen from deforestation and large dams. the model is way to simple to call it realistic, but it might add an interesting element to game play, is it really worth cutting down all the forests?? for the immediate production bonus?
Exactly. The Civ series has been screwing up forests again and again. In fact, in Civ 1 it was better to chop down all your forests as they gave you production which led to pollution.

I'd like to see a real benefit in leaving some of the forests. Crappy preserves didn't cut it. (No pun intended.
