Nowhere was mentioned that Sulani isn't affected by the eco-footprint effects. Please show me a post saying so. It was mentioned that StrangerVille and destination worlds aren't affected (and also hidden lots aren't affected as sims can't live in them, but Realm of Magic says otherwise).
Sulani can be affected (I have made it a greener place). Just Sulani clean-up and eco-footprint are two different things. One does not affect another, so making the world greener won't clean up the island.
Also sunrays/northen lights and smog can be seen in Sulani.