I don't think I can fulfill this request. Canon states that the world has been around before the Avatar, and when Roku tells Aang he can die permanently, there's nothing to indicate it will have an adverse effect on nature other than the inherent problems of him not stopping the Fire Nation conquest. Now of course, given Ozai's tactics, that would destroy the world pretty handily, but the Fire Nation and Firebenders would go with it pretty swiftly, because purning that much land would put so much ash into the air that it would block out the sun, and therefor their primary source of power when the comet's not around, and also the only way they would be able to grow crops.

You're free to request something else though, four other things, actually.