Given that The City of Ember is a planned post apocalyptic community under the earth's surface, it makes sense that we only get a few glimpses of the natural world. There are, of course, bugs and dust (we can't really imagine any scenario on earth without bugs or dust). And the citizens grow their own food under lamps. But there aren't animals, trees, mountains, or oceans. None of that. It seems safe to say that the citizens of Ember are pretty out of touch with the natural world—that is, until Lina and Doon figure out how to escape to the mysterious world above.
The people of Ember live poor, sad lives without nature. They won't be happy until they move back up to the earth's surface.
You can take people out of nature, but you can't take the nature out of people.