How we cite our quotes: (Chapter.Paragraph)
Quote #4
They sped above the mossy broke-back structures of a dead city. A whole waterlogged world of optimism, torn down by the patient work of changing nature. (16.53)
As Nailer, Nita, and Tool approach Orleans, they see the wreckage of nature; the city is "dead." And the optimism once felt has been "torn down." Nature takes on a much more sinister tone here, even though we know that nature isn't good or bad in the novel—it just is.
Quote #5
She waved at the drowned ruins, and a flash of ocean. "They used to drill out there, too, in the Gulf. Cut up the islands. It's why the city killers are so bad. There used to be barrier islands, but they cut them up for their gas drilling." (16.60)
Bacigalupi is imagining that human greed has caused the destruction that created the drowned cities. Although this is a sci-fi novel, there's enough truth in what Nita says that this serves as a warning against human greed.
Quote #6
The merchants and traders had had enough of the river mouth and the storms, and so left the drowned city to docks and deep-sea loading platforms and slums, while they migrated their wealth and homes and children to land that lay more comfortably above sea level. (17.10)
Natural events don't just wreak havoc on the terrain, they inflict harm on the people, too, and not everyone is equipped to deal with the volatility of the coast. So, like we see today, those with money move to safer places, and those without money must make a life for themselves where they can. And this means that, oddly, nature's actions increase socio-economic division.