The desert: symbol
The desert is symbolic of how dramatically the world has changed. In the novel, deep and vast expanses of ocean had been replaced by warm and oppressive desert because of climate change caused by humanity. And without that climate change, the world would not have changed.
Water: symbol
Water is a powerful symbol of both the thing which drives human civilization and humanity. It is also symbolic of something which everyone around the world wants but struggles to obtain. Because of climate change caused by humanity, water has become a scarce commodity in a world which is dominated by desert (rather than primarily by water).
The ocean: symbol
The ocean is symbolic of safety. In the receding oceans, the remaining survivors of the climate disaster are able to find refuge and relative safety from the oppressive desert (no matter how fleeting it is as the ocean continues to recede).
The climate crisis: allegory
The drought is an allegory for the climate crisis, which is caused by humans and how poorly they treat the Earth. Within the allegory is a moral lesson: if humans want to continue to live free and prosperous lives, they need to treat the planet on which they live much better than they do.
Escape: motif
A very common motif in the novel is escape. In the novel, the characters (particularly the protagonist of the novel, Ransom) escape the places they are able find temporary refuge in. Most characters escape by chasing the receding ocean, which they hope will ensure their safety and security. In other circumstances, characters venture deeper into the desert.
