The Wall is a physical structure and the central symbol of the United Kingdom’s response to climate change in the novel. Building a Wall around an entire nation reflects the values of British society. A Wall both keeps people out and keeps people in. As a structure designed to keep people out, the Wall reflects the nation’s rejection of its responsibility to address climate change, despite the fact that the consumption habits and past industrialization efforts of higher-income nations are major drivers of climate change.

The Wall also changes people on the inside. There are real dangers outside the Wall, but also internal ones: The surveillance apparatus the United Kingdom builds and acceptance that outsiders are Others create a closed society in which people aren’t open to change. In addition, acceptance of the Wall creates a geographic space in which citizens and the government can exploit Others, remove children of Others, and transform Others into Breeders—practices that are inhumane and unethical. The Wall thus represents the failure of the country to live up to its ideals.

For Joseph Kavanagh specifically, the Wall symbolizes the lack of intimacy he experiences while he serves as a Defender. Joseph discovers this aspect of the Wall after the first attack of the Others, when he remarks that lack of connection is “a wall of its own.