What are the themes in the short story "If I Forget Thee, O Earth...?"

This story was first published in 1951. Only six years ago, the world had witnessed the most devastating attack of two atom bombs on two cities of Japan. Following the deadliest Second World War, began an unprecedented competition among the U.S., the U.S.S.R. and their allies to supersede one another in developing nuclear weapons.

This escalation of nuclear arms race made the Third World War seem imminent. If it happens, the destruction would be unimaginable. Some...

This story was first published in 1951. Only six years ago, the world had witnessed the most devastating attack of two atom bombs on two cities of Japan. Following the deadliest Second World War, began an unprecedented competition among the U.S., the U.S.S.R. and their allies to supersede one another in developing nuclear weapons.

This escalation of nuclear arms race made the Third World War seem imminent. If it happens, the destruction would be unimaginable. Some believed it could lead to the annihilation of the mankind. The possibility of the destruction of the whole of our earth captured the imagination of people across the globe.

The main theme of the story echoes this fear of complete annihilation of the human race and the destruction of our beautiful planet.

The author Arthur Charles Clarke imagines a scary picture of our planet in the aftermath of a nuclear war. The earth is devoid any living being and

“… the portion of the disk that should have been in darkness was gleaming faintly with an evil phosphorescence”

This image evokes a scariest image of the earth if there's a  nuclear war. Nobody in the planet would wish to see the earth turn into an inhabitable planet. 

Thus, the story can also be read as a strong warning to stop the futile nuclear arms race. It can also be read as a sincere urge to bring an end to an atmosphere of mutual hostility between powerful nations and replace it with mutual trust and co-operation.

Moreover, the story compels us to stop and appreciate for a while the gifts that the nature and this planet have bestowed upon us:

“the hues of sunset skies, the moaning of the sea on pebbled shores, the patter of falling rain, the unhurried benison of snow,” and “a thousand others.”

We would certainly not like to be in the position of Marvin who had never known and would never know “the wonders” of the shining crescent” that were once the “rightful heritage” of mankind.