Why might bradbury have included teasdale’s poem in his story?

Bradbury takes his poem about the end of humanity on earth from the poet Sara Teasdale.  Teasdale's poem considers the relatively small impact humans have had on Earth despite their brutuality towards one another.  Penned in 1920, the poet was writing in the wake of the atrocities of World War I, the "War to End All Wars."  That war saw horrors like mustard gas, a first in the race of mankind to exterminate itself.  Little did Teasdale know how much worse things could get.