What is the theme in Vancouver Lights by Earle Birney?

Nature is a theme. Birney's description of the relationship between nature and culture in "Vancouver Lights" is a metaphor for humanity's relationship to the universe and to history. In the first stanza the speaker, his vision "guided" by the moonless night, sees lights from the city "overleaping the sea jet" and "vaulting] the shears of the inlet," metaphorically suggesting that human beings have overrun nature, that human-made things such as cities dramatically affect the ways in which we see and interact with the natural world.