There's a lot of nature in "Meeting at Night" (the land, the sea, the moon, the beach, fields). In some instances, nature is clearly an obstacle, something that must be negotiated during the speaker's journey to the farm house. In other instances, nature is sort of like a blank sheet of paper, something on which the speaker can inscribe his own thoughts and feelings. For this reason, the various natural features in the poem also take on a symbolic role, representing things like passion and love.
The poem's interest in symbolizing nature suggests that nature isn't really "real," but rather that it is merely what we choose to think it is.
While the poem seems interested in nature, it's really more interested in the psychological processes by which we interpret and reflect on nature.