It’s easy to talk about "nature" as if it were one, simple thing. But nature is many things in this poem. For the female protagonist, it’s a potential paradise and a source of beauty. But nature also includes the forces of death and change, which can pull the rug from under you at the moment you feel happiest. In the final stanza, nature is a kind of "chaos" that surrounds us like the ocean surrounds an island, and it’s not clear how well we can know the meaning of anything in nature.
In the final stanza, the poet imagines that nature is completely foreign to human needs and desires, which, strangely, is why we find it to be so beautiful.