Lyric discussion by mister care-too-much 

The song is about perseverance and love. The first stanza takes an environmentalist stance and says that the nature that provided for us will eventually reclaim us and the earth. The second and third stanzas are addressed to his son, Henry/"Hank", and his wife, Carson. He's telling them to stay strong and assures them that he'll stay strong for them too.

And wow, I didn't know that Colin's son is autistic. Makes this song so incredibly beautiful and sad.