I think the song is about nature being elemental and violent, and waiting for an act of violence to erupt. The Rider is the vessel for this violence. In the end he lays down his gun and resists nature, which I think think Cave thinks is elementally hostile (certainly The Proposition, which this song is from, suggests that). So in the end, the moon, the sun, the trees, etc. all howl "No" because he is resisting. It's a very beautiful song.
I think the song is about nature being elemental and violent, and waiting for an act of violence to erupt. The Rider is the vessel for this violence. In the end he lays down his gun and resists nature, which I think think Cave thinks is elementally hostile (certainly The Proposition, which this song is from, suggests that). So in the end, the moon, the sun, the trees, etc. all howl "No" because he is resisting. It's a very beautiful song.