Basically it's about conserving the Earth. You take only what you need "necessities", thus leaving enough for everyone. You have to control your greed. The "family of trees wanting to be haunted" part is a little less straightforward - but basically it means the same thing. When you think of things that are haunted - creepy mansions, old shacks, the thing they all have in common is that they're really old and have a lot of history (old and worn-down = creepy). Thus, a tree wants to live long enough that it has the chance to become haunted.

Thanks a lot.

A correction of your question: "What does the chorus of this song mean?" Use "What does ____ mean?" when asking this kind of question.