There's a tv show on foxtel called crowd control, and they run experiments trying to change human behaviour.
They actually got people in New Orleans to race each other to pick up rubbish after they created a trivia game with 3 holes marked a, b and c, and you put a piece of rubbish in the hole to indicate your answer. If you get it right, you get a ticket. You needed 5 tickets to get a drink in the bars, so people were picking up rubbish off the streets to play and get drink tickets.
I know that won't suit our bush environment, but maybe we could modify the idea to suit? Points towards free camping in National Parks perhaps?