Advertisements on the walls

We had nice stops all over the city a year ago. Very soon they were caught up with ads of various kinds of horns and pebbles across the surface, despite the presence of a huge board for ads (where two per two meters). I always break them down at every stop, but my efforts are a drop in the sea. How to fight more effectively?

You can, of course, sit in the bushes and shoot at killing... But I would like to do without a crime.