This is a perfect example of a positive externality. We tend to try to make the producers of negative externalities pay for the problems they create for the re

This is a perfect example of a positive externality. We tend to try to make the producers of negative externalities pay for the problems they create for the rest of us, but we rarely pay the producers of positive externalities for the benefits we all get from them. It's interesting that cities never put their money where their mouths are. If we really valued trees, we, the non-tree owners, would pay people based on the size and benefits of their trees.