My experience and observation say otherwise. I have no incentive not to litter when I know no one will fine me. Still I get up and walk trash to garbage cans. Even with all the litter around, most people still walk trash to garbage cans instead of littering.
Most people don't shoplift even when they know they wouldn't get caught. Most people stop at red lights in the middle of the night when no one is around. Etc. Etc.
I've found living by my values the greatest incentive. The alternative is to try to accept that my comfort and convenience come at the cost of others' health and resources, which ate me up inside.
I think most people value clean air and water enough that when the culture shifts, they won't need material incentive.
Laws will follow behavior, not the other way around.