Yes, littering and picking up litter could be a self sustaining cycle but it is all a waste, better to not litter and not have to have it picked up. It is like digging holes just to fill them in again, rinse and repeat. The labor could be put to better uses.
Sustainability is not about preventing things from coming and going it is about keeping something going that we want to sustain without is having it go away because we used it all up.
Fishing is a great example. Some kinds of fishing had to be massively reduced because the fish population was so reduced that it was not able to reproduce its population and if nothing was done that fishery would have died out. Because sustainable limits on fishing were introduced the population recovered and those fisheries are expected to be able continue for long into the future.
I have lived in Maine, Florida, California and Louisiana. In rural areas of Maine, Florida, and Louisiana I have seen many shot up road signs, very many shot up road signs. Not so much in California. Same deal with litter and trash dumping.
Peoples attitudes about these things make a difference.
Yes, there will always be poor people and people who will litter but social pressures to reduce poverty and environment degradation will result in reduced poverty and a better environment. It will make the world a better place. I think that is not something that you care about and is part of the reason there will always be poverty and trash. Some people are part of the problem and some people are part of the solution.
TEK