At least some cultures are amenable to training not to litter everywhere. In the US there was a big campaign in the 1970's and 80's to reduce litter on roadside

At least some cultures are amenable to training not to litter everywhere. In the US there was a big campaign in the 1970's and 80's to reduce litter on roadsides and other places. $1000 fines and a general positive attitude to group action has reduced litter in most places in the US that a yearly or less pickup schedule can keep even urban highways pretty clean. Monthly street sweeping elsewhere does the job. I don't see (much) plastic litter in the landscape in the US. In other countries, maybe other methods are needed.