One thing I find interesting is how much more traction the problem of litter in the ocean has gained, compared to litter everywhere else, or any number of the other problems we have. I wonder why this is. Perhaps people can still see the ocean as a wilderness, where litter doesn't belong, whereas we are very used to seeing highways etc lined with rubbish?
Ocean trash has interests groups supporting it. Plenty of groups taking money to deal with it (or not) and part of that is to advertise the issue to ensure more money keeps coming into this industry. There is are no large international organizations or government efforts going out there to remove all the trash outside the more commercial or industrial parts of town, no ones buying ads about it, so its not in the public awareness as much. It also doesn't help that over time people grow blind to it. Heres an experiment you can run: find some litter on the sidewalk and see how many minutes or months go by before someone bends over and picks it up who isn't paid to do so. Chances are it will be in the months to never category, unless the person picking it up owns the land under that trash.