I used to do that on all my canoeing trips, take an extra bag and clean up the riverbank as we went. I still do it when I go hillwalking. My current pet hate is the mountain of foosty bread that is liberally scattered all over the local park. People don't seem to understand they are not feeding the birds, they are feeding the rats, and if bread is blue it's not good for anything to eat! I'm not taking about a scattering of breadcrumbs, this is whole loaves, chains of rolls...