On our many rafting trips, one of my kids' responsibilities (back when
they were little tikes) was to scout the campsite every morning before
we put back into the river. They were pretty proud when they found
something. This scouting involved looking for microtrash too, so the
kids might pick up a little piece of bread or orange peel, etc. you
get the picture. This keeps the ants away from frequently used, though
remote campsites on the rivers. You would be surprised
Most rivers are 'permitted' rivers, as we call them, because a permit
is required to raft them and to use the approved campsites along the
shore. The rangers know which party camped where and, if not, they can
ask other rafting parties and inevitably find out who trashed what, or
one party might report another. The end result is that you will not
likely draw another permit for that river.
I will say this......most rafters are very good about cleaning up
after themselves as they expect to return many times. What I see when
camping in my Syncro can be pretty bad in comparison. It's ironic that
it is so much harder to clean up after yourself on the river, yet
these seem so much cleaner, during high use periods.

Gracias,
 Miguel