In my experience, libby tree-huggers are the problem.
I remember the Earth Day celebration on the Washington Mall...it took two days to pick up all of the trash they left behind.
Yeah, read this and tell me this ain't based on liberal eco-nut viewpoints instead of an effort to find a practical way to deal with any actual underlying problem from trailside litter:
“A lot of careful thought went into this plan and its implementation,” said Director Jarvis. “I applaud Grand Canyon National Park for its efforts to reduce waste and the environmental impacts created by individually packaged water. This is another example of The National Park Service’s commitment to being an exemplar of the ways we can all reduce our imprint on the land as we embrace sustainable practices that will protect the parks for generations to come.”