I doubt that it is an adult that leaves the garbage behind. It's a younger ignorant crowd just looking for a place to party.
The faith you have in "adults" and your contrasting complete dearth of faith in young people concerns me.
Also after going past the dam I scould smell marijuana. It has become a party spot for young people.
I usually bring some nature-enhancing grass along (so long as it isn't offensive to whomever I happen to be with at the time) and if anything, I feel more inclined to preserve all of the beauty around me after indulging.
I'm tired of people feeling the need to target a specific group over issues like this. I'm young, and much of the time I have to keep my young friends "in check" when we're in the wilderness to ensure that they leave everything as they found it. When I visit places like Fossil Creek and Oak Creek, however, I find that age is not consistent amongst people who aren't concerned about preserving nature; it's just a careless attitude. If somebody likes to drink and party, they'll probably enjoy drinking and partying in the wilderness. If somebody enjoys drinking and partying, frequently has free weekends, possesses the means and money to travel far to do so, and has friends with free weekends who are also willing to trek into the wilderness... well... they're probably not high school or college age kids. This is of course also ignoring the fact that an adult is anybody 18 years of age, because if you look at it like that, I would guarantee that at least 90% of people trashing fossil creek are adults.
On the other hand, people like my parents consider anybody under 35 young. Under these terms, yes, most of the trash at fossil creek is thanks to young people. That is still unfair and completely misleading, however, because "young people" automatically infers that it is 21 year old careless punks like myself causing everything.
Either way, any sort of stereotyping, whether or not there seems to be any hint of truth to it, upsets me. No, Mexican people aren't ruining Phoenix, Muslims don't all want to bomb the US, and kids aren't singlehandedly ruining your wilderness experience. It's a bummer when you can't just point a finger and be done with it, isn't it?
And for the record, I contain my marijuana aroma to only the most secluded spots.