Leave No Trace, The Ethics of Outdoors
Outdoor recreations such as hiking or camping deals with the nature. Most of us would have limited sources, for there will be no 7-11 up there in the mountain or through the thick woods of forests, thus requiring us to be bring our own stuff to be consumed for the planned activity. Much of these would be food, you need to have energy out there with wildlife, unless you are superman.
Check out this video on Leave No Trace.