If there's one thing that the Appalachian Trail Conservancy takes seriously, it's their Leave No Trace policy. This is the main reason why dogs are a concern for trail clubs, and why they're regulated so harshly. Leave No Trace, or LNT, is a code of outdoor ethics designed for the minimization of one's footprint through various rigorous conservation tactics. There are seven rules: 

1. Plan ahead and prepare: bring the necessary tools and equipment for leaving no trace, these include such tools as a fire pan and a poop spade
2. Travel and camp on durable surfaces: campers should find places where vegetation is already absent to minimize damage to the environment
3. Dispose of waste properly: avoid contaminating natural water sources and bury human waste to prevent the spread of disease to wildlife
4. Leave what you find: minimize environmental impact when you can
5. Minimize campfire impacts: keep fires small and contained, using preexisting fire rings when possible
6. Respect wildlife: observe animals from far off so as to not spook them or disturb their natural patterns
7. Be considerate of other visitors: the forest is not only shared by animals, but also other hikers

All of these rules are built upon the foundation of "leave the place as you found it."