Many of the wonderful outdoor areas that you'll be exploring in Zion and Bryce Canyon national parks are quite isolated, especially in the backcountry at Zion. Not long ago, the rule was to "leave only footprints"; these days, we're trying to do better and not leave even those. It's relatively easy to be a good outdoor citizen -- pack out all trash, stay on established trails, be especially careful not to pollute water, and, in general, do your best to have as little impact on the environment as possible. Some hikers carry a small trash bag to pick up what others may have left. As the park service likes to remind us, protecting our national parks is everyone's responsibility.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.