When horsepackers attend the official LNT low-impact course, some of the points covered are:
1. To minimize the number of horses needed, use lightweight gear and carry only what you must.
- Tie horses to live trees only for a short while. Choose trees at least 8 inches in diameter, since they can withstand some root trampling and bark damage ("girdling").
- To prevent rope damage, place a gunny sack or wide, nylon strap between the tree and the rope.
- Never corral horses in a wet, boggy area or near a water source; the damage could be irreparable.
- Choose an area with a good breeze; it helps keep bugs at bay and makes for less pawing and stomping by irritated equines.
- Scatter all manure; ideally, carry it far from the campsite, then scatter.
- Use existing, high-impact camp sites whenever possible; they should be at least 200 feet from water sources and trails.
- In remote, fragile areas, spread out tents, avoid creating trails to and from popular areas like the kitchen site, and "naturalize" (cover scuffed areas with forest debris, for instance) before leaving.
- Carry horse feed to minimize the amount of vegetation nibbled.
2. Use a camp stove. If you build a campfire, do so atop mineral soil and scatter it afterwards, or use a fire pan.
But what to do about
- Manure that falls on the trail? Some LNTers advocate "diapers" for horses, an approach that doesn't appeal to most horsepackers.
- Erosion-caused ditches in trails frequented by horses? When you consider that your average half-ton horse or mule exerts pressures of up to 1,500 pounds per square inch per hoof, the potential for a long-lasting impact is obvious. Horseshoes place a shear force on soil and vegetation, and so don't help the matter. In some overly used areas, when the "trails" get too deep for horses to negotiate safely, outfitters create new paths alongside the old ones. These, too, eventually erode, and you have a series of ditches winding up a hillside. At this point, there's no simple solution to either dilemma, and the search for answers continues. t For long-term horse restraint, say, overnight, find an area with dry, hard ground or minimal groundcover. Erect a highline by stringing a rope a little more than head-high (the horses', not yours) between two large trees, and then tie the horses to the overhead rope. They'll be able to move about somewhat and won't be confined to one spot.
Source: Leave No Trace: Outdoor Skills
and Ethics: Backcountry Horse Use