I was just thinking about skiing and the impact it has on the environment and I couldn't help thinking that Heli-Skiing and Sledding are terrible for the environment.
For both you are going into the wilderness potential disturbing the wildlife. For both you are using a humongous amount of fuel to get skiers up to the top of their lines.
Compared to ski-resorts where the impact is concentrated in one area, the efficiency of ski-lifts have to be much more efficient than heli-skiing and sledding. But you do have the factor of resort lodging, trash produced and the number of cars to bring people to the hill but that is simply because of the sheer volume. On a per-skier basis it is much worse to go backcountry skiing using a helicopter or a sled than it is to use a resort.
Obviously, skinning does not fall into this category and has the lowest impact out of all the others.
tldr: If you want to save the environment don't go heli skiing or use a sled to go backcountry skiing.