In 1971 my wife and I signed up for a Sierra Club "High Light" trip, two weeks in the upper elevations of Sequoia and Kings Canyons National Parks. Most of the time we were well above tree line (highest point: 13,200 feet), with duffel carried by mules, about 60 people all together including staff.
At every camp site the leaders instructed volunteers on building two shielded privies, one for men and one for women. When we moved on, the privies and all other evidence of our camping were buried and cleaned well enough so that nobody could tell that a group had camped there. The staff provided excellent education on the environment and how to leave no visible trace.
I believe that was the last year the Sierra Club trips were so large. The main reason they went to smaller groups was that it was a bit intimidating for a lone hiker to encounter an army of 60 or so.
But even where there are no trees, it is possible to do your business without leaving a smelly mess.
