Limiting your choice lenses is very therapeutic. You hear a lot of photographers pontificate about using only one lens for travel. In fact, there are endless forum discussions on this very topic. While this is a great exercise to help develop your skills as a photographer, one focal length is far too limiting. Take into account that you may be visiting a place you may never travel to again. Having multiple angles of view will help you capture scenes more effectively. And besides, why have an interchangeable lens camera if you're only going to use one lens?
Due to the nature of Galen Rowell's mountaineering inspired photography, he was known for using lightweight Nikon gear. Very often, he had his trusty 24mm prime along with a telephoto zoom (different points of time using a 80-200mm, and later the 70-200mm). Galen obviously had a diverse selection of gear for his professional work, but the thought of limiting adventure photography to two lenses inspires me. I have found, in my own practice, that one wide with a telephoto prime works well. Through trial and error, I've also found that 24mm is the most versatile wide angle for landscape photography.
Even though a two lens line-up has served me well, I have struggled to pack as light as Galen did. I like to shoot medium and large formats quite often. A 35mm camera will typically serve as my secondary camera. So a typical trip will include my Pentax 645, Fotoman 6x9, or Fotoman 4x5, along with a Nikon 24mm and medium telephoto (85 to 135 range). I haven't fully embraced the telephoto zoom as I've found 85mm to be a great focal length for tight shots in the mountains. Though I do think that the 70-200mm f4G sounds very promising.
Galen's work has been a great inspiration to my taste in photography. While I looked to what equipment he used to help guide my early gear choices, I am fully aware that gear does not make the photographer. You can not simply use the same tools as the greats and get the same quality images. But it is very encouraging to see that one of my photo idols used simple gear to capture his vision. Galen Rowell's photography is proof that fancy equipment and resolution are not needed for stunning images.