Bjoern and I are just back from a two-week tour of Iceland, including hiking with a group around the desolate highlands in the middle of the country. The 330,000 population is mainly around the coast, where the sea makes the temperature a bit more conducive to life. A cold desert looks a lot like a hot desert except for the temperature and the fact that in Iceland the thin layer of moss on a lava field has taken a thousand years to grow; the footpath-clearing parties of central Iceland do not have a tough job.
The hiking was with a group of 10 other German speakers and an excellent tour guide (Susanne, working for Arinbjoern Johannson tours - I am a little bit in awe of her and would also recommend this tour to German speakers who like this sort of thing). We hiked 20km or so per day with packs and stayed in huts with no electricity and running water only from a tank fed by a pump, which needed to be watched in case it ran dry and lost suction. We slept in sleeping bags in one room. The huts had food caches but we also collected mushrooms and salad and one day caught fish. (This was all very hard work, it would be impossible to travel while living off the land to a meaningful extent).
Iceland is actually pretty suitable for extended semi-wild hiking. For one thing it is all so dead that the rivers are safe to drink, and even the lakes are clean as tap water. B and I did some laundry in the lake and it smelled perfectly OK to us, while a Swiss river would leave it smelling of river (I shivered for hours afterward though). For another, it is cold - I wore shorts once or twice in high summer, and mostly wore all the clothes I had brought and shivered. This is better for hiking than heat. Noticeably, tourists wear their North Face or Jack Wolfskin outdoors gear while the Icelanders just put on an Icelandic wool sweater over a few layers of thermal vest. The first would-be settlers of Iceland, the family of a Viking called Floki sometime in the 800s, arrived in high summer and thought it was great but then endured an unusually terrible winter and went home as soon as they could.
Iceland's geothermal is quite impressive, especially when you are just driving through a valley and see billows of steam from a random farm or pool. People use this to set up "hot pots", basically swimming pools with at least one 40 degree C tub. The rules are quite strict about using these: you WILL take a gender-segregated communal shower completely naked first and use the soap on hair, armpits, crotch and feet. It was a bit weird to get naked in front of the people I had been hiking with but basically worth it. Anyway they would have laughed at me if I hadn't.
I now have a much sharper enjoyment of being somewhere with running water, private showering and sleeping quarters, English speakers, electricity and internet. But I am glad to have gone for a bit, and after being over 50km from the next human beings, hiking in Switzerland feels a bit tame (though it is awfully convenient to have pubs instead of potable rivers and edible berries).