As I remember the film, it was death by poison mushroom, risked due to starvation — I feel like it was a death depicted over maybe two weeks. I remember the overall stay being quite bearable.. until the winter hit, and everything went wrong; and death came swiftly and without mercy
But regardless the movie depicts it as a fairly slow, very painful, and a fairly pathetic death (alone, weak, with lots of regret and little to show for it), but still 90% of the movie was him running around in gorgeous nature shots and small towns.
Actually, I believe (at least in the movie) it came from eating a type of poisonous berry that he naively mistook for a very similar-looking nonpoisonous berry.
But regardless the movie depicts it as a fairly slow, very painful, and a fairly pathetic death (alone, weak, with lots of regret and little to show for it), but still 90% of the movie was him running around in gorgeous nature shots and small towns.