but it's a fairly safe inference that whatever it was dissuaded Chris from walking down to the park service road and over the bridge there.
The film seems to jump track to his toxicity from the veg, yet surely in real life he must've given it a go to try to march out before having to quit, turn around, due to injury.
my essential 50
http://www.imdb.com/list/ls056413299/

Remember, he was not planning on being in Alaska probably beyond summer-fall yes?
That's right. It doesn't appear in the movie, but Chris had promised Wayne that he would be back in Carthage by mid-August to help with the harvest.
He died from eating the wrong vegetation. Otherwise he probably could've lasted another few weeks before marching back out.
In the film, this is indeed the case, but not in real life. Although the
hedysarum alpinum
plant's seeds were not particularly nutritious, they were not harmful, either, and there's no evidence he ate them in any great quantity - apparently the malaise he felt after a meal with them (which could well have been caused by something unrelated, like coccidia or giardia) discouraged him from eating the rest of the ones he had collected. No poisonous plants are to be found in the area, but more importantly, no sources (other than fish) of needed fats, and after his rice was gone, not enough carbohydrates. So he was starving to death; a type of starvation called "rabbit starvation" from the fact that you could stuff yourself with rabbit, but because it is so lean, your body uses more energy to digest it than it metabolizes from the meat, so it's possible to starve to death on a full stomach. Chris caught other game, but these too were lean and low in calories and almost totally deficient in carbs.
Chris wanted to leave in July, so as to make it back to South Dakota for August. But something other than the high water in the Teklanika stopped him. On the bus (in real life) he left a note saying he was injured, and "for God's sake please remain and save me." We don't know what the injury was (broken bones can be ruled out, but soft tissue injuries would not have been detected on autopsy after the fact), but it's a fairly safe inference that whatever it was dissuaded Chris from walking down to the park service road and over the bridge there. He might have had a sprained ankle or torn cruciate ligament or something similar, or a shoulder injury, as speculated by Ron Lamothe, which would have made his trek through the boggy and unstable terrain much more difficult than usual. Perhaps he put it off until he was clearly too weak to try.
But I don't think he could have hiked out a few weeks later. He was much too frail by the beginning of August to do any serious hiking; when his injury occurred, we don't know.

Yes & no. From the movie, I feel like he wanted nature to tackle & challenge him. Remember, he was not planning on being in Alaska probably beyond summer-fall yes? I think he wanted to, & opted to, throw himself at nature pure & simply, to take what nature would dish back.
So while yes, he was naive, I wouldn't say he was off his rocker as it were.
Hell, he rode surging rapids sans helmet. That's beyond f'd up compared to living in bear territory.
He died from eating the wrong vegetation. Otherwise he probably could've lasted another few weeks before marching back out.
my essential 50
http://www.imdb.com/list/ls056413299/