what does the man's failure to 'build a fire' symbolize?

The man did not respect his environment. The "old timer at Sulphur Creek" is mentioned quite a few times. The man did not heed his warnings and in the end was unable to build a fire. The symbolism is the weakness of man amidst the power of nature. Man is able to adapt to his environment to a point. If he fails to respect nature's signs and rhythms, he will be defeated.