The reason for this answer is because the passage/article explains how the Smokey Bear campaign had helped prevent fires that are caused by human carelessness.
The decrease in forest fires is a result of the Smokey Bear campaign.
Explanation:
Because the passage tells us the need to reduce forest fires was in part motivated by the Smokey Bear campaign as "The campaign has been successful-since its inception, the average area lost annually to forest fires has dropped from 22 million to 4 million acres."
