Each person has their own reason for isolation. By physically escaping to nature, people find less social stimuli with which they must cope, and turn their attention to more environmentally oriented stimuli. This coping behavior is commonly known as displacement. This happens when one is dissatisfied with one's environment and feels a crowding affect. Therefore, the individual or group displaces themselves from the stressors experienced utilizing the above mentioned locations.
Security is certainly a social aspect to discuss.
For many people, experiencing nature and its benefits provides security in many ways. Some feel security solely for the fact that they are out in the wilderness and there is a great likelihood, depending on how far out they go, that no one is around for miles. This is a great reason to escape urban pressures and fears. Another type of security comes from knowing that one has left behind the social pressures to perform and one can act as natural as one feels. Along with this observation is the fact that many people also feel they are judged in their every day social life.