Visitors planning to camp in the park must obtain permits and be assigned campsites. This is necessary to facilitate control of camper services, as well as to reduce the danger of forest fires. Campers and other visitors who fail to comply with park regulations are subjects to expulsion from the park. Do not feed park animals. If you want to participate in animal feeding, look for feeding schedules posted near feeding sites. This is your park. Protect it by reporting any violation of park regulations. Enjoy your visit.

This is necessary … line 2. What is the closest meaning of the word necessary?