It is the policy of the Congress and the Secretary that visitor services in park areas may be provided only under carefully controlled safeguards against unregulated and indiscriminate use so that visitation will not unduly impair park values and resources. Development of visitor services in park areas will be limited to locations that are consistent to the highest practicable degree with the preservation and conservation of the resources and values of the park area. It is also the policy of the Congress and the Secretary of the Interior that development of visitor services in park areas must be limited to those as are necessary and appropriate for public use and enjoyment of the park area in which they are located.