Recognizes that cities coterminous with, and comprised solely of, an island in qualifying counties have unique and valuable qualities that must be preserved. Recognizing the importance of preserving these qualities, as well as the continual changes that accompany population growth, the legislature finds that these island cities must have the authority to determine the residential densities, within the confines of properly accommodating growth, that are best suited to retain the agricultural, rural, residential, and historic character enjoyed by the residents.