To preserve land resources and to mandate appropriate land use by designating zoning districts in accordance with the principles of City planning and to assure that adequate consideration is given to the impact of land use on the availability of land, water and other natural resources. "Land resources" are defined to include the quality of Boca Ciega waters and marine life, the shoreline and the ecologically important intertidal zone, including the mangroves, lands encompassed within the tidal flood zone, existing open space, required yards, green areas, the tree canopy and the ambient air quality and pollution in the City.