Municipalities across the nation are incorporating natural resource preservation principles into their zoning ordinances. They are not doing so uniformly, but their collective progress is impressive. Some local legislatures describe the protection of the natural environment as a specific purpose of zoning. Localities may protect open space in zoning districts by adjusting applicable density, lot size, and setback restrictions. For example, conservation zoning districts permit only private land uses that are compatible with the natural environment, while agricultural zoning districts preserve agricultural land for farming purposes and open space.  To read more click: http://lawprofessors.typepad.com/land_use/2014/10/using-zoning-to-protect-the-environment-an-excerpt-from-protecting-the-environment-through-land-use-.html.