Agricultural zoning, including forestry zoning, is the most common method of resource land preservation used by local governments. Such zoning restricts land uses to farming and livestock, other kinds of open space activity, and limited home building. Hawaii and Oregon require the use of agricultural zoning by all local governments that have prime agricultural farmland. The most important element of agricultural zoning is the extent to which it restricts the intrusion of new, nonfarm uses into established agricultural areas. Four general approaches to resource-land-use zoning are: nonexclusive use zoning, voluntary agricultural districts, exclusive use zoning, and agricultural buffers. Case/Example: Agricultural zoning of Hawaii and Oregon. Source/Reference: Nelson and Duncan, 1995, pp. 51-54.