Government Code § 51054

An instrument described in subdivision (a) of Section 51051 may contain, and the city or county in appropriate cases may require that it contain, a covenant against the extraction of natural resources or other activities which may destroy the unique physical and scenic characteristics of the land or a covenant against the cutting of timber, trees and other natural growth, except as may be required for fire prevention, thinning, elimination of diseased growth and similar protective measures, or for the harvest of trees in a manner compatible with scenic purposes.