Common open space, particularly perimeter buffer yards, containing existing attractive or unique natural features, such as streams, creeks, ponds, woodlands, specimen trees and other areas of mature vegetation worthy of preservation may be left unimproved and in a natural state. As a general principle, the preservation of undeveloped open space in its natural state is encouraged. A landowner and/or developer may make certain improvements, such as the cutting of trails for walking or jogging and the provision of picnic areas.