Parcel yield (density, building area, lot area, or floor area ratio). For any parcel containing protected land, density, lot area, building area, or floor area ratio shall be determined by applying the natural resource protection and density calculations referenced in § 139-158 of this chapter and § 73-11.1 of the Willistown Township Environmental Protection Ordinance. Density shall be no greater than that which the zoning, subdivision and environmental protection regulations would permit.