Landscapes which appear to meet the National Register criteria must also retain integrity. Assessing a landscape’s integrity can be difficult when it involves a dynamic and complex interrelationship of cultural and natural resources. The elements of integrity must still apply, as with all historic properties, but special considerations have been identified to address the nature of changes to landscapes.

1.   Essential elements for integrity

Integrity is the ability of a property to convey its significance. The seven aspects of integrity are location, design, setting, materials, workmanship, feeling, and association. To retain historic integrity, a property will always possess several, and usually most, of these aspects, and essential physical features must be present. Examine integrity against essential physical features that were present during the historic period, and estimate the percentage of the historic landscape that is intact. Document any intrusions or missing elements. Note the relative importance of elements that have changed, keeping in mind that landscapes are necessarily dynamic in character.

The strength of historic landscape characteristics and the nature, extent, and impact of changes since the period of significance are important factors to consider in making the final decision about integrity. The landscape’s setting the environment or surroundings outside the property boundaries must also be assessed as an element of integrity. Note the presence of any large-scale natural features, such as mountains, desert, woodlands, and bodies of water, which can be important components of setting in a rural area. For rural landscapes, the relationship of landscape characteristics and integrity is complex, particularly in regard to design and materials. The dominant role of topography and natural features in rural landscapes requires some adjustment in applying the aspects of integrity to these resources. Changing land use or new vegetation may affect integrity of design or materials. While crop rotation or the introduction of contour plowing might have little effect, visible changes from field crops to orchards or from rangeland to irrigated fields could affect a rural landscape’s design integrity.

2.   Special considerations

In evaluating the integrity of historic landscapes, certain aspects may be more difficult to assess or they may present particular issues that should be considered.

a. Vegetation

Vegetation is generally very important to landscapes. Vegetation and the inherent characteristics of growth and evolution in plant materials present different issues related to change and integrity from those of buildings and structures. Plants grow and die, and the relationships among species vary over time due to differing growth patterns and land use. The integrity of a landscape’s vegetation may be considered reasonably intact if the original vegetation is present regardless of appearance or if substitute plantings essentially convey the landscape’s historic appearance. Original plants which have changed by natural processes do not normally cause loss of vegetative integrity, even if changes have resulted in visual alteration, such as the growth of trees originally planted in the nineteenth century around a state capitol. However, normal plant succession may destroy the most important qualities of a landscape, such as the natural regrowth of vegetation that obscures the raw scar of a hydraulic mining pit. Competing resource values in such cases can also lead to integrity loss for landscapes, if restoration of native vegetation in a park or removal of human traces in a wilderness area are valued over historic landscape preservation.

If original plant material is lost, a landscape can often maintain integrity if similar species convey the visual effect of original plantings, unless the property is significant for specific cultivars, such as an arboretum noted for hybridizing experiments. Otherwise, integrity can be preserved by comparable plantings of similar size, massing, color, and appearance as those present during the historic period. In other instances, if planting have value as examples of a design philosophy, or as physical markers, delineating boundaries or spaces, or as expressions of technology, such as spacing between plants, preserving the qualities that exhibit those values can maintain a landscape’s integrity.

Agricultural crops that were rotated historically or plantings that evolved during the historic period may offer more than one option for appropriate replacement plantings. Any replacements should preferably be the same or similar species, perhaps grown from seeds collected from the original plants if important genetically.

b. Continuing use

Change is often an inescapable part of a landscape. Natural processes may bring changes from plant growth, death, or succession; weathering; erosion; or soil deposits from flooding. The functioning and maintenance of properties in a landscape can also bring changes: new technologies, painting, road work, fence repair, and basic activities of a working property can have cumulative effects on a landscape’s appearance. The effect of continuing use on integrity depends to a substantial degree on the historic context, which should indicate the extent of integrity that can reasonably be expected.

A working landscape in which significant characteristics survive may maintain relative integrity despite some losses, when comparative properties in the same context are more altered. For example, a mining landscape still being worked may retain integrity if modern extraction methods and character are similar to those practiced historically, important physical elements remain, and comparable properties are less intact. Similarly, working transportation facilities can retain integrity if physical features essential to the property remain. A resurfaced road that has been slightly widened may retain integrity if its original guard rails, retaining walls, bridges, and alignment remain. An operating railroad can be expected to have had its rails and ties replaced periodically, and an abandoned railroad to have had both ties and rails removed, but a railroad line might retain relative integrity if the roadbed, associated features, alignment, and setting are intact.

c. Intrusions

Loss of integrity can come from new construction or incompatible land uses, such as modern mining or quarrying, the growth of residential subdivisions, new freeway construction, or other activities that reshape the land, disturb subsurface remains, introduce major visual intrusions, or interrupt the continuity of the historic scene. Changes outside the landscape’s boundaries can constitute intrusions when such changes introduce incompatible visible, audible, or atmospheric elements to the historic property, regardless of whether the setting itself is a contributing element. The effect of intrusions on a landscape’s integrity depends on the qualities that make the landscape eligible and must be assessed on a case-by-case basis. In some instances, large rural districts may be able to absorb changes that occur in relatively few or small isolated pockets within the landscape, but the cumulative effect of such changes must be considered.

d. Integrity vs. condition

Both integrity and condition must be addressed. Integrity is lost when a landscape’s important features are removed or altered, or when intrusions disrupt the landscape. Integrity can be maintained despite weathering or deterioration as long as essential physical features remain, although the condition could be poor.

For example, fences, watering troughs, and spatial arrangements may be intact in an abandoned overgrown pasture. Haul roads, camp sites, and stumps with springboard holes may identify a logged property despite a vigorous second growth of trees. A neglected garden could have both high integrity and poor condition. Similarly, landscapes containing ruins, rundown buildings, or abandoned roads that have deteriorated in place could possess integrity, while better-maintained areas still in use may have undergone substantial changes that destroy integrity.

Although not relevant to an evaluation, condition can be a consideration in determining treatment options, such as finding relocation and adaptive reuse more feasible for a building in good condition than for a ruin. National Register Bulletin 30 provides a detailed discussion of applying integrity standards to rural landscapes.