Natural Quality

The objective of monitoring the Natural Quality is to assess the effects of modern civilization on the integrity of wilderness ecosystems, with a focus on plants, animals, air and water, and ecological processes. The Wilderness Act defines wilderness as an area that “is protected and managed so as to preserve its natural conditions” and that these areas should be free from the effects of “an increasing population, accompanied by expanding settlement and growing mechanization” (sections 2(c) and 2(a), respectively). Human-caused changes to wilderness ecological systems can be intentional or unintentional. While managers may have control over some impacts to natural ecosystems in wilderness, many threats come from external sources outside of their jurisdiction (e.g., air pollutants and nonindigenous species). In contrast to the Untrammeled Quality, which monitors actions that manipulate or control ecological systems, the Natural Quality monitors the effects on wilderness ecosystems from actions as well as external forces. While this quality encompasses all the naturally occurring species, physical resources, and ecological functions and processes in wilderness, practical limitations require that a relatively small but significant subset of possible measures are monitored.

For the Natural Quality, a single monitoring question provides the broad context and four indicators provide the structure for this monitoring (as summarized in table 1.3.1).

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3.1 Monitoring Question

A single monitoring question is used to monitor the Natural Quality: What are the trends in the natural environment from human-caused change?

This monitoring question assesses the trends in natural wilderness ecosystems that result from human-caused threats occurring since designation of the area as wilderness. Importantly, this monitoring question seeks to distinguish between natural variability, which is integral to all ecosystems and does not degrade wilderness character, and human-caused change. In wilderness, the primary goal is to allow ecosystems to function and change without impacts or interference from modern civilization; therefore, the Natural Quality should not be used to set a target to maintain a particular ecological state or condition. In addition, this monitoring question does not include actions taken to restore ecological systems in wilderness. There are several reasons for not including these actions, including: (1) actions are tracked in the Untrammeled Quality, not the Natural Quality that tracks effects; (2) restoration actions are highly site-dependent and no single national protocol to measure such actions and their effects has been developed; (3) restoration actions typically assume static or historical ecological conditions contrary to wilderness as a place where human-determined states are not appropriate; and (4) the effects of restoration actions should eventually show, with monitoring, as an improving trend in the Natural Quality.

Four indicators assess a range of ecosystem components, structures, and functions in wilderness: (1) plants, (2) animals, (3) air and water, and (4) ecological processes. Practical and conceptual constraints mean that not everything important to wilderness ecosystems can be included in this monitoring. Likewise, not all ecological data currently collected by scientists are relevant or necessary to include in WCM. The measures under each indicator are not all encompassing; rather, the measures are selected because they are known human-caused threats to the indicators. Part 2, section 3.6, provides a detailed discussion of the criteria and process used for selecting measures under the Natural Quality; this section should guide local units considering the use of locally developed measures under this quality.

3.2 Indicator: Plants

This indicator focuses on threats to indigenous plant species and communities. Indigenous plant species (also referred to as native plant species) and plant communities are an essential biological component of natural wilderness ecosystems. Indigenous plant species and plant communities are those that evolved in an area and therefore have intrinsic value within a wilderness. In addition, they are critically important to the entire ecosystem by providing food and habitat to indigenous animals, preventing soil erosion, adding soil nutrients, and maintaining the local environmental conditions and biodiversity.

3.2.1 Measure: Acres of Nonindigenous Plant Species

This measure assesses the total number of acres, or the estimated percentage of acres, occupied by selected nonindigenous plant species in wilderness. The introduction and spread of nonindigenous species (also referred to as non-native, alien, or exotic species) is the second leading cause of plant and animal species endangerment and extinction worldwide (Lowe et al. 2000). Although many nonindigenous species are present throughout the United States, invasive nonindigenous species (i.e., those species that increase quickly in abundance and distribution) are a particular threat to wilderness character and are therefore the focus of this measure.

This measure was selected because nonindigenous plants may directly and indirectly alter the composition, structure, and function of natural communities in significant ways by degrading or eliminating habitat for native plant and animal species, and causing multiple cascading effects throughout the entire ecosystem. The adverse impact of these species on the Natural Quality of wilderness character is significant. Because of established concerns about nonindigenous species, this measure is relatively simple and cost effective to monitor.

This measure is required for all Forest Service wildernesses. A 5-percent or greater change in the number of measured or estimated acres, or any change in defined “percentage occupied” categories, will result in a change in trend for this measure. An increase in the acreage occupied by nonindigenous species corresponds with a degrading trend.

Refer to part 2, section 3.2.1, for detailed guidance on data sources and compilation protocols, analysis, data adequacy, and interpreting the threshold for meaningful change.

3.3 Indicator: Animals

This indicator focuses on threats to indigenous animal species and communities. Indigenous animal species (also referred to as native animal species) and animal communities are an essential biological component of natural wilderness ecosystems. Indigenous animal species and communities are those that evolved in the area and therefore have intrinsic value within a wilderness. Additionally, they are critically important to the entire ecosystem by providing food and habitat to other animals, digesting plant material and thereby making nutrients available in the soil for plants to use, scavenging carcasses of dead animals, and contributing to a wilderness ecosystem in many other ways.

3.3.1 Measure: Index of Nonindigenous Terrestrial Animal Species

This measure is an index that assesses the geographic distribution and estimated impact of selected nonindigenous terrestrial animal species. Nonindigenous animal species generally occur inside a wilderness because of human influence, such as intentional and unintentional introductions and transplants. Once nonindigenous species become established outside a wilderness, they may spread naturally or disperse into that wilderness. Nonindigenous animals include livestock that intentionally graze in wilderness, as well as feral domesticated animals, such as feral livestock, horses, goats, and pigs. Examples of nonindigenous terrestrial insects include: Asian longhorned beetle, emerald ash borer, gypsy moth, and hemlock woolly adelgid. Terrestrial pathogens and diseases are included in this measure because even though they are not animals, they are not considered plants either and creating a separate measure for them is not warranted. Examples of terrestrial pathogens and diseases that would be included in this measure are sudden oak death, chronic wasting disease, and whitenose syndrome.

This measure was selected because nonindigenous terrestrial animals, insects, and pathogens and diseases may significantly alter the composition, structure, and function of natural communities by degrading or eliminating habitat for indigenous species, and causing multiple cascading effects throughout the entire ecosystem. The adverse impact of these species on the Natural Quality of wilderness character is significant.

Units are required to select either this measure or the following measure, Index of Nonindigenous Aquatic Animal Species, or may select both measures if relevant to the individual wilderness. A 5-percent or greater change in the measure value will result in a change in trend for this measure. Once there are five measure values, the threshold for meaningful change will switch to regression analysis, and statistical significance will determine the trend in the measure. An increase in the measure value corresponds with a degrading trend.

Refer to part 2, section 3.3.1, for detailed guidance on data sources and compilation protocols, analysis, data adequacy, and interpreting the threshold for meaningful change.

3.3.2 Measure: Index of Nonindigenous Aquatic Animal Species

This measure is an index that assesses the geographic distribution and estimated impact of selected nonindigenous aquatic species (NAS), including amphibians, fish, crustaceans, mollusks, gastropods, aquatic insects, and aquatic pathogens and diseases. NAS are typically introduced into a given wilderness by anthropogenic vectors, although species introductions may also have originated outside of a wilderness and the species subsequently moved into the wilderness by upstream or downstream movement. Aquatic pathogens and diseases are included in this measure because even though they are not animals, they are not considered plants either and creating a separate measure for them is not warranted. Examples of an aquatic pathogens and diseases that would be included in this measure are: whirling disease, iridoviruses, and chytrid fungus.

This measure was selected because nonindigenous aquatic animal species may alter the composition, structure, and function of natural aquatic communities, and adversely impact indigenous species, reduce biodiversity, and degrade natural aquatic ecosystems.

Local units are required to select either this measure or the preceding measure, Index of Nonindigenous Terrestrial Animal Species, or may select both measures if relevant to the individual wilderness. A 5-percent or greater change in the measure value results in a change in trend for this measure. Once there are five measure values, the threshold for meaningful change will switch to regression analysis, and statistical significance will determine the trend in the measure. An increase in the measure value corresponds with a degrading trend.

Refer to part 2, section 3.3.2, for detailed guidance on data sources and compilation protocols, analysis, data adequacy, and interpreting the threshold for meaningful change.