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Ecological Integrity Assessment (EIA)

Ecological integrity can be defined as “the structure, composition, and function of an ecosystem operating within the bounds of natural or historic range of variation.” An Ecological Integrity Assessment (EIA) rates the current ecological integrity of an occurrence of a plant association or ecological system.  NatureServe and the Natural Heritage Network have developed the EIA as an index of ecological integrity based on metrics of biotic and abiotic condition, size, and landscape context. Each metric is rated by comparing measured values with the expected values under relatively unimpaired conditions (i.e., operating within the natural range of variation). The ratings are aggregated into a total score or a scorecard matrix. A rating or score for individual metrics, as well as an overall index of ecological integrity, are communicated with the scorecard.

The EIA can be applied to multiple spatial scales (e.g., landscape or site-scale) and with a variety of data types (e.g., GIS or field-based). EIAs are developed for individual ecological systems using a three level approach to identify a suite of metrics, including Level 1 (remote sensing), Level 2 (rapid ground-based), and Level 3 (intensive ground-based) metrics.

In summary, the EIA framework provides a standardized currency of ecosystem integrity across all terrestrial ecosystem types. This information can then be used for setting conservation priorities, identifying restoration strategies, and monitoring the effectiveness of conservation actions.

The Washington Natural Heritage Program, with funding from the Washington Department of Fish and Wildlife, has developed EIAs for 67 of Washington’s 99 Ecological Systems. Relying primarily on literature sources and best professional judgment, we identified indicators and metrics for assessing ecological integrity by:

  1. Outlining a general conceptual model that identifies the major ecological attributes, providing a narrative description of declining integrity levels based on changes to those ecological attributes, and introducing the metrics-based approach to measuring those attributes and assessing their levels of degradation.
  2. Using ecological classifications at multiple classification scales to guide the development of the conceptual models, allowing improved refinement of assessing attributes, as needed.
  3. Using a three level assessment approach – (1) remote sensing, (2) rapid ground-based, and (3) intensive ground-based metrics – to guide development of metrics.  The 3-level approach is intended to provide increasing accuracy of ecological integrity assessment, recognizing that not all conservation and management decisions need equal levels of accuracy.
  4. Identifying ratings and thresholds for each metric based on “normal’ or “natural range of variation” benchmarks.
  5. Providing a scorecard matrix by which the metrics are rated and integrated into an overall index of ecological integrity.

Most of the EIAs have been peer-reviewed. However, field validation and calibration has yet to occur for any of the EIAs.  The Washington Natural Heritage Program will update the EIAs as field testing and/or additional peer review merit such changes.

Related links:

Washington Natural Heritage Program -
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Washington Dept. of Natural Resources, PO Box 47014, Olympia, WA 98504-7014