Ecological Integrity Assessment
Terrestrial ecosystems are complex combinations of plants, animals, soils, and other abiotic factors that provide critical ecological benefits, such as water quality improvement, flood control, carbon storage, climate regulation, aesthetic enjoyment, and biodiversity support. But their complexity also makes it challenging to characterize their ecological condition. Assessing ecological condition has become important, as broad scale stressors such as land use, invasive species and climate change alter the processes and benefits that ecosystems provide. For that reason, ecologists have pursued a variety of methods to track and respond to declines in ecosystem condition, including ecological integrity methods.
Ecological integrity concepts provide valuable information for assessing ecosystem condition and management effectiveness, and are an important component of ecologically based monitoring. Ecological integrity can be defined as “the structure, composition, and function of an ecosystem operating within the bounds of natural or historical range of variation.” Ecological integrity is a broad and useful endpoint for ecological assessment and reporting. The goal of an ecological integrity assessment (EIA) is to provide a succinct assessment of the current status of the composition, structure, processes, and connectivity of a particular occurrence of an ecosystem type. Ecological integrity is interpreted in light of reference conditions based on natural ranges of variation, and with a practical interpretation of site information that can inform management decisions and guide conservation and restoration activities.
An Ecological Integrity Assessment (EIA) is an approach to systematically rate the current ecological integrity of an occurrence of a plant association or ecological systems. The goal of an EIA is to provide a succinct assessment of the current status of the composition, structure, processes, and connectivity of a particular occurrence of an ecosystem type, interpreted in light of reference conditions based on natural ranges of variation, and with a practical interpretation that can inform management decisions and guide conservation and restoration activities. The EIA is a multi-metric index of ecological integrity based on measures 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 EIA is designed to document degradation of key biotic and abiotic attributes along a continuum from reference standard to highly degraded. The ratings are aggregated into a total score. A rating or score for individual metrics, as well as an overall index of ecological integrity, are communicated with the scorecard. 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 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 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. Washington Natural Heritage Program ecologists in collaboration with NatureServe and ecologists from other State Natural Heritage Programs have developed a standardized EIA for assessing wetland and riparian condition (include hyperlink when report is done) across the United States. EIAs for uplands ecosystems is also being developed and will be posted here when completed.
EIAs may be completed for a number of purposes, including:
- Determine the range in integrity of an ecosystem type based on sampling occurrences within a landscape or watershed.
- Identify occurrences with the highest levels of integrity within a jurisdiction. These occurrences may then be further reviewed for their conservation value or as reference benchmark sites.
- Prioritize occurrences for conservation/management actions. Ratings are helpful both as absolute ratings (best anywhere) and as relative ratings (best of what we have).
- Track status of occurrences over time. After a site is protected and/or put under management, there is a need to know whether the integrity of the occurrence is staying the same or changing. Cost-effective, reliable measures of integrity are needed.
- Contribute to information on conservation status, such as NatureServe’s ranking method. Knowing how many occurrences are in good condition is an important guide to the overall conservation status or at-risk status of an ecosystem.
- Prioritize field survey work. If some ecosystem types have no know occurrences with high integrity, they may be the focus of additional survey work.
- Assess restoration/mitigation efforts. Information on the ecological integrity of reference benchmark sites (excellent condition) or a full range of reference sites (excellent to poor) can help set performance standards for restoration and mitigation, to ensure that ecosystems are restored to desired conditions.
- Inform species population viability assessments. When species populations are closely linked to specific wildlife habitats or ecosystem types, the occurrence rank of the habitat type may serve as a guide for the species viability ratings. For example, increasing the ecological integrity of shrub-steppe stands improves the odds that species dependent on that ecosystem will do well.
EIA Online Training
An online EIA training presented by Natural Heritage Program staff in 2022, now modified into self-guided online training modules, is available at the link below. This is a great place to start if you are interested in learning more about EIA methodology and applications.
Besides the training modules, users are strongly encouraged to read the relevant technical resources below before implementing the EIA in order to fully understand the assumptions built into the method.
