Chehalis Basin Fisheries Task Force
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EDT (Ecosystem Diagnosis and Treatment)
The EDT model was selected for use based on an extensive review of assessment tools that have been employed for salmon.
Our review addressed the following questions:
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How might EDT be used to address some of Washington's salmon problems? |
EDT was developed by Mobrand Biometrics to provide a practical, science-based approach for developing and implementing watershed plans. The EDT method consists of three components:
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Conceptual Framework—a way of organizing information to describe a watershed ecosystem in order to apply scientific principles to the understanding of that ecosystem |
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Analytical Model—a tool used to analyze environmental information and draw conclusions about the ecosystem |
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Step-by-Step Procedure—a procedure that explains how to apply the conceptual framework and analytical model to develop plans that achieve goals. |
The general approach for comparing existing and desired conditions is called the Patient-Template Analysis (PTA). This approach compares existing conditions of the diagnostic populations and their habitat (patient) with a hypothetical potential state (Template), where conditions are as good as they can be within the watershed. The Template is intended to capture the unique characteristics and limitations of the watershed due to its combination of climate, geography, geomorphology, and history.
The diagnosis is performed by comparing the Patient and Template to identify the factors or functions that are preventing the realization of objectives. The diagnosis can be qualitative or quantitative, depending on the type and quality of the information used to describe the ecosystem. Regardless, the diagnosis forms a clear statement of understanding about the present conditions of the watershed as related to the diagnostic species.
The population abundance of different species depends on the quantity and quality of habitat in an area. By linking species’ population abundance to varying habitat conditions, EDT predicts the responses of species’ populations to varying habitat conditions.
How does EDT link population levels to habitat conditions?
The analytical model is the tool used to analyze environmental information and draw conclusions about the ecosystem. The model incorporates an environmental attributes database and a set of mathematical algorithms that compute productivity and capacity parameters for the diagnostic species.
What is the geographic scale of an EDT analysis?
EDT can be applied to several geographic scales. It may be applied to a region, such as the Columbia Basin that spans Washington, Oregon, Idaho, and Montana. It may be applied to WRIAs (collections of watersheds), of which there are 62 in Washington. Or, it may be applied to habitat conditions and species’ populations in individual watersheds.
Yes. EDT has been used to develop fish and wildlife plans for the Grande Ronde and Deschutes rivers in Oregon; the Clark Fork River in Montana; and the Cowlitz, Yakima, and Nisqually rivers in Washington. The co-managers are evaluating the utility of EDT for establishing recovery goals for listed species in Puget Sound and the Lower Columbia; the Northwest Power Planning Council used EDT to evaluate options for the Columbia River Multi-Species Framework Plan.
How might EDT be used to address Washington’s salmon problems?
EDT can be used to analyze existing habitat conditions in a watershed and to predict the amount of increase or decrease in numbers of salmon as these habitat conditions are changed. If several restoration activities were being contemplated in a particular watershed, EDT provides a way to quantify the probable results of these activities in terms of numbers of fish that would likely be produced.
Our review led us to the following conclusions:
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Applicability. EDT is the only broadly tested analytical tool that integrates habitat conditions across time and space to predict, in terms of fish production, productivity, and diversity, the benefits of alternative management actions.
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Feasibility. EDT has been broadly applied throughout the states of Washington, Oregon, and Idaho. The flexibility of the methodology, including the ability to incorporate data of varying degrees of quality, have proven invaluable under a under a wide variety of conditions
These attributes, among others, have led the NWPPC to specifically identify EDT as one of “the three types of analytical approaches will provide subbasin planners with an indication of where efforts for habitat improvements could be focused, how those efforts relate to populations at greatest risk of extirpation, and the future status of populations under alternative management scenarios.” 1 (note: the Cumulative Risk Initiative and ICBEMP Bayesian Belief Network were the two other approaches identified).