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Best Available Science


Under the state's Growth Management Act, local governments are required to use the best available science when reviewing and revising their policies and regulations on wetlands. However, there was no comprehensive synthesis or interpretation of the science for wetlands, and most local governments lack the resources to tackle such an undertaking.

The state departments of Ecology and Fish and Wildlife, with funding from the U.S. Environmental Protection Agency, initiated a project to develop a comprehensive synthesis of the science for wetlands. They hired Sheldon and Associates, Inc. and called on staff from the two agencies to produce a two-volume document on the science currently available on wetlands, their functions and management.

Volume 1 is the synthesis of the science regarding freshwater wetlands. Volume 2 translates the science synthesized in Volume 1 into guidance for local governments protecting and managing wetlands. Although the primary audience is local governments, both volumes are also valuable to any who have an interest in the protection and management of wetlands.

Update on Wetland Buffers: The State of the Science (October 2013)

Our scientific knowledge is continually increasing and changing and we recognized that the synthesis would need periodic updates. Much of the information presented is still valid, but the research in the last decade has provided new data to expand and clarify many of the conclusions made in the original synthesis. This is especially true for the information on the role of buffers in protecting wetland functions.

This update revisits the conclusions and key points concerning wetland buffers made in the 2005 synthesis described below.

 > Read more about the update

Volume 1:  A Synthesis of the Science

This is the first part of a two-part document. This volume contains a summary and synthesis of the literature relevant to the science and management of freshwater wetlands. The draft of Freshwater Wetlands in Washington State Volume 1: A Synthesis of the Science was reviewed by peer experts and the public.

Download the Document

Volume 2:  Guidance for Protecting and Managing Wetlands

Volume 2 translates the science into guidance for protecting and managing wetlands at the local level. To develop the guidance, the departments of Ecology and Fish and Wildlife worked with the Core Team that oversaw the project and whose members developed Volume 1. In addition, an advisory team of wetlands and planning staff from an assortment of local governments provided feedback on the guidance. Ecology also met with members of various organizations from the business and environmental communities. As with the synthesis of the science, Volume 2 underwent peer and public review so all those interested in the protection and management of wetlands had the opportunity to give feedback on the draft.

Download the Document

Related Documents

  • Wetland Rating Systems for eastern and western Washington - The rating systems, methods for categorizing wetlands using specific criteria, were updated in 2004 to reflect changes in our understanding of how wetlands function and how they are valued. The four rating system categories are intended to be used in developing standards for protecting and managing wetlands. Examples of protection standards include the width of buffers necessary to protect the wetland and the ratios needed to compensate for impacts to the wetland. We developed guidance for these protection standards as a part of Volume 2 of the Best Available Science project.
  • Guidance on Mitigation - Ecology updated its guidance on mitigation in 2006 to reflect changes in our understanding of wetland science and management.

  • Mitigation Resources -  Ecology has developed updated guidance on several mitigation topics, including site selection and use of alternative mitigation options (in-lieu fees, mitigation banks, and advance permittee-responsible mitigation).


Ecology's wetlands staff are available to work with local jurisdictions to develop effective wetland protection programs that include the best available science.


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