Washington Gap Analysis

Washington Gap Analysis

What is Gap Analysis?     View a movie about Gap Analysis.

Gap Analysis is a process of identifying areas of high conservation priority. It is designed to be a proactive approach to conservation. Gap relies on information about current landcover and terrestrial vertebrates to identify habitat types and species that are poorly represented on reserves.

Our land cover map was made from satellite Thematic Mapper (TM) images from 1991. We delineated areas of similar vegetation using the satellite images as a guide. Our minimum mapping unit (i.e., the smallest patch we mapped) was 100 hectares (or about the size of Green Lake, for those familiar with Seattle).

The distribution of breeding vertebrates was modeled using known range limits and habitat association. Programs written for Arc/Info select suitable habitat for each species, and then refine it by geographic and elevation limits based on knowledge of each species.

The resulting maps were combined to provide maps showing centers of diversity, which can be overlaid with land ownership maps to determine areas of need for preserving all species. The point of Gap Analysis is to try to determine critical habitat before it becomes 'critical', and before its fauna becomes endangered.


Predicted distribution maps

The predicted vertebrate distribution maps are included in the "Maps" section on the The NatureMapping Program web site. The distribution narratives have been summarized.

The Washington Gap Analysis GIS range maps can be downloaded, from the Washington State Department of Fish and Wildlife Web site.

Printed Volumes

The final printed volumes are available for purchase through the Washington Cooperative Fish and Wildlife Research Unit.
  • Volume 1: Land Cover of Washington State: Description and Management, 260pp.
    Description of the actual land cover of Washington State mapped using 1991 satellite (TM) imagery. The 31 vegetation zones within the state are the major framework for the analysis. The analysis for each zone (e.g., Ponderosa Pine Zone) includes a description of the natural land cover, the current land cover, and its conservation status. Maps of generalized land cover and conservation status categories are included (3 - 24x36" color maps).

    Volumes 2-4 include narratives for each species include a brief description of habitat requirements and how the distributions were modeled. On the facing page, a map of the predicted distribution with known locations (museum records or, for birds, the Seattle Audubon Society's Breeding Bird Atlas data) is provided. These atlases contain the most current and detailed distribution maps for terrestrial vertebrates in the state.

  • Volume 2: Amphibians and Reptiles of Washington State: Location data and predicted distributions, 146pp.
  • Volume 3: Terrestrial Mammals of Washington State: Location data and predicted distributions, 304pp.
  • Volume 4: Breeding Birds of Washington State: Location data and predicted distributions, 538pp.
    (Published by the Seattle Audubon Society - out-of-print)
  • Volume 5: Gap Analysis of Washington State: An evaluation of the protection of biodiversity, 192pp.
    A detailed analysis of the conservation status of land cover and vertebrate species (excluding fish) in the state. Analyses are presented for each of the 31 vegetation zones and the entire state, and provide a landscape context for biodiversity conservaiton and natural resource management (9 color maps).

  • Washington State Land Cover Manual: Metadata and Data Dictionary. CD-ROM requires ArcInfo. (To accompany the Digital Land Cover Map of Washington State and available only with purchase of Land Cover volume.

    The project was funded by the United States Geological Survey (USGS) Biological Resources Division, through the Washington Cooperative Fish and Wildlife Research Unit at the University of Washington. To read a more detailed account about Gap go to the National Gap homepage.

    Washington Gap Analysis Project


    Washington Cooperative Fish and Wildlife Research Unit
    University of Washington Box 355020
    Seattle, WA 98195-5020
    (206)543-6475

    The Washington Gap Analysis team:
    Kelly Cassidy, Ph.D. Now lecturing at Washington State University, Pullman
    Karen Dvornich (206) 616-2031 vicon@u.washington.edu
    Christian Grue, Ph.D. (206) 543-6475 cgrue@u.washington.edu
    Michael Smith, M.S. Now with the US Fish and Wildlife Service