The PNW Habitat Classification Systems (PHaCS) Database is a component project of the Northwest Environmental Data-Network, an information portal sponsored by federal, state, tribal and non-governmental entities to improve the quality, quantity, and availability of regional fish, wildlife, and water data. It is hosted by the Northwest Habitat Institute in partnership with the National Biological Information Infrastructure.

Habitat classification systems differ greatly throughout the PNW depending on agency, organization, or monitoring group, often complicating data-sharing and collaboration. The PHaCS database attempts to crosswalk and establish threads of commonality from the different habitat classifications within the region. Cross-walking, a process of mapping elements from one standard or schema to another based on definitions or semantics, has been used to establish connections between different Habitat Classification Systems and the Interactive Biodiversity Information System (IBIS), developed by the Northwest Habitat Institute and used as the common reference system for this database. The database tool provides, when available, information about the habitat classification systems in the PHaCS; the habitat categories and definitions of the systems; associated and complementary systems; and IBIS habitat types, structural conditions, and key environmental correlates, including cross-walks from each system to IBIS.