Regionally Significant Habitats of Concern
Habitats of concern were identified based on three criteria. The first criterion recognizes regionally at-risk, or priority conservation habitat types such as oak savannas, grasslands, and wetlands. These habitats are at risk because they formerly covered much more extensive areas, and they tend to be declining in quality where they still remain. The second criterion recognizes the extraordinary and unique value of riverine islands and delta areas. The third criterion recognizes known habitat patches providing unique or critical wildlife functions. To qualify as a habitat of concern, an area only needs to meet one of the three criteria (See Metro, 2002).
Metro identified and ranked riparian resources by rating landscape features according to their contribution to specific riparian functions. These functions include: microclimate and shade; stream flow moderation and water storage; bank stabilization, sediment and pollution control; large wood and channel dynamics; and organic material sources. Landscape features were evaluated to determine the level of function they provide primarily based on the distance from water bodies recommended in current scientific literature. The scores are additive for any given landscape feature. Scores range up to 30, a higher score indicating greater ecological function (Metro, 2002).
Wildlife Habitat Resources
Metro developed a separate model to identify and rank wildlife habitat resources in the region. Rankings were based on habitat characteristics including: habitat patch size, habitat interior area, connectivity and proximity to water resources, connectivity and proximity to other patches, and habitats of concern and habitats for unique and sensitive species. For each characteristic scoring criteria were developed. The scoring range for each criterion was determined by natural breaks in the data, as identified by the Jenkins method. The scores are additive and range up to 12 points, representing high wildlife resource value. However, for all areas surveyed and ranked, the highest score was 10 points and the lowest was 2 points (Metro, 2002).