DETERMINING THE BIOLOGICAL SIGNIFICANCE OF CHANGES IN PREDICTED HABITAT VALUES FROM THE CALIFORNIA WILDLIFE HABITAT RELATIONSHIPS SYSTEM

The California Wildlife Habitat Relationships System (CWHR) computerized database can predict the effects of habitat changes to wildlife communities by calculating differences in species composition and habitat values between two habitat conditions. Five different categories representing varying levels of change significance were used to evaluate how impact assessments might differ under a hypothetical scenario. The categories were: (i) habitat unsuitable for one habitat situation; (2) CWHR's predicted difference in overall average habitat suitability; (3) difference of at least one CWHR rating class for overall habitat suitability; (4) difference in overall average habitat suitability value of 25% or more; and (5) difference in overall average habitat suitability value of 50% or more. These categories resulted in significantly different(P< 0.003) effect levels (Negative and Positive Effects, Uneffected) for all wildlife groups (birds, mammals, reptiles, and all taxa) except amphibians. Predicted effects were mostly influenced by model habitat suitability ratings. Of the five categories, Habitat Unsuitable and Habitat Rating Class Difference are the most biologically-based, while Habitat Unsuitable is easiest to verify because it is based on differences in species lists only. However, of the five categories, Habitat Unsuitable resulted in the fewest number of species predicted to be negatively or positively effected.