There are many reasons that may cause a species to be at risk. Biologists and planners must know what factors are limiting the distribution and abundance of a given species. In development of Habitat Conservation Plans biologists and planners need to assess these limiting factors and development means to adequately eliminate or mitigate their effects. Species that are particularly vulnerable to extinction fall in to one or more of the following categories of species (as described in R.B. Primack. 1995. A Primer of Conservation Biology. 277 pgs. Sinauer Associates Inc., Sunderland, Massachusetts.):

• narrow geographical ranges (e.g. desert slender salamander)
• narrow habitat or niche (e.g. black swift)
• only one or a few populations (e.g. California condor)
• population size is small (e.g. Morro Bay kangaroo rat)
• low population densities (e.g. wolverine)
• population size is declining (e.g. mountain yellow-legged frog)
• need large home range (e.g. mountain lion)
• large body size (e.g. black bears)
• not effective dispersers
• low genetic diversity

• habitat loss modification, and fragmentation
• influences of exotic species
• increased spread of diseases
• effects of contaminants

Center scientists are conducting research to better understand how such factors may be influencing declining species and subsequently what can be done to mitigate such impacts. Examples of current research that are contributing to our knowledge about certain species at risk include:

• Applying a bioassessment and monitoring framework for public lands and trust resources in coastal and estuarine habitats of the United States
• Distribution and impact of perennial pepperweed on wildlife refuges in California
• Giant garter snake habitat conservation plan -- ecosystem initiative
• Epizootiology of avian cholera and its control in migratory birds
• Pitcher's thistle dynamics: population and seed predation