Population Ecology in Conservation and Management What brings about declines? How do we identify and deal with causes?

Generalized risk assessment steps 1. Hazard Identification 2. “Dose-response” 3. “Exposure assessment” 4. Risk characterization

Hazard Identification Effects of all hazards on populations: changes in reproduction or survival Hazards are not just anthropomorphic may be entirely natural and/or mediated by human actions Hazards may interact with one another outcome may be unexpected

Types of hazards to consider Habitat alteration (by people) Introduced species: Disease Contaminants Predators Competitors Herbivores

More on disease…. Historically, not considered major issue Increasingly implicated in recent pop- ulation crashes of various species Likely to be of increasing importance in the future

Example: Laysan Island

Proper identification of hazard is critical! You will need: Detailed knowledge of natural history Info on distribution of both hazard and species of interest Experimental field studies to identify true causation

“Dose-response” Concept from traditional toxicology Applicable to population-level risk assessment Populations differ in susceptibility across space and through time

Exposure Assessment Is the target population actually “exposed” to the hazard? Again, borrowed from toxicology Applications to population ecology Need to identify and characterize factors that really are associated with problems

Risk Characterization Is the threat really a problem? Best addressed with field studies that include a carefully planned experimental design Modeling can also be used for limited purposes

Examples of field studies The good: brown tree snakes and native birds on Guam The bad: introduced predator effects on nene on Hawaii The ugly: fox predation of rock wallabies

Other Considerations in Risk Assessment How big are the populations? What is the species’ range? What is the life history? What are the genetic issues, if any? How much do populations interact? What are mutualists, if any?

Other considerations…. What about variation? demographic environmental Dan Rosenberg Clair de Beauvoir

Some modeling tools Elasticity/sensitivity analyses Comparing potential outcomes of management strategies Model population dynamics to explore possible links between factors and population behavior

Summary All risk assessments incorporate the same basic steps We can begin to assess impacts with deterministic population analyses We can evaluate management strategies or assess risk using stochastic analyses These are Population Viability Analyses