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

Population Ecology in Conservation and Management

What brings about declines?

How do we identify and dealwith 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 anthropomorphicmay be entirely natural and/or mediated by human actions

Hazards may interact with one anotheroutcome may be unexpected

Types of hazards to consider

•Habitat alteration (by people)

•Introduced species:

•Disease•Contaminants

PredatorsCompetitors

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 hazardand species of interest

•Experimental field studies to identifytrue causation

“Dose-response”

•Concept from traditional toxicology

•Applicable to population-level riskassessment

Populations differ in susceptibilityacross 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 factorsthat really are associated with problems

Risk Characterization

Is the threat really a problem?

Best addressed with field studies thatinclude a carefully plannedexperimental design

Modeling can also be used for limitedpurposes

Examples of field studies

The good:brown tree snakes and native birdson Guam

The bad:introduced predator effects on neneon 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 Dan Rosenberg

Clair de Beauvoir

Some modeling tools

•Elasticity/sensitivity analyses

•Comparing potential outcomesof management strategies

•Model population dynamics to explore possible links betweenfactors and population behavior

Summary

All risk assessments incorporate thesame basic steps

We can begin to assess impacts withdeterministic population analyses

We can evaluate management strategiesor assess risk using stochastic analyses

These are Population Viability Analyses