Informing conservation with an approach combining scenario modeling and spatially explicit risk-assessment

Background/Question/Methods

Wildlife managers must identify stressors that threaten persistence of populations and then try to reduce risk posed to population viability.  Experimental field research provides clear evidence connecting management actions to outcomes.  However, field research can be challenging when working with species of conservation concern, due to permitting issues and fear of doing harm to endangered populations, sampling issues and lack of statistical power, or time limitations when a population is rapidly decreasing or decisions regarding protection status are pending.  Scenario modeling can be used within an ecological risk assessment framework to assess threats to species populations and their habitats while avoiding issues encountered with experimental field research and to examine potential tradeoffs associated with alternative management actions.  We used an approach combining scenario planning and ecological risk assessment to map and quantify risk to population persistence for three rare prairie species on a military base in Washington State, USA.  We examined five alternative management scenarios with varied levels of treatment for an invasive shrub (Scotch broom; Cytisus scoparius) and locations of restrictions on military training.

Results/Conclusions

Of the management scenarios considered, only a scenario with year-round restrictions on use of off-road vehicles, digging, and camping enforced in all potential habitat reduces risk to the species.  Decreased risk is focused primarily in two patches of prairie habitat, indicating stringent restrictions need not be applied to the entire base.  However, one area is not easily accessed by two of the three species considered, suggesting reintroductions to suitable, but inaccessible habitat may play an important role in management of these species.  Our analyses suggest changes in land use and management that might improve habitat for rare species, with options for minimizing cost to military training.  Because the proposed approach relies on hypothetical management scenarios and uses a model flexible in data requirements to provide spatially explicit output, it can be used to inform management of rare species in diverse land planning processes and will be especially useful when management decisions must be made under time or cost constraints.