Application of Threshold Concepts to Ecological Management Problems: Occupancy of Golden Eagles in Denali National Park, Alaska

  • Mitchell J. Eaton
  • Julien Martin
  • James D. Nichols
  • Carol McIntyre
  • Maggie C. McCluskie
  • Joel A. Schmutz
  • Bruce L. Lubow
  • Michael C. Runge
Chapter

Abstract

In this chapter, we demonstrate the application of the various classes of thresholds, detailed in earlier chapters and elsewhere, via an actual but simplified natural resource management case study. We intend our example to provide the reader with the ability to recognize and apply the theoretical concepts of utility, ecological and decision thresholds to management problems through a formalized decision-analytic process. Our case study concerns the management of human recreational activities in Alaska’s Denali National Park, USA, and the possible impacts of such activities on nesting Golden Eagles, Aquila chrysaetos. Managers desire to allow visitors the greatest amount of access to park lands, provided that eagle nesting-site occupancy is maintained at a level determined to be acceptable by the managers themselves. As these two management objectives are potentially at odds, we treat minimum desired occupancy level as a utility threshold which, then, serves to guide the selection of annual management alternatives in the decision process. As human disturbance is not the only factor influencing eagle occupancy, we model nesting-site dynamics as a function of both disturbance and prey availability. We incorporate uncertainty in these dynamics by considering several hypotheses, including a hypothesis that site occupancy is affected only at a threshold level of prey abundance (i.e., an ecological threshold effect). By considering competing management objectives and accounting for two forms of thresholds in the decision process, we are able to determine the optimal number of annual nesting-site restrictions that will produce the greatest long-term benefits for both eagles and humans. Setting a utility threshold of 75 occupied sites, out of a total of 90 potential nesting sites, the optimization specified a decision threshold at approximately 80 occupied sites. At the point that current occupancy falls below 80 sites, the recommended decision is to begin restricting access to humans; above this level, it is recommended that all eagle territories be opened to human recreation. We evaluated the sensitivity of the decision threshold to uncertainty in system dynamics and to management objectives (i.e., to the utility threshold).

Keywords

Golden Eagles Aquila chrysaetos Utility threshold Ecological threshold Decision threshold Occupancy modeling Structured decision-making Adaptive management Uncertainty Wildlife disturbance 

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Copyright information

© Springer Science+Business Media, LLC 2014

Authors and Affiliations

  • Mitchell J. Eaton
    • 1
    • 2
  • Julien Martin
    • 1
    • 3
  • James D. Nichols
    • 1
  • Carol McIntyre
    • 4
  • Maggie C. McCluskie
    • 4
  • Joel A. Schmutz
    • 5
  • Bruce L. Lubow
    • 6
  • Michael C. Runge
    • 1
  1. 1.Patuxent Wildlife Research CenterU.S. Geological SurveyLaurelUSA
  2. 2.Southeast Climate Science CenterU.S. Geological SurveyNCSU RaleighUSA
  3. 3.Florida Fish and Wildlife Conservation CommissionFish and Wildlife Research InstituteSt PetersburgUSA
  4. 4.National Park ServiceFairbanksUSA
  5. 5.Alaska Science CenterU.S. Geological SurveyAnchorageUSA
  6. 6.Natural Resource Ecology LaboratoryColorado State UniversityFort CollinsUSA

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