Rating impacts in a multi-stressor world: A quantitative assessment of 50 stressors affecting the Great Lakes

Sigrid D.P. Smith, Peter B. Mcintyre, Benjamin S. Halpern, Roger M. Cooke, Adrienne L. Marino, Gregory L. Boyer, Andy Buchsbaum, G. A. Burton, Linda M. Campbell, Jan J.H. Ciborowski, Patrick J. Doran, Dana M. Infante, Lucinda B. Johnson, Jennifer G. Read, Joan B. Rose, Edward S. Rutherford, Alan D. Steinman, J. David Allan

Research output: Contribution to journalArticlepeer-review

59 Scopus citations


Ecosystems often experience multiple environmental stressors simultaneously that can differ widely in their pathways and strengths of impact. Differences in the relative impact of environmental stressors can guide restoration and management prioritization, but few studies have empirically assessed a comprehensive suite of stressors acting on a given ecosystem. To fill this gap in the Laurentian Great Lakes, where considerable restoration investments are currently underway, we used expert elicitation via a detailed online survey to develop ratings of the relative impacts of 50 potential stressors. Highlighting the multiplicity of stressors in this system, experts assessed all 50 stressors as having some impact on ecosystem condition, but ratings differed greatly among stressors. Individual stressors related to invasive and nuisance species (e.g., dreissenid mussels and ballast invasion risk) and climate change were assessed as having the greatest potential impacts. These results mark a shift away from the longstanding emphasis on nonpoint phosphorus and persistent bioaccumulative toxic substances in the Great Lakes. Differences in impact ratings among lakes and ecosystem zones were weak, and experts exhibited surprisingly high levels of agreement on the relative impacts of most stressors. Our results provide a basin-wide, quantitative summary of expert opinion on the present-day influence of all major Great Lakes stressors. The resulting ratings can facilitate prioritizing stressors to achieve management objectives in a given location, as well as providing a baseline for future stressor impact assessments in the Great Lakes and elsewhere.

Original languageEnglish (US)
Pages (from-to)717-728
Number of pages12
JournalEcological applications : a publication of the Ecological Society of America
Issue number3
StatePublished - Apr 1 2015

Bibliographical note

Publisher Copyright:
© 2015 by the Ecological Society of America.


  • Aquatic
  • Cumulative impact mapping
  • Ecological risk assessment
  • Environmental threats
  • Expert elicitation
  • Expert judgment
  • Questionnaire
  • Weight of evidence


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