Synthesizing and modeling interactions among environmental stressors in the Laurentian Great Lakes
Many environmental stressors can occur simultaneously in an ecosystem. However, their cumulative effects on ecosystem condition are difficult to predict, since stressors can be amplified or mitigated when they co-occur. We synthesized the incidence of stressor interactions in the Laurentian Great Lakes with a systematic literature review and structured expert elicitation. In the review, we searched pairs of stressors and interaction-related keywords with location, augmenting our results with recommendations from experts. The elicitation included discussion in focus groups and a follow-up survey. To explore the effects of stressor interactions on ecosystem condition holistically, we modified a spatial model of cumulative impact that additively combined the spatial distributions of 34 stressors.
In the literature, we found that authors discussed synergies in the majority of relevant studies, such as interactions of invasive mussels and climate change with other stressors, but full quantification of individual and joint effects were rare. In the elicitation, researchers particularly implicated nutrient loading in interactions, expecting synergies with invasive mussels, hypoxia, wetland loss, and climate change. Considering the effects of such interactions, conservative scenarios with our cumulative impact model showed that antagonisms strongly affected maps of relative stress. Currently, we are using conceptual models to explore key interactions and identify knowledge gaps, and we are incorporating the specific interactions from the review and elicitation into a new best-estimate map of cumulative stress to inform management and restoration efforts.