An assessment of ecosystem risks in the St. Croix National Scenic Riverway

Ecological risk assessment is recognized by many as an important conceptual tool in ecosystem management. The purpose of such a risk assessment is to identify those factors (stressors) that pose the greatest risk to ecosystem integrity so that environmental protection efforts can be focused on those strategies likely to yield the greatest reduction in ecosystem risk. If ec ological risk assessment is to move from the conceptual stage to the implem entation stage, new methodological tools must be developed and successfully applied. The purpose of this paper is to describe the application of a bas ic methodological risk assessment tool, first developed by the authors as p art of a case study involving Green Bay of Lake Michigan to the St. Croix N ational Scenic Riverway located in northwestern Wisconsin and east-central Minnesota. The information needed for conducting the risk assessment was provided by t he participants in a e-day workshop. The invited participants, who possesse d knowledge of the St. Croix ecosystem, identified through a group-consensu s process a list of stressors and a list of ecosystem values. They then ass igned numerical values to each stressor-ecosystem value pair that reflected the degree to which the given stressor contributes to ecosystem risk as me asured by the given ecosystem value. Based on this information, the analyti cal portion of the methodology was then used to rank the ecosystem risks (s tressors) when examined from several different perspectives: immediate impa ct, time-duration. and management activities. Regardless of the perspective taken, riverway development emerged as the most significant stressor.