Strategies for assessing cumulative ecological risks

Assessing and managing the ecological risks from multiple stressors is beco ming increasingly important as our environmental and regulatory focus moves from managing point sources to one of managing and trading risks from mult iples sources over large geographic areas. There are important corollaries to this shift in focus and scale, one is the increased role and importance of non-chemical stressors in shaping and controlling ecological systems, th e fact that these categories of stress are, for the most part, not regulate d under the traditional legislative mandates, that we have limited knowledg e regarding the interaction of chemical and non-chemical stressors, that at large scales we are faced with the integration of and trading of risks to multiple resource categories. This trend of increased attention to regional -scale environmental issues requires the development of new analysis and in terpretive strategies and highlight the need for a systematic framework for addressing the ecological effects of multiple stressors at regional ecolog ical scales. We propose that such a framework have three essential properti es: it be risk-based; it be effects driven; and it have the flexibility to be used in both a retrospective and prospective manner. While several appro aches have been proposed we believe that an ecological risk assessment fram ework satisfies these criteria, has been used successfully in regional asse ssments, and can readily be modified and adapted to serve a wide variety of problem settings.