Integration of Effects-Based and Stressor-Based Approaches into a Holistic Framework for Cumulative Effects Assessment in Aquatic Ecosystems

As the density of development increases, there is a growing need to address the cumulative effects of project developments on the environment. In Canada this need has been recognized in legislation whereby new project developments that require an environmental assessment under the Canadian Environmental Assessment Act are required to address the cumulative effects of proposed project activities relative to the existing environmental condition. Unfortunately, existing stressor-based and effects-based approaches to environmental assessment do not adequately address cumulative effects as defined under the Act when used in isolation. However, elements from each approach can be conceptually incorporated into a holistic cumulative effects assessment framework. Key framework components include: (1) an effects-based assessment to determine existing accumulated environmental state, (2) a stressor-based assessment to predict potential impacts of new development relative to the existing environmental state, (3) post-development monitoring to assess the accuracy of impact predictions and to provide an avenue for adaptive management, and (4) decision-making frameworks to link scientific information to public opinion and managerial action. The key advantage of this framework is that it provides a more holistic, systematic approach for incorporation of ecological information into a scientific and management framework for cumulative effects assessment.