Cumulative Effects in Marine Ecosystems: Scientific Perspectives on its Challenges and Solutions
Accurately accounting for the cumulative effects of impacts, however, can be difficult. Human activities produce a range of stressors that may interact and have greater impacts than expected, compounding direct and indirect effects on individuals, populations, communities and ecosystems. In addition, natural variability in ecosystem processes may affect the manifestation of resulting impacts. Assessment of cumulative effects on marine ecosystems requires extensive scientific research that directly tests the effects of multiple stressors; however, our knowledge of cumulative effects is largely based upon studies of single stressors on single ecological components that are combined to estimate the effect of multiple stressors. Therefore, advancing cumulative effects knowledge and assessments requires embracing the complexity, uncertainty, and natural variation in ecosystems and applying the best available science to evaluate and predict cumulative effects. In this review we discuss four components of cumulative effects science and application: (1) how cumulative effects manifest in ecosystems as a result of multiple human activities; (2) challenges in applying scientific knowledge in cumulative effects assessment, including defining spatial and temporal scales, baselines, reference points, indicators, and identifying significant changes in the face of uncertainty and natural environmental variability; (3) models and tools that have been developed to assess cumulative effects; and (4) priorities for science and management of cumulative effects. Conservation of marine ecosystems and support for sustainable development requires using primary research, models, and tools in an integrated, adaptive ecosystem-based framework to address cumulative effects.