Implementation of cumulative effect assessments in maritime spatial planning: insights from two North Sea case studies

Résumé fourni par la source

The implementation of an ecosystem-based Maritime Spatial Planning (MSP) requires a holistic understanding of the interactions between maritime activities and marine ecosystems. Cumulative Effects Assessments (CEA) are essential for providing planners with such knowledge. However, despite multiple national and international initiatives, their application in MSP still needs to be further developed. Significant challenges remain: methodological limitations such as the integration of the scale of pressures caused by each activity or the relative nature of the risk of cumulative effects calculated by most tools. In this context, we developed enhancements to the global framework for Cumulative Effects Assessments. To better integrate the scales at which different activities affects the environment, for each group of activities and category of pressures, we attributed a magnitude value approximating the proportion of the environment affected by the activity. We then integrated these magnitudes in an existing CEA tool to improve the binary relationship between activities and pressures. We also used these weighted relationships in combination with the sensitivities of ecosystem components to define an unsuitability value for activities: the unsuitability of an activity is higher wherever ecosystem components are highly sensitive to whichever pressures the activity emits at high magnitude. We completed a CEA applying these improvements in two North Sea case studies, respectively at local and sea-basin scales. Drawing on insights from these studies, we present conclusions regarding the application of CEA for MSP at local and sea-basin scales: weighting pressures by their magnitude refines the calculation without altering the overall distribution of results. The unsuitability of activities provides relevant information to organize activities sustainably. Finally, regarding scales, the use of a finer resolution, where possible, provides accuracy and reliability of results for the CEA that is most useful in the case of geographically restricted areas.

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