Toward process-based causality indicators for assessing and monitoring ecological impacts of offshore wind energy: a benthic perspective

Offshore wind energy (OWE) is rapidly emerging and expanding in several countries worldwide. A current challenge is understanding the ecological-causal processes underlying OWE environmental impacts to determine appropriate indicators for baseline assessment and follow-up monitoring. Here, we reviewed the ecological impacts and screened parameters that can serve as process-based indicators of causality for assessing and monitoring changes in benthic environments associated with OWE development. To this end, we first conducted a global literature review (73 articles) to compile evidence on OWE impacts on benthic environments. Next, based on the assessed evidence, we designed conceptual-qualitative ecosystem models to clarify the ecological-causal processes connecting OWE pressures with their potential cascading effects. Lastly, we identified ecological parameters from the reviewed literature that could serve as indicators of the processes described by the models. As key results, we detailed the causal chain of OWE effects on benthic environments and proposed 32 indicators for assessing and monitoring impacts. We highlighted that the causal meaning of the indicators, from a process-based perspective, depends on considering biodiversity categorized by life-history traits, rather than relying on general parameters such as the total abundance of the benthic community. This includes classifying species into ecological functional groups that will signal distinct causal processes, such as noise pollution, organic enrichment, and changes in ecosystem functioning. Such a tool can be further applied in baseline and monitoring studies to guide Environmental Impact Assessment toward a process-based praxis that is more aligned with the principles of Ecosystem-Based Management.