Workshop to compile evidence on the impacts of offshore renewable energy on fisheries and marine ecosystems (WKCOMPORE)

This report provides a comprehensive analysis and evaluation of the current state-of-the art in available evidence and science concerning the economic, social, and ecological impacts of offshore wind farms (OWF) and floating offshore wind farms (FLOW) on fisheries in the Baltic Sea, Celtic Seas, and Greater North Sea. It describes the observed and potential economic, social, ecological and cumulative impacts of OWF and FLOW, with a focus on the scope of the existing evidence base, data and methods to assess impacts, and mitigation options to avoid or reduce unwanted impacts. Overall, the workshop to compile evidence on the impacts of offshore renewable energy on fisheries and marine ecosystems (WKCOMPORE) highlights the need for additional high-resolution data, comprehensive assessments, and stakeholder involvement to better understand and mitigate the impacts of OWF and FLOW on fisheries and marine ecosystems. Specific ‘key findings’ arising from WKCOMPORE include:

Economic and Social Impacts:

• The assessment of economic and social impacts of OWF and FLOW requires high-resolution data on vessel positions, fisheries catch and effort, fisheries economics, and social data. However, existing data are often insufficiently detailed and not well-linked, making comprehensive impact assessments a challenge.
• Both ex-ante (before) and ex-post (after) methods are used to assess these impacts. Studies have shown that OWF and FLOW can negatively affect income, fishing grounds, catching opportunities, and operating costs. It was concluded there are generally more studies reporting on negative impacts than positive benefits.
• Context factors such as the type of OWF and FLOW, development phase, and adaptive capacity of fisheries influence the nature and magnitude of impacts. No studies were found on trade-offs between economic impacts on fisheries and OWF and FLOW.

Ecological Impacts (benthos and higher trophic levels):

• OWF and FLOW development phases have known or predicted local impacts on commercially fished species, but no population-level assessments were identified. The requirements for such analyses are, however, described.
• Assessing the potential impact of offshore wind farms (OWF) (fixed and floating) on commercial species requires a detailed understanding on how related human operations and the pressures they exert cause environmental effects leading to population-level impacts across spatial and temporal scales.
• Combined pressures caused by OWFs, climate change and other human pressures give rise to cumulative risks, demanding integrated environmental assessments such as cumulative effects assessments (CEA) and multi-scale management strategies.
• · The trait-based framework (TAFOW) applied in the current study links OWF-induced state changes to population characteristics and response traits, enabled species vulnerabilities to all phases of OWF life cycle to be assessed.
• · A total of 34 commercial species were assessed in the North Sea, Celtic Sea, and Baltic Sea, using the TAFOW framework, which identified that sediment resuspension was likely to be the most impactful state change, with highest vulnerabilities noted in the Celtic Sea driven by changes in larval dispersal and predator-prey interactions.
• The present study revealed that from the 34 commercially most important fisheries resources assessed; herring, great scallop, and monkfish are the most vulnerable species across the three regions.
• Trophic interactions and recruitment survival of fisheries resources are particularly vulnerable to pressures that are exerted by operational OWF.
• It was concluded there is insufficient evidence to directly assess and quantify the effects of OWF and FLOW on the Western Baltic herring stock, although there is no direct specific evidence to suggest existing OWF sites are impacting Western Baltic herring stocks.
• Baltic Proper harbour porpoise will likely be directly affected during all stages of offshore renewable energy development, and especially by the introduction of underwater noise. Given the aforementioned critically low population size, even moderate impacts are to be avoided.

Cumulative Impacts:

• WKCOMPORE evaluated existing methods and models with the potential to assess cumulative impacts of OWF and FLOW. Some models and tools were deemed suitable or had potential through further development to quantify cumulative impacts and test mitigation options.
• An important distinction is made between CEA models/ tools based on risk assessment framework approaches which are useful in identifying ecosystem components in areas at highest risk, from ecosystem models which can quantitatively assess the interactions between specific aspects of windfarm developments and fisheries in support of operational management advice.
• The models/ tools evaluated in the present study (in terms of their operational utility), classified as ecosystem models, offering the greatest utility to support operationally CEAs were; VMStools, FishSET, Community Profiling Tools. DISPLACE, OSMOSE and EwE/ Ecospace.
• The importance of developing case studies to demonstrate the practical application of available strategic risk-based assessment frameworks (such as BowTie, FEISA, ODEMM and SCAIRM) should be linked explicitly with the outputs of quantitative (mechanistic) ecosystem models where possible.
• It was concluded there is no single CEA or ecosystem model/ tool available to provide a comprehensive assessment of all component interactions at a social, economic and ecological level, between windfarm developments and fisheries. The application of a combination of CEA and ecosystem models/ tools is therefore recommended for assessment purposes.
• The current study concluded the need to increase focus on exploring long time-series fisheries and environmental data (>10 years) to better describe and understand the spatial/temporal dynamics of core fishing areas and climate effects in response to offshore windfarms.

Hydrodynamic and Pelagic Ecological Effects: (foodweb, productivity and lower trophic levels):

• Most commercial species with a pelagic life stage within an ecoregion will overlap in spatial distribution with dynamic cables associated with OWF and FLOW throughout the time that the cables are in the water column (construction, operation and decommissioning).
• Interactions between species and cables leading to responses will relate to either direct energy emissions, physical effects and/or indirect ecological effects.
• Only during OWF and FLOW operations will dynamic power cables create energy emissions sufficient to represent potential stressors to commercial pelagic fisheries species.
• The timing of exposure to energy emissions will be determined by the operational characteristics of the cables and the length of time that species use the pelagic environment around dynamic power cables.
• An approach to assess the impacts of dynamic power cables on commercial fish species is proposed.
• Turbines create atmospheric wakes, and underwater structures modify currents and stratification. These changes affect primary production and support communities of filter feeders.
• Offshore wind farms (OWFs) provide stepping stones for species dispersal across unsuitable environments, benefiting both indigenous and non-indigenous species (NIS), especially benthic species with long larval pelagic phases. However, the relative influence of OWFs compared to other artificial substrates remains unclear. All NIS observations in OWFs had previously been reported from the region.
• Floating OWFs are likely to harbour non-indigenous species (NIS) and facilitate their spread through turbine transport between ports and wind farms. Evidence from similar structures supports this, but direct studies on floating OWFs are lacking.
• Impressed Current Cathodic Protection (ICCP) may enhance calcifying organism growth in biofouling communities, with potential regional variations due to environmental factors. Confidence in this effect is however low, as it lacks robust empirical support.
• Galvanic Anode Cathodic protection (GACP) may impact biofouling communities through metal toxicity effects, but confidence is low due to limited studies.
• Elevated temperatures on cooling water pipes and dynamic cables in OWFs might influence biofouling community composition and growth rates. However, evidence remains inconclusive, and further studies of this pressure is required.
• OWF sound pollution may impact biofouling organism behaviour, with variability across species. The relationship between sound and invertebrate behaviour in OWFs is poorly understood, and its ecological significance remains uncertain.
• Underwater structures can directly affect ocean dynamics by causing friction and flow obstruction. This increases turbulence, reduces current speed, and weakens water stratification up to 400 meters behind the structures. Enhanced mixing induced by OWFs may increase nutrient availability in the euphotic zone, promoting local phytoplankton production in the near-field of the structures. This effect applies primarily to fixed-bottom foundations.
• Reduced wind speeds within atmospheric wakes decrease wind-driven currents and ocean mixing, strengthening water stratification on scales up to 100 km away from the OWFs. Large wind farms create vertical circulation patterns (upwelling and downwelling). This can increase primary production around and decrease it inside wind farm areas.
• The currently planned OWF installation in the North Sea can induce changes in hydrographic conditions that might alter spatial and temporal dynamics in the marine ecosystems. In a published model scenario considering the installation of 120GW in the North Sea, local ecosystem changes could reach up to 10% not only at the OWF side but on a regional scale.

Mitigation measures Maritime Spatial Planning (MSP):

• Maritime (or Marine) Spatial Planning (MSP) provides a way to allocate areas to OWF & FLOW and other human activities, and through subordinate planning processes, instruments and supporting procedures contribute to the identification and implementation of management measures, including mitigation options.
• Multi-use and co-use approaches seek to enable co-existence between users and activities.
• Stakeholder involvement, engagement and co-design help enable development of mitigation options that are technically, economically, politically, socially and ecologically feasible, and supported, or at least accepted, by stakeholders.