These Information Notes will support careful consideration of how, for a particular development, potential impacts that are considered low risk could be safely retired from further detailed consideration within Environmental Impact Assessments (EIA), where available evidence supports this approach. Ocean Energy Systems-Environmental (OES-Environmental) has set out a general process for risk retirement1,2 but for developments in Welsh waters, risk retirement should always be discussed between developers and Natural Resources Wales (NRW) at the pre-application stage. In the context of these Information Notes, risk retirement implies that all potential impacts are included for consideration at the project scoping stage, and that following a review of the evidence some impacts may be ‘scoped out’ of any further detailed assessment to focus EIA on key significant impacts3. In all cases, potential impacts should be acknowledged in EIAs, with evidence-based justifications describing why particular impacts could be ‘scoped out’ of further detailed assessment.
Monitoring benthic and pelagic habitat change at several MRE developments has provided some information about potential effects from single device and small array deployments. The purpose of these monitoring programmes has generally been to detect changes to the local environment after deployment of an MRE device. Monitoring programmes are often designed to detect whether there is a change before and after installation, rather than to detect why a change is happening and this has made it difficult to understand the cause-effect relationships that result in such changes (Dannheim et al. 2018). It is, however, possible to gather experience and understanding from similar industries such as oil and gas and offshore wind farms. Studies of habitat change at offshore wind farms, for example, suggest that new infrastructure can cause changes in habitat that influence local biodiversity and ecosystem resilience over time (Causon and Gill 2018). However, these effects will be highly dependent on the type of MRE development, as the characteristics of habitats are dependent on physical characteristics such as depth, flow speeds, wave exposure, and seabed substrate type. The natural variability in benthic and pelagic habitats in highenergy environments has only been described by a few studies and is not well characterised (Kregting et al. 2016).