The wave energy industry is an emerging sector and, in comparison to more established industries, is a new user of maritime space. In order to realise the potential for wave energy to contribute towards EU renewable energy goals several technological and non-technological barriers need to be overcome. Many of the non-technological barriers are due to wave energy being at a relatively early stage in its development. Much attention has focused on the potential environmental impacts of wave energy and the burden of responding to this attention represents a significant barrier to the wave energy industry. As part of the SOWFIA project, an evaluation of experience related to the detection of environmental impacts at EU wave energy test centres along with information gained from environmental impact assessments produced for other similar renewable energy developments has been undertaken. This experience has been examined to understand key receptors of concern and methods used for detecting impacts, to produce effective methods for communicating the information gathered and to identify where possible, the type and magnitude of impacts which may be expected.
The key environmental receptors of concern for wave energy EIA include the physical environment (morphology, waves and current etc.) and flora and fauna as represented by marine mammals, seabirds, benthos and fish and shellfish.
There is a concern that removal of energy from waves and currents in the marine environment may result in significant environmental impact, whether to the marine ecosystem or to users of the marine space. Standard measurements such as wave buoys and ADCPs along with numerical simulations and more innovative measurement techniques can be used to study this issue Preliminary studies suggest that the magnitude of the non-local effects on the amplitude of waves or currents from projects studied so far are of order 10% reduction or less.
The introduction of additional anthropogenic sound into the marine environment is of concern for its potential to impact marine species which use sound for communication, navigation, finding prey and evading predators. Key aspects of assessing the impacts from introduced noise include identifying the baseline noise signal at the site of interest, the noise signature of the planned devices and the auditory sensitivity of species present. There is very limited experience in measuring noise emissions from wave devices with results which varied from being unable to distinguish the device noise from the ambient anthropogenic signal to having to limit measurements to very low sea states in order to avoid sensor saturation. Limited measurements from a deployed Pelamis device confirm that the signal varies with sea state and that the noise emitted would be detectable by marine species.
That all marine mammals are protected by national, European and/or international legislation is reflected in the fact that the impacts of wave energy on marine mammals was of significant concern at all the test centres in the SOWFIA project. There are a wide range of methods for monitoring marine mammals and the methods utilised will be determined by the questions to be assessed. Whatever methods are employed, it is critical to determine whether the survey design method will be able to detect an impact at an early stage. Limited existing experience within marine renewable energy developments suggests that marine mammals may avoid devices but further studies are needed. Experience with nets and static (but slack) fishing gear indicate that entanglement is a potential issue although the risk associated with wave energy devices is likely to be much lower than other ocean energy technology. This risk is potentially aggravated by the increased food arising from the FAD potential of WECs. Because of the highly mobile nature of marine mammals, cumulative effects from increasing MREI deployments are of a special concern which must be carefully considered primarily during SEA and secondarily in planning.
Seabird species are subject to various levels of regulatory protection and monitoring of seabird distribution and behaviour is a universal component of wave energy EIA. A special and key feature of this work is understanding the connectivity of development sites with SPAs which can be achieved only through tagging studies. The potential effects of marine renewable energy developments on birds can be summarised in three main categories: direct (collision, entrapment, displacement), indirect (noise, habitat enhancement, de facto MPAs), and cumulative. WECs have a much smaller above-water profile than wind turbines, and so are likely to have much lower risk of collision but the considerable underwater structure of some devices may provide an enhanced collision or entrapment risk. Entrapment of birds can be mitigated by covering openings, where possible, with a protective mesh. Migratory species and species that are restricted to foraging in specific habitats may be particularly vulnerable but sensible development planning to avoid sensitive foraging areas will help mitigate possible population impacts.
Expected impacts from wave energy developments on benthos are largely limited to the construction phase of development and relate to habitat disturbance, increased suspended sediment, sediment deposition, scour and abrasion and release of contaminants from dredged sediments. Potential operational impacts include changes in hydrodynamics and the introduction of new habitat types from foundation structures and/or other submerged equipment. The experience provided from test centres EIA suggests that the effects of the deployment of wave energy converters on coastal processes and geology would be insignificant in comparison to the natural processes occurring at the sites. Similarly, seabed disturbance from construction are generally considered to be local, temporary and similar in magnitude to common natural occurrences in the marine environment. Similarly, the evidence to date is that the potential impacts to fish and shellfish from wave energy developments are limited and of a short duration. The greatest potential for displacement effects is limited to construction phase and can be mitigated by keeping this phase as brief as possible. Entrapment and, to a lesser extent, collision remain as viable threats during the operation phase but can be mitigated by appropriate protective measures. Wave energy developments have credible potential to exhibit positive impacts, for example, by behaving similarly to fish attraction devices, artificial reefs and no take zones. At the Swedish Lysekil test centre, WECs were judged to exhibit clear features of artificial reefs (ARs), with expected positive effects.
A review of the EIAs performed at all of the test centres associated with SOWFIA confirms several lessons regarding the wave energy EIA process which were developed during SOWFIA. While the selection of receptors discussed in this report is confirmed by this experience, there is clear evidence that the receptors of primary interest are dependent on factors such as the local environmental characteristics, the presence/absence of protected species and the regulatory authority under which the EIA is performed. Across all test centres, the impacts which were perceived as lowest significance were air quality and climate and water quality and ground water with physical processes as the next least significant.
Some common themes appear in the study of EIA for wave energy projects. These include: the necessity of two years of monitoring to provide a baseline sufficient to detect changes attributable to the presence of WECs; the lack of any documented evidence of significant behavioural effect on a species level from EMF emissions by any existing undersea power cables; the logistical preference for BAG design on impact studies due to the BACI requirement for an appropriate independent control site and the high number of replicates required to achieve the desired level of impact detection sensitivity.
Finally, concern related to cumulative impacts from an expanding level of wave energy development taking place in a background of growing utilisation of the marine environment which is difficult for individual developers to address adequately suggest that this issue be comprehensively addressed at the national level as part of SEA.