The temperate west coast of Scotland, from Burrow Head, Galloway to Unst, Shetland, hosts several areas that may be suited for the placement of devices designed to extract the energy contained in wind-induced waves or tidally induced currents. These areas are, by their very nature, exposed to waves or strong tidal currents and support quite different biological communities.
Within the region under review, the wave-exposed shorelines are characteristically steep, rocky and backed by cliffs. Such exposed shorelines are typically poor in terms of species diversity, a trend that continues subtidally where sediments are coarse and mobile. Conversely rocky areas that are exposed to rapid tidal currents, without the extreme rigour of an open oceanic aspect, typically host high biodiversity, unique biological assemblages and are relatively scarce. As a consequence tidal rapids are a priority habitat under the UK Biodiversity Action Plan.
Wave-and tide-powered devices will be located in quite different receiving environments and therefore have quite different impacts on the local benthos. Wave generators are likely to have minimal impact as they are not likely to significantly reduce the wave energy reaching the shoreline behind them. The moorings of such structures may have very localized impacts that will be commensurate with the degree of change in the nature of the sediment caused. With careful siting it is doubtful if associated changes in the benthos would be considered deleterious. Tide-powered devices are more likely to be located in areas with high benthic conservation value. Structures that reduce the mean velocity of water moving through a restricted tidal channel are likely to cause a shift in community structure commensurate to the decrease in current speed. Where a significant reduction occurs the resultant re-structuring of the community, to one associated with a decreased current flow, might be considered deleterious.
Within the reviewed area there are several sites considered of particular conservation value. These include the Firth of Lorn, Sound of Barra, and Kyle Rhea area.
In order to make a proper assessment of the likely benthic impact of power-generation devices, and advise regarding the siting of various components, the receiving environment needs to be extensively mapped using a suite of acoustic and visual methods. Of the areas reviewed here only the Firth of Lorn and Sound of Barra have been adequately covered in this way.
Acknowledgement: This article was identified by the Crown Estate Wave and Tidal Knowledge Network.