The UK government has a target for sourcing 15% of energy from renewable sources by 2020. A significant component of this is likely to be produced by wave and tidal stream energy convertors. At present a total of over 30 such projects in UK waters are under operation, testing or development, and large scale investment is being made into the development of suitable technology. Once the technology is developed there will be an influx of applications for the installation and operation of arrays of wave and tidal stream devices, but these will have as yet undetermined impacts on the marine environment. An important component of this environment is seabirds and the UK hosts a seabird assemblage of outstanding international importance. This review is a response to the lack of knowledge on how these emerging technologies will impact on this assemblage, as well as some other potentially affected species, and it aims to use an ecological approach to understand the potential nature of these impacts. Currently, there is very limited experience of operational wave and tidal stream devices at sea, and hence very little information about their impacts on marine birds. It is therefore necessary to only make inferences about potential impacts from a theoretical background, based on review of current technological and ecological knowledge.
Marine birds can be potentially affected by wave and tidal stream developments in a number of ways. These may be direct or indirect, adverse or beneficial, temporary or long term. In the majority of cases, little or nothing is known about the likelihood of occurrence or the scale of such an impact. Impacts are likely at three distinct stages in the life of a development, installation, operation and decommissioning, and in this review installation and decommissioning are considered together. During installation and decommissioning, the threats to seabirds will be from collision, disturbance, habitat exclusion and displacement, changes to sedimentary processes, and pollution. These threats will also apply during operation, in addition to potential habitat creation and a possible increase in predation.
While the risks to seabirds from wave and tidal steam devices are largely undefined, this review takes the approach of examining the component parts of such devices and to drawing structural parallels with existing human activities. Such component parts are vessels, sea bed structures, mooring equipment, surface structures, turbines, traps and attractants, either lights or fish aggregating devices. In addition ecological aspects of the receptors, marine birds, are also examined. These are physiology, that is visual and aural sensitivity; geography, breeding, wintering, foraging, rafting and moulting areas, including protected areas; demography, potentially affected birds in the context of their biogeographical population; and foraging ecology, mode and rhythm.
Existing wave and tidal stream devices are described, in generic terms, to reflect the fact that the technology is evolving rapidly, and detailed descriptions of individual devices are likely to be superseded. However, an appendix lists those devices that are currently operational or in development. The review then details the suite of UK marine bird species that will potentially be affected and describes the ecological characteristics of each, in terms of conservation status, distribution, ecology and vulnerability. This section of the review also contains coastal waders, raptors and chough that could be potentially affected, notably by disturbance.
For any development, ornithological surveys will be required, and these surveys will then be used to determine potential receptors and impacts. These surveys should not just be of the immediate development area, but should also provide ecological context, and so the methods used for survey must be carefully considered. As seabird distribution is stochastic, densities and behaviours are highly variable and therefore need to be surveyed with a high spatial and temporal resolution. Understanding the mechanisms of this natural variability is vital for any assessment of whether a development has caused change in bird behaviour or distribution. Therefore, distribution patterns need to be described in the context of a variety of biotic and abiotic factors and coverage must include as broad a variety of conditions as logistically and safely possible. Surveys may include components of desk study, boat survey, aerial survey and remote sensing.
In this review we have noted that there is a paucity of applicable data on the impacts of wave and tidal devices on birds. This lack of data has implications for understanding the overall impacts of these novel technologies, and for impact assessment of individual schemes. In the final section these knowledge gaps and approaches to filling them are discussed. The key information that is lacking can be summarised as spatial and behavioural. We identify the practical issues for data collection: a need for standardisation throughout the industry, the use and development of remote sensing, further refinement of modelling techniques; refining sensitivity indices, defining the scale of impacts, and cumulative impact assessment.