Renewable energy technologies are commonly seen as a panacea for the environmental problems associated with power generation, not just in terms of greenhouse gas emissions but also by virtue of other impacts such as pollution and habitat destruction (e.g. Dincer 1999). This may well be true of wave and tidal energy developments, but the fact is that there are few direct observations from which to judge the nature and scale of impacts. This is partly because of the emergent state of the industry, but also because research into this field has tended to focus on the nature of the resource and on the engineering aspects of exploiting it rather than on the environmental consequences of such exploitation.
This is not to say that there is no evidence base from which to draw inferences on the potential for wave and tidal energy developments to impact upon the marine environment. Information from impact studies of other human activities provide valuable insights into how some aspects of power generation may interact with the environment. Coupled with knowledge about the vulnerabilities of particular species and habitats and about the interrelatedness of physical and ecological processes, this information provides at least a starting point for understanding the likely consequences of marine energy extraction for the physical and biological milieus in which it is placed. A number of recent reviews (e.g. Gill 2005, Inger et al. 2009, ICES 2010a, 2010b, Shields et al. 2011) have drawn together much relevant information for a qualitative appreciation of the perceived potential for environmental interactions involving marine renewable energy developments. Several types of interaction may be distinguished:
- energy extraction impinging upon natural processes
- operational effects on marine biota, acting through device operation, maintenance and decommissioning
- provision of new ecological space through the physical presence of devices and other development structures
- displacement of other human activities, modifying the locus and nature of their impacts
The least attention has so far been paid to the first of these aspects, particularly in terms of intervention in physical processes. For this reason, this document places particular emphasis on the previously under-reviewed topic of potential impacts on physical processes, the more so because many other potential impacts stem from the physical impacts as first causes. We pull together the first comprehensive review of the potential for wave and tidal energy extraction to impinge upon physical processes in the near- and far-fields of developments, before going on briefly to examine the implications for ecological processes. Operational effects are considered mainly in terms of noise and collision risk; pollution risk involving release of oil and chemicals is probably fairly low, and is a general risk for human activities at sea rather than being particular to wave and tidal energy extraction. Changes to ecological space are considered in terms of reef effects and structures functioning as fish aggregation devices. Finally, we focus on marine fishing as the principal interaction with other sea users that is likely to have environmental implications.