As a means of reducing dependence on fossil fuels and thereby combating global climate change, tidal power offers a potentially valuable renewable energy source. The UK coastline has some of the highest tidal ranges in the world and proposals for tidal power schemes have thus been put forward for several estuaries where the tidal range is sufficiently large for energy to be harnessed, including the Severn, Mersey, Dee and Solway.
Although the energy supply at such sites is reliable and plentiful, the development of any tidal power scheme would have great implications for the ornithological interest of the site in question. The UK holds a significant proportion of Europe’s estuarine resource and its estuaries and other wetlands are of considerable international importance for migrant and wintering waterbirds. A peak of 2 907 731 waterbirds, for example, was counted by the Wetland Bird Survey (WeBS) in the UK in winter 2008/09 (Calbrade et al. 2010). Many of these wetland sites are designated as Special Protection Areas (SPAs; under the EC ‘Birds Directive’ 2009/147/EC) as part of the Natura 2000 network, or as Wetlands of International Importance under the Ramsar Convention.
Here we describe the key issues that need to be evaluated as part of any assessment of the effects of a tidal power scheme on birds, as considered in the recent Strategic Environmental Assessment (SEA) undertaken as part of the Severn Tidal Power Feasibility Study. The Severn Estuary is designated as both an SPA – with 18 spring/autumn passage or over-wintering waterbird species listed as features – and a Ramsar site, and encompasses seven Sites of Special Scientific Interest (Burton et al. 2010). A mean annual peak of 72 909 waterbirds was recorded there by WeBS counts over the period 2004/05–2008/09 (Calbrade et al. 2010). Five different tidal power options – three barrage schemes and two lagoon schemes – have been considered by the feasibility study and SEA (Fig. 1)