Electrical power generation from wind farms has grown rapidly in the UK and European Union (EU) in the last decade and is set to grow further. By 2020, the EU proposes to source 20% of energy from renewable sources (Directive 2009/28/EC). Wind energy is expected to provide 9–14% of global electricity generation by 2050 (IPCC 2011). This may eventually reduce climatic change and its negative impacts on biodiversity, but there are also several poorly quantified negative effects on wild species of renewable energy generation, including wind turbines. For example, birds and bats are killed by colliding with turbine blades or towers and there may be effects of wind farms on mortality and reproductive rates of a wide range of species from avoidance and displacement. Birds may incur additional costs or forego benefits because of reduced transit or foraging within or near to wind farms (Drewitt & Langston 2006; Searle et al. 2014). Depending upon the strength of density-dependent compensatory processes, these effects could reduce the population to a lower stable level or cause its extinction (Wade 1998; Niel & Lebreton 2005). Except in the rare circumstances where density dependence is exactly compensating, such effects would always diminish population size. Positive effects of renewable energy infrastructure on populations of wild species have also been proposed and, in a few cases, quantified. These include possible enhancement of food resources of seabirds by protection from fishing from the presence of offshore installations and the provision of artificial substrates as habitat for fish and invertebrates (Inger et al. 2009; Langhamer, Wilhelmsson & Engström 2009).
The UK has the best wind resources in Europe (DECC 2011). Although the cost per megawatt-hour of electricity generation from offshore wind turbines averages about twice that for onshore installations (Bilgili, Yasar & Simsek 2011; Chu & Majumdar 2012), offshore wind power is currently favoured over onshore by the present UK government because of public perceptions of nuisance and landscape consequences of onshore turbines. The UK also has internationally important breeding populations of seabirds. It holds more than 10% of the world's breeding population of eight species, of which three have more than half of their global breeding population in the UK (Brown et al. 2015). Because seabirds range over long distances, there may be cumulative impacts on a breeding colony from several wind farms (Masden et al. 2010). Seabirds are long-lived and late-maturing, which renders their population growth rate particularly sensitive to additional mortality from collisions or displacement (Niel & Lebreton 2005). The importance of these seabird populations and their sensitivity places a heavy responsibility on those conducting and acting upon scientific assessments of the impacts of offshore wind farms on seabirds to comply with the protection measures and the precautionary principle enshrined in the EU Birds and Habitats Directives (Directive 2009/147/EC and Council Directive 92/43/EEC).
For the UK, and other countries within the European Union, the regulation of wind farm construction requires the assessment of possible damage to the integrity of sites and populations under the EU Habitats and Birds Directives. Consideration must be given to impacts on bird populations of a project on its own and in combination with others already in existence, given consent or planned. Governments give or refuse consent for the construction of wind farms after taking into account the scale and level of certainty of the impacts indicated by these assessments. However, there are no definitive quantitative thresholds or criteria defining how large or likely expected impacts must be for damage to the integrity of sites and populations to be anticipated and for consent for wind farm construction to be denied or limited. Consent can be granted only if it is ascertained that there will not be an adverse effect on the integrity of a Natura site, excepting in cases where there are imperative reasons of overriding public interest for consent and no alternative solutions (Article 6(4) of Directive 92/43/EEC). In recent years, several plans for large offshore wind farms have been approved and some built in UK and EU waters close to large seabird populations because the competent authority judged there was no expected adverse effect on the integrity of the Natura sites involved. For example, in 2014 approval was granted for several extensive wind farms at Hornsea (England, UK Government) and the Firth of Forth (Scotland, Scottish Government), close to internationally important breeding populations of seabirds. This approach contrasts with that in some other EU states. In Germany and Denmark, for example, offshore wind farms have been subject to rigorous marine spatial planning with the aim of avoiding potential conflict with nature conservation as part of the required Strategic Environmental Assessment (SEA) process recommended in EU Commission guidance (European Commission 2011). The German Cabinet approved Europe's first maritime spatial plan in September 2009, after a considerable effort in terms of surveys and research to identify marine sites of high nature value and potential conflict areas with wind farms and to establish zones for various activities and infrastructure. The offshore SEA covering UK waters is not of comparable quality.
In this perspective, we argue that the methods and data used in these cases for estimating effects upon seabird demographic rates and translating them into potential impacts on seabird populations do not allow adequate assessment of effects on site integrity. As a result, sound science and its logical interpretation are lacking in Environmental Impact Assessments of this large and expanding industry.