Editor’s Choice - Towards understanding the population-level effects of wind farms on birds
April 2012 (Issue 49:2)
Pearce-Higgins, J. W., Stephen, L., Douse, A. & Langston, R. H. W. (2012) Greater impacts of wind farms on bird populations during construction than subsequent operation: results of a multi-site and multi-species analysis. Journal of Applied Ecology, 49, 386-394.
|Photo credit: Derek Belsey|
In an effort to combat climate change by reducing CO2 emissions, governments worldwide have set ambitious targets for renewable energy generation. As a result, the wind energy sector has grown rapidly in recent years, with over 3000 wind turbines now installed in 300 wind farms in the UK alone (RenewableUK 2012).
Despite their vital contribution to green energy generation, there is evidence that wind turbines can have adverse impacts on wildlife. For example, turbines can cause direct mortality in birds or bats due to collisions with turbine rotors or towers. While certainly substantial in some sites (e.g. Smallwood & Karas 2009), estimates of such mortality vary widely (Drewitt & Langston 2006; Rydell et al. 2010). In addition, the presence and/or operation of wind turbines can cause displacement or disturbance effects. For example, densities of breeding or foraging birds can be lower nearer turbines (e.g. Larsen & Madsen 2000; Pearce-Higgins et al. 2009) or flight routes may be affected (e.g. Larsen & Guillemette 2007) leading to effective habitat loss. In spite of efforts to document such effects of wind farms at a variety of sites, their consequences for the population dynamics of affected species remains unclear. A better understanding of population-level impacts of wind turbines is crucial to allow environmental planners and policy makers to make decisions that successfully balance contributions to renewable energy targets with effective nature conservation.
|Photo credit: Derek Belsey|
It is precisely this research need that is addressed by Pearce-Higgins et al. in this issue’s Editor’s Choice. Using long-term monitoring data of a range of upland bird species at 18 wind farm sites in the UK, they compare breeding bird densities and population trends between years before, during and after wind farm construction. Moreover, they contrast these effects at wind farms with paired reference sites acting as controls. Using this method, they are able to show that in line with previous work (Barrios & Rodriguez 2004; Pearce-Higgins et al. 2009) the effects of wind farms on bird densities vary considerably among species. Of the 10 species they analyse data for, the densities of snipe Gallinago gallinago (L.), curlew Numenius arquata (L.) and red grouse Lagopus lagopus scoticus (Lath.), are lower during construction compared to pre-construction. While the densities of the latter appeared to recover during the first years of wind farm operation, the densities of both snipe and curlew remained depressed. Further support for the specific effect of wind farm construction as opposed to operation comes from two additional findings. First, curlew densities were also significantly lower during construction on wind farm sites, when compared to densities on paired control sites. Second, in spite of adverse effects on densities of some species during wind farm construction, the authors find little evidence for longer-term population declines in the years thereafter.
The results presented in this study are particularly significant for a number of reasons. First of all, the authors explicitly separate the effects of wind farm construction from that of its subsequent operation. Even though the potential for disturbance effects during construction has been recognized previously (Drewitt & Langston 2006) and statutory monitoring often takes place throughout planning, construction and development phases of wind farm developments, very few studies explicitly investigate adverse effect due to construction per se. As Pearce-Higgins et al. suggest, short-term effects on breeding densities during construction, combined with a lack of longer-term effects on population dynamics, suggests at least some species may habituate to the presence of turbines after the disturbance associated with wind farm construction has passed. Very few studies have lasted for long enough to test for such effects (Madsen & Boertmann 2008), further stressing the need for more longer-term monitoring at wind farm sites (Stewart, Pullin, & Coles 2007).
Second, the authors combine monitoring data from 18 sites. Such multi-site comparisons remain very rare, in spite of extensive evidence to show that the effects of wind farms on wildlife can vary substantially among sites (e.g. Stewart, Pullin, & Coles 2007). This may be in part because multi-site studies are logistically challenging. Moreover, much of the monitoring at wind farm sites is done by commercial consultancies that are often bound by confidentiality agreements, making the sharing or even publishing of (at least some) data problematic. Regardless of such issues, the present study demonstrates why it is vital to compare the effects of wind farms across sites if we are to fully understand their effects on wildlife generally.
Finally, in a previous issue’s Editor’s Choice four years ago (Elphick 2008), the need for studies which demonstrate possible population-level impacts of wind turbines on birds was highlighted. More recently, there have been increased calls from the consultancy sector for more studies of the effects of developments on important species (e.g. those of conservation concern), in particular at a population level (Hill & Arnold 2012). The work presented here by Pearce-Higgins et al. does exactly this in the context of wind farm developments, making an excellent case for further study, especially longer-term demographic studies of birds at a range of wind farm sites. Increasingly, such studies will involve collaborations between a range of stakeholders - wind farm developers, ecological consultants, NGO’s and academics. As such, this study is an excellent example of how high quality applied research produces substantial real-world impact (Milner‐Gulland et al. 2012).
Barrios, L. & Rodriguez, A. (2004) Behavioural and environmental correlates of soaring-bird mortality at on-shore wind turbines. Journal of Applied Ecology, 41, 72–81.
Drewitt, A. & Langston, R. (2006) Assessing the impacts of wind farms on birds. Ibis, 148, 29–42.
Elphick, C. (2008) Editor’s choice: New research on wind farms. Journal of Applied Ecology, 45, 1840–1840.
Hill, D. & Arnold, R. (2012) Building the evidence base for ecological impact assessment and mitigation. Journal of Applied Ecology, 49, 6–9.
Larsen, J. & Guillemette, M. (2007) Effects of wind turbines on flight behaviour of wintering common eiders: implications for habitat use and collision risk. Journal of Applied Ecology, 44, 516–522.
Larsen, J. & Madsen, J. (2000) Effects of wind turbines and other physical elements on field utilization by pink-footed geese (Anser brachyrhynchus): A landscape perspective. Landscape Ecology, 15, 755–764.
Madsen, J. & Boertmann, D. (2008) Animal behavioral adaptation to changing landscapes: spring-staging geese habituate to wind farms. Landscape Ecology, 23, 1007–1011.
Milner‐Gulland, E.J., Barlow, J., Cadotte, M.W., Hulme, P.E., Kerby, G. & Whittingham, M.J. (2012) Ensuring applied ecology has impact. Journal of Applied Ecology, 49, 1–5.
Pearce-Higgins, J.W., Stephen, L., Langston, R.H.W., Bainbridge, I.P. & Bullman, R. (2009) The distribution of breeding birds around upland wind farms. Journal of Applied Ecology, 46, 1323–1331.
RenewableUK. (2012). UKWED Statistics. Available at: http://www.bwea.com/statistics/. Accessed 08/03/2012.
Rydell, J., Bach, L., Dubourg-Savage, M., Green, M., Rodrigues, L. & Hedenstrom, A. (2010) Bat mortality at wind turbines in northwestern Europe. Acta Chiropterologica, 12, 261–274.
Smallwood, K. & Karas, B. (2009) Avian and Bat Fatality Rates at Old-Generation and Repowered Wind Turbines in California. Journal of Wildlife Management, 73, 1062–1071.
Stewart, G.B., Pullin, A.S. & Coles, C.F. (2007) Poor Evidence-Base for Assessment of Windfarm Impacts on Birds. Environmental Conservation, 34, 1–11.
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