In the first post of its kind for The Applied Ecologist’s blog, Dr Lucy Wright, RSPB Principal Conservation Scientist, discusses five articles published in the latest issue of Journal of Applied Ecology, which have been grouped into a special profile on wildlife and renewable energy. All five papers are currently free to read online.
Renewable energy is widely accepted to be a vital part of efforts to minimise climate change. Like all man-made developments, renewable energy installations alter their environment and poorly sited structures can have significant negative consequences for wildlife. Our job as applied ecologists is to understand how, why, where and when renewable energy developments have these consequences, in order to help decision makers site projects in the least damaging places, balancing the needs of climate change mitigation and nature conservation.
This issue features five papers addressing the interactions between wildlife and renewable energy structures.
Lack of sound science in assessing wind farm impacts on seabirds
The lack of direct measurements of the impacts of offshore wind turbines on seabirds is highlighted in the Practitioner’s Perspective by Rhys Green and colleagues. Scientists have developed models to predict seabird collisions with turbines, and the long-term consequences of this for their populations. Such models ought to go through an iterative process of testing (in a range of real-world situations) and refinement in order to produce robust predictions, but this has not happened; there is almost no published evidence measuring collisions or population-level impacts at offshore wind farms, so we cannot test whether the model predictions are accurate. Birds that do not collide might be affected in other ways; some species avoid the turbines but this can lead to the effective loss of important feeding sites, or increase energetic costs for seabirds commuting between nesting colonies and offshore feeding areas if flying around a wind farm adds distance to these regular journeys. These effects are even less well-studied at existing wind farms, and therefore even more poorly considered in impact assessments for new developments. Finally, the authors criticise the application of thresholds of “acceptable” levels of predicted impact to seabird populations at internationally important sites where birds are supposed to be protected. They argue that these thresholds have no biological basis and set out an alternative method for assessing impacts by comparing the predicted future population size with and without the wind farm. It is the job of policymakers to determine whether predicted impacts can be accepted and compensated for within current regulatory frameworks.
In light of the lack of evidence of impacts of offshore wind farms on seabirds, it is encouraging that two of the other papers in this series directly measure the impact of renewable developments on wildlife, while the other two quantify the behaviour of seabirds in the marine environment to help understand the likely vulnerability of particular species to particular types of renewable developments.
Measuring impact directly
Seals avoid wind farms only during pile driving
Offshore wind farm foundations are usually installed on the seabed by impact pile driving, effectively giant hammers that produce intense underwater sound pulses with each blow. Scientists are concerned that marine animals that are sensitive to underwater noise, such as seals, might leave important feeding areas as a result. However, this has not previously been measured because of the difficulty of observing animals that spend much of their time underwater. Debbie Russell and colleagues solved this problem by modifying mobile phones to create GPS tracking devices that were attached to harbour seals. This novel technology allowed comparison of seals’ movements during the construction of one wind farm and the operation of another with those measured before either wind farm was constructed. The work demonstrates that seals avoided the area within 25 km of wind farm construction only during the discrete periods when pile driving was carried out – their distribution returned to normal within 2 hours after pile driving stopped, and appeared unaffected by other construction activities or wind farm operation.
Raptors take different flight paths to avoid wind farms
Wind farms on land can be risky for migrating raptors and previous studies have demonstrated that collisions may occur if turbines are built on important migration routes, while it has been theorised that long rows of turbines might cause birds to alter their migration routes, potentially increasing their energetic costs. Sergio Cabrera-Cruz and Rafael Villegas-Patraca studied the response of raptors to a 7.5 km long row of wind turbines on an important migratory corridor in southern Mexico. Combining visual observations of millions of birds over several years, and radar to measure their flight trajectories, they demonstrate that raptors took different flight paths after the wind farm was constructed compared to before, thereby avoiding the turbines. This is in contrast to the findings of other studies that have suggested that raptors at some other wind farm sites do not avoid turbines, and demonstrates the importance of understanding the site- and species-specific features that may influence how animals respond to new developments.
Improving predictions of impacts
Quantifying where seabirds coincide with areas suitable for tidal stream turbines
Tidal stream turbines are installed underwater to capture energy from strong currents. There are plans to increase the use of these devices in the near future, with uncertain impacts on local wildlife. James Waggitt and colleagues measured how pursuit-diving seabirds (such as puffins, guillemots and shags) used fine-scale physical features (e.g. different types of current, seabed and water turbulence) in Orkney where tidal stream turbines are being tested. They identified where the areas used by seabirds coincide with areas suitable for turbine deployment. Puffins were most likely to be affected by turbines since they were normally found in places with the high horizontal currents necessary for turbines to work efficiently; other seabirds also used these areas. Several species were associated with downward vertical currents (which sometimes coincide with the strong horizontal currents necessary for turbines) and the authors suggest that to minimise the impact on seabirds, turbine installations should focus on locations with strong horizontal currents that do not also have downward vertical currents. Further work will be required to understand whether and how turbine installations actually affect the species thought to be at risk. It is unfortunate that a confidentiality agreement prevented the authors from accessing information about where turbines were operational at the test site during the study, as this would have allowed some preliminary measurement of how seabirds respond to these novel devices.
Modelling seabird flight heights to predict collision risk
The final paper in this series revisits seabird collision risk with offshore wind turbines. Flight height is critical in predicting collision risk since only birds flying at the height of turbine rotors are at risk of colliding with them. Conventional flight height estimates come from boat or aerial surveys conducted in daylight and good weather conditions, and so collision risk models must make assumptions about birds’ behaviour at other times. Viola Ross-Smith and colleagues tackle this data gap using a Bayesian approach to analyse height data from GPS tracking devices on two seabird species. Great skua flight height was relatively consistent between day and night, but lesser black-backed gulls flew lower at night than during the day, making them more likely to fly underneath the turbine rotors at night. The modelling approach used here could be applied to other tracking data sets to improve our understanding of animal movements in other situations.
Learning from existing renewable energy installations for a better future
Together, these studies reveal the advances being made in our understanding of how some types of renewable energy installations affect some types of wild animals, with new technologies contributing to the measurement of impacts of onshore wind farms on raptors, offshore wind farms on seals and our grasp of how seabird behaviour might affect their exposure to offshore turbines both below and above the water. However, they also expose the many questions we still need to answer to fully understand the effect of these developments on wildlife, often due to a lack of appropriate research at existing sites. We must invest in sound science if we are to understand how best to manage two of the most pressing issues affecting our natural world – climate change mitigation and nature conservation.
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