Cumulative Impact Management: Cumulative Effects Case Studies
Birds and wind farms: Assessing cumulative impacts
1
With the rapid growth of the wind power industry in recent years to meet EU renewable energy targets, there are environmental concerns over increasing numbers of wind farms and the potential negative impact on wildlife populations, particularly birds. Potential impacts on birds can be categorised into three types: direct mortality due to collision with turbines; physical habitat loss due to the footprint of the turbines; and displacement due to behavioural responses of birds to the turbines (Fielding et al. 2006; Fox et al. 2006). The latter includes extension of flights, where wind farms act as barriers to movement. Here we develop an approach to evaluate the impact, in terms of barrier effects, associated with wind farms, using the example of common eider (Somateria mollissima) interacting with an offshore wind farm. Introduction Study site and species The study site covered the Nysted offshore wind farm, south of Denmark (Figure 1). Flight trajectories of eiders were collected using surveillance radar (Desholm and Kahlert 2005). Between 200 000 and 300 000 migrating eiders pass the study site each spring and autumn (Petersen et al. 2006). Data analyses Deviation from a straight-line trajectory (curvature) was estimated to assess the additional distance travelled by eiders in the presence of the wind farm. Trajectories were grouped into those recorded pre- and post-construction, and then categorised further as near or far from the wind farm. We estimated the additional distance travelled by eiders post-construction: Distance = (Curvaturepost - Curvaturepre) * Median trajectory length The associated energetic cost was estimated using Flight 1.18 (Pennycuick 2007) and then compared to the overall energetic cost of migration. We investigated the energetic costs of eiders avoiding additional wind farms, based on multiples of the response observed at Nysted (Masden et al. 2009). Barriers to movement Birds show varying avoidance responses to wind farms (Hötker et al. 2006). Comparison of the pre- and post-construction data from Nysted showed that eiders avoided the wind farm (Figures 2 & 3). The extra distance travelled due to this avoidance response was ~ 500 metres; a likely trivial addition for eiders migrating < 1400km. The energetic cost of avoidance and increased distance travelled could reduce the mass and condition of an individual thus adversely affecting breeding success. However, the energetic cost associated with eiders avoiding the Nysted wind farm was undetectable and required a response equivalent to passing 100 similar wind farms to achieve a loss in body mass in excess of 1% (Table 1). Therefore, the cost of avoiding one wind farm during a migration event is insignificant compared with factors such as strong or unfavourable wind conditions. Impact on migrating birds Birds and wind farms: Assessing cumulative impacts Elizabeth Masden 1 , Dan Haydon 1 , Tony Fox 3 , Bob Furness 1 , Rhys Bullman 2 and Mark Desholm 3 1 Division of Ecology & Evolutionary Biology, University of Glasgow; 2 Scottish Natural Heritage, Great Glen House, Inverness; 3 NERI, Department of Wildlife Ecology & Biodiversity, Denmark This study was based on several assumptions that should be tested. 1. We only considered birds interacting with the wind farm during an annual migration event. For an individual commuting many times a day between a breeding colony and foraging areas, the cost may be very different. Therefore, we are extending this work on eiders and assessing the cost for a suite of breeding seabird species. 2. We only considered the specific configuration of the Nysted wind farm. Birds approaching wind farms from different angles may react differently, as the wind farm may be perceived more or less, as a barrier. We are developing a movement model to test the effect of different configurations of turbines. Future projects Using a novel approach, we assess the impact and energetic costs of avoidance behaviour associated with an offshore wind farm. We conclude that for a long-distance migratory seaduck such as the common eider, the impact is small and likely trivial. Conclusions Figure 1: Estimated migration route of eiders and corresponding straight-line distance. Capture sites of breeding (triangles) and wintering (dots) eiders. Insert denotes study site and example tracks. Nysted Wind Farm Factor Distance Travelled (km) Cost (kJ) Fat burnt (kJ) Mass (kg) 0 1200 13300 12700 2.06 0 1400 15200 14400 2.00 2 1401 15200 14400 2.00 4 1402 15200 14400 2.00 10 1405 15200 14400 2.00 100 1450 15600 14800 1.98 1000 1900 19500 18500 1.85 3000 2900 26900 25600 1.61 4000 3400 30200 28700 1.50 Christensen, T.K. 2008 Factors affecting population size of Baltic Common Eiders. University of Copenhagen. Desholm, M.; Kahlert, J. 2005 Avian collision risk at an offshore wind farm. Biology Letters. 1: 296-298 Fielding et al. 2006 Spatial association as an indicator of the potential for future interactions between wind energy developments and golden eagles Aquila chrysaetos in Scotland. Biol Conserv. 131: 359-369 Fox et al. 2006 Information needs to support environmental impact assessment of the effects of European offshore wind farms on birds. Ibis. 148: 129-144 Hötker et al. 2006 Impacts on biodiversity of exploitation of renewable energy resources: the example of birds and bats. Michael-Otto-Institut im NABU, Bergenhusen. Masden et al. 2009 Barriers to movement: impacts of wind farms on migrating birds. ICES J Mar Sci Pennycuick, C.J. 2007 Flight 1.18 for Windows. http://www.bio.bristol.ac.uk/people/pennycuick.htm . Petersen et al. 2006 Final results of bird studies at the offshore wind farms at Nysted & Horns Reef, Denmark: NERI References Figure 3 (left): Curvature of eider tracks Kruskal-Wallis: χ 2 = 89.8, d.f. = 3, p < 0.05. Letters denote significant differences; multiple comparisons test, α= 0.05. Table 1 (above): Estimated cost of flight associated with increasing distance travelled as a consequence of an avoidance response. Pre-Near Pre-Far Post-Near Post-Far Category 1.00 1.05 1.10 1.15 1.20 Curvature a a b a Figure 2: Kernels of space use by eiders across the study area (a) pre-construction & (b) post-construction of the Nysted wind farm. Darker colour represents greater use. Black dots denote wind turbine locations. Grey dot denotes the radar observation tower. a b Many thanks to the Finnish Ringing Centre for providing information on breeding and wintering eider, and Thomas Kjær Christensen and Henning Noer for advice on eider breeding biology. Thanks also to Hawthorne Beyer & Ib Krag Petersen for advice on spatial analysis. EAM was funded by an SNH studentship. Acknowledgements
Transcript of Birds and wind farms: Assessing cumulative impacts
With the rapid growth of the wind power industry in recent years to meet EU renewable energy targets, there are environmental concerns over increasing numbers of wind farms and the potential negative impact on wildlife populations, particularly birds.
Potential impacts on birds can be categorised into three types: direct mortality due to collision with turbines; physical habitat loss due to the footprint of the turbines; and displacement due to behavioural responses of birds to the turbines (Fielding et al. 2006; Fox et al. 2006). The latter includes extension of flights, where wind farms act as barriers to movement.
Here we develop an approach to evaluate the impact, in terms of barrier effects, associated with wind farms, using the example of common eider (Somateriamollissima) interacting with an offshore wind farm.
Introduction
Study site and speciesThe study site covered the Nysted offshore wind farm, south of Denmark (Figure 1). Flight trajectories of eiders were collected using surveillance radar (Desholm and Kahlert 2005). Between 200 000 and 300 000 migrating eiders pass the study site each spring and autumn (Petersen et al. 2006).
Data analysesDeviation from a straight-line trajectory (curvature) was estimated to assess the additional distance travelled by eiders in the presence of the wind farm. Trajectories were grouped into those recorded pre- and post-construction, and then categorised further as near or far from the wind farm. We estimated the additional distance travelled by eiders post-construction:
Distance = (Curvaturepost - Curvaturepre) * Median trajectory length
The associated energetic cost was estimated using Flight 1.18 (Pennycuick 2007) and then compared to the overall energetic cost of migration. We investigated the energetic costs of eiders avoiding additional wind farms, based on multiples of the response observed at Nysted (Masden et al. 2009).
Barriers to movement
Birds show varying avoidance responses to wind farms (Hötker et al. 2006). Comparison of the pre- and post-construction data from Nysted showed that eiders avoided the wind farm (Figures 2 & 3). The extra distance travelled due to this avoidance response was ~ 500 metres; a likely trivial addition for eiders migrating < 1400km.
The energetic cost of avoidance and increased distance travelled could reduce the mass and condition of an individual thus adversely affecting breeding success. However, the energetic cost associated with eiders avoiding the Nysted wind farm was undetectable and required a response equivalent to passing 100 similar wind farms to achieve a loss in body mass in excess of 1% (Table 1). Therefore, the cost of avoiding one wind farm during a migration event is insignificant compared with factors such as strong or unfavourable wind conditions.
Impact on migrating birds
Birds and wind farms: Assessing cumulative impacts
Elizabeth Masden1, Dan Haydon1, Tony Fox3, Bob Furness1, Rhys Bullman2 and Mark Desholm3
1 Division of Ecology & Evolutionary Biology, University of Glasgow; 2 Scottish Natural Heritage, Great Glen House, Inverness; 3 NERI, Department of Wildlife Ecology & Biodiversity, Denmark
This study was based on several assumptions that should be tested. 1. We only considered birds interacting with the wind farm during an annual migration
event. For an individual commuting many times a day between a breeding colony and foraging areas, the cost may be very different. Therefore, we are extending this work on eiders and assessing the cost for a suite of breeding seabird species.
2. We only considered the specific configuration of the Nysted wind farm. Birds approaching wind farms from different angles may react differently, as the wind farm may be perceived more or less, as a barrier. We are developing a movement model to test the effect of different configurations of turbines.
Future projects
Using a novel approach, we assess the impact and energetic costs of avoidance behaviour associated with an offshore wind farm. We conclude that for a long-distance migratory seaduck such as the common eider, the impact is small and likely trivial.
Conclusions
Figure 1: Estimated migration route of eiders and corresponding straight-line distance. Capture sites of breeding (triangles) and wintering (dots) eiders. Insert denotes study site and example tracks.
Nysted Wind Farm Factor
Distance Travelled (km)
Cost (kJ)
Fat burnt (kJ) Mass (kg)
0 1200 13300 12700 2.06 0 1400 15200 14400 2.00 2 1401 15200 14400 2.00 4 1402 15200 14400 2.00 10 1405 15200 14400 2.00 100 1450 15600 14800 1.98 1000 1900 19500 18500 1.85 3000 2900 26900 25600 1.61 4000 3400 30200 28700 1.50
Christensen, T.K. 2008 Factors affecting population size of Baltic Common Eiders. University of Copenhagen.Desholm, M.; Kahlert, J. 2005 Avian collision risk at an offshore wind farm. Biology Letters. 1: 296-298Fielding et al. 2006 Spatial association as an indicator of the potential for future interactions between wind energy developments and golden eagles Aquila chrysaetos in Scotland. Biol Conserv. 131: 359-369Fox et al. 2006 Information needs to support environmental impact assessment of the effects of European offshore wind farms on birds. Ibis. 148: 129-144Hötker et al. 2006 Impacts on biodiversity of exploitation of renewable energy resources: the example of birds and bats. Michael-Otto-Institut im NABU, Bergenhusen. Masden et al. 2009 Barriers to movement: impacts of wind farms on migrating birds. ICES J Mar SciPennycuick, C.J. 2007 Flight 1.18 for Windows. http://www.bio.bristol.ac.uk/people/pennycuick.htm. Petersen et al. 2006 Final results of bird studies at the offshore wind farms at Nysted & Horns Reef, Denmark: NERI
References
Figure 3 (left): Curvature of eider tracks Kruskal-Wallis: χ2 = 89.8, d.f. = 3, p < 0.05. Letters denote significant differences; multiple comparisons test, α= 0.05. Table 1 (above): Estimated cost of flight associated with increasing distance travelled as a consequence of an avoidance response.
Pre-Near Pre-Far Post-Near Post-FarCategory
1.00
1.05
1.10
1.15
1.20
Cur
vatu
re
a
a
b
a
Figure 2: Kernels of space use by eiders across the study area (a) pre-construction &(b) post-construction of the Nysted wind farm. Darker colour represents greater use. Black dots denote wind turbine locations. Grey dot denotes the radar observation tower.
a
b
Many thanks to the Finnish Ringing Centre for providing information on breeding and wintering eider, and Thomas Kjær Christensen and Henning Noer for advice on eider breeding biology. Thanks also to Hawthorne Beyer & Ib Krag Petersen for advice on spatial analysis. EAM was funded by an SNH studentship.
Acknowledgements
