How to study the effects of offshore wind energy on birds and bats in the Eastern United States

Background

With a goal of 45 gigawatts of installed offshore wind capacity increasing in the United States by 2035, the potential exists for increasing impacts on birds and bats. Currently, there is a lack of a consistent methodology to study offshore wind's impacts on birds and bats, which limits the comparability of findings among studies. The three main potential impacts on birds and bats that warrant study are

• Collision mortality: primarily driven by how much avoidance occurs
• Behavioral responses (displacement, attraction): birds/bats change their foraging roosting or breeding habitat use in response to the presence of turbines
• Habitat effects that change prey abundance and availability (reef effects, substrate disturbance)

Research led by the Biodiversity Research Institute and collaborators developed a list of research priorities to better understand the effects of offshore wind on birds and bats and provide study design recommendations. This framework and recommendations will provide insights into offshore wind's impacts and facilitate the NEPA process, which is required for permitting a successful offshore wind project.

Study Design

The Biodiversity Research Institute and collaborators developed this research framework during a New York State Environmental Technical Working Group workshop with a diverse range of scientists, representatives of non-governmental organizations, and developers. Workshop attendees participated in discussions and breakout groups with specific focus areas and were tasked with developing research priorities for their focus areas. Outputs from the breakout groups were consolidated and formed the basis of the research priorities defined in this study.

Research focus areas

Exposure

Exposure occurs when animals overlap in space and time with offshore wind turbines. Only animals exposed to offshore wind structures can be affected through collisions and behavioral or habitat-mediated effects. Therefore, understanding how and when exposure occurs can improve our knowledge of wind-wildlife impacts. The primary exposure-related research questions involve a better understanding of

• Factors that influence exposure to turbines for different species
• How prey distribution influences the distribution of pelagic birds
• The effectiveness of species distribution models for predicting exposure
• Comparing bat exposure offshore to onshore and what factors influence these differences

Collision effects

Collisions occur when wildlife contact the blades or monopole and get killed or injured. Understanding the behavioral and environmental factors that influence collisions is critical for implementing strategies to reduce them. The important collision research questions should focus on

• Frequency of collisions relative to how often wildlife is exposed
• Factors that influence vulnerability to collisions
• Rates of mesoscale and microscale avoidance
• Influences of offshore wind infrastructure on bat species composition and activity
• Relationships of preconstruction exposure and collision risk
• Accuracy of collision risk models for birds

Behavioral effects

Offshore wind affects bird and bat behavior through displacement, avoidance, and attraction. Displacement occurs when wildlife changes their habitat due to the presence of structures, causing habitat loss. Avoidance occurs when an individual attempts to avoid a collision at the wind farm, wind turbine, or blade level. Attraction occurs when wildlife are drawn to a structure with the potential perching or foraging opportunities. Maladaptive attraction from artificial lighting can also have potentially adverse effects and increased energy expenditure for migrating passerines and nocturnally active seabirds. Focus areas of study should include the following:

• The extent of displacement for marine birds in response to offshore wind structures
• Variation in marine bird displacement over space and time
• Effects of offshore wind structures on foraging behavior
• Effects of offshore structures on local flight and migratory behaviors
• Impacts of displacement on individual bird and bat fitness
• Artificial lighting's impacts on attraction and disorientation
• Comparing how bat interactions with wind turbines differ onshore and offshore

Habitat-mediated effects

Habitat effects occur when wind turbine structures create substrates that attract benthic organisms and fishes; this phenomenon is often called reef effects. Reef effects can change the structure of local food webs and increase food supplies for some species. Focus areas for future research should include the following:

• Underwater changes around turbine foundations and their effects on marine birds
• Benthic habitat disturbance from offshore wind energy construction and how it affects marine bird fitness
• Changes in ocean conditions in proximity to offshore wind farms and effects on marine bird distributions

Population and cumulative effects

Offshore wind can potentially change the survival and breeding success of birds and bats on a large scale, which could cause population-level effects. Much of the current understanding of the potential effects of offshore wind is based on demographic models of marine birds, as opposed to field studies that collect empirical data. The expected offshore wind buildout in the US Atlantic could expose birds and bats to thousands of turbines with unknown population-level effects. In addition, there is limited understanding of how impacts from offshore wind will interact with other stressors like commercial fishing and climate change. Recommended research priorities for population and cumulative effects should include:

• Population-level impacts for marine bird displacement
• Understanding how bat fatality rates compare onshore and offshore
• Collision risks and relationships to population-level impacts

Research priorities

The authors caution that while the above research priorities are among the most important for offshore wind's effects on birds and bats, other considerations have to be considered, given limited resources. These factors include study feasibility, potential of the research to inform decisions, address urgent needs, focus on the factors with the most significant effect, understanding effects at different spatial/temporal scales, and focus on the most important species. Species prioritization should include the following considerations:

• Species of conservation concern and listed species
• Species most likely to be affected
• Species with adequate existing knowledge (facilitates robust study designs)
• Species with limited knowledge of potential impacts (necessitates more research)
• Species with critical functions in food webs

Study design recommendations

At the end of the paper, Williams and colleagues identify some general study design recommendations to facilitate studying the effects of offshore wind and wildlife. These recommendations include

• Identifying an appropriate study scale and sample sizes to provide appropriate statistical power to detect change over time
• Identifying the most important variables to study is critical for indirect effects and harder to measure
• Distinguishing the effects of offshore wind from other environmental influences. Baseline preconstruction data are critical for understanding the impacts of post-construction operations and activities
• Integrating new and existing monitoring technologies into offshore wind operations to measure impacts, particularly collisions
• Standardize data collection to compare results across studies and prioritize data sharing among collaborators

Conclusions

Following the above research focus and study design recommendations should result in the most robust and valuable science for understanding offshore wind's impacts on wildlife. Limited funds necessitate meticulous prioritization of scientific research to answer the most important questions for optimal benefit to wildlife.

References

Montevecchi, W. A. (2006). “Influences of artificial light on marine birds,” in Ecological Consequences of Artificial Night Lighting. Eds. C. Rich and T. Longcore (Island Press, Washington, D.C), 94–113. doi: 10.1111/bph.13539. https://islandpress.org/books/ecological-consequences-artificial-night-lighting#desc

Robinson Willmott, J., G. Forcey, and M. Vukovich. 2023. New insights into the influence of turbines on the behaviour of migrant birds: implications for predicting impacts of offshore wind developments on wildlife. Journal of Physics: Conference Series 2507:012006. https://iopscience.iop.org/article/10.1088/1742-6596/2507/1/012006

Van Doren, B. M., Horton, K. G., Dokter, A. M., Klinck, H., Elbin, S. B., and Farnsworth, A. (2017). High-intensity urban light installation dramatically alters nocturnal bird migration. Proc. Natl. Acad. Sci. U.S.A. 114, 11175–11180. doi: 10.1073/pnas.1708574114. https://www.pnas.org/doi/full/10.1073/pnas.1708574114

Williams, K. A., J. Gulka, A. S. C. P. Cook, R. H. Diehl, A. Farnsworth, H. Goyert, C. Hein, P. Loring, D. Mizrahi, I. K. Petersen, T. Peterson, K. M. Press, and I. J. Stenhouse. 2024. A framework for studying the effects of offshore wind energy development on birds and bats in the Eastern United States. Frontiers in Marine Science 11:1-18. https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2024.1274052/full