How would the proposed Humboldt offshore wind project affect birds and bats?
Relative to onshore and near-shore habitats, there are currently thought to be fewer bird and bat species that live in offshore ocean waters, and studies are underway (1) to better understand use of the area and potential risks associated with offshore wind. Additional studies are planned to last for the next several years in order to gain a fuller picture of the offshore ecosystem. As part of the offshore wind planning and permitting process, we are actually learning more about seabirds right now than we have ever known before.
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Some winged species are thought to be at low risk from collisions because their flight patterns place them outside of the blade swept area (3) (the area of space that wind
![Marbled murrelet (Brachyramphus marmoratus).](https://static.wixstatic.com/media/edfe67_d1b4be2e89044419a8e5d16d018264f1~mv2.jpg/v1/crop/x_53,y_0,w_1095,h_564/fill/w_337,h_167,al_c,q_80,usm_0.66_1.00_0.01,enc_auto/Marbled_murrelet_edited.jpg)
Marbled murrelet (Brachyramphus marmoratus).
Source: OSU via Wikipedia (CC BY-SA 2.0) (2)
turbine blades move through), which begins several hundred feet above the ocean’s surface. Put simply, many avian species typically fly well below the turbine blades and will be at a very low risk of impact. A 2024 study (4) using a thermal tracker found that 79% of the birds tracked flew below the swept area of the hypothetical turbines. Other species, such as geese, are more likely (5) to fly at an altitude that puts them at risk of flying within the blade swept area, although it is currently unknown how they would react to the presence of turbines. Some species are likely to simply avoid the turbines (6) by flying around them, as has been recorded in European offshore wind farms.
For impacts to all species and ecosystems, we advocate for avoidance, minimization, and mitigation (AMM) — in that order — where the highest priority should be given to avoiding project impacts, then minimizing impacts that may occur, and finally mitigating impacts that do occur. Despite the risks to avian species, the National Audubon Society supports (7) responsibly-sited offshore wind energy projects because the benefits to species that are being impacted by climate change outweigh the potential direct harm to individual birds or bats. To learn more about the impacts of climate change on bird species visit the Audubon's website Survival by Degrees: 389 Bird Species on the Brink. (8) That website will tell you, for example, that under 1.5 degrees of warming only two Humboldt County (8) bird species are at high risk of extinction due to climate change but under 3.0 degrees of warming 40 species are.
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Click here to read more about potential impacts to seabirds due to floating offshore wind in California (11) from the California Ocean Science Trust in July 2024.
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References
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Adams, J., Felis, J., Kelsey, E., and White, L. (2023, May 11). Marine birds of the California Current and studies to inform offshore renewable energy. California Coastal Commission. https://documents.coastal.ca.gov/assets/upcoming-projects/offshore-wind/Th4/Th4-Adams.pdf
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Nelson, K. and Cushing, D. (2021, May 7). Marbled murrelet [Image]. Wikipedia. https://en.wikipedia.org/wiki/Marbled_murrelet#/media/File:Marbled_murrelet.jpg
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Bastawrous, M. (2015, May). Structural Dynamic Modeling of Wind Turbine Blades. Research Gate. https://doi.org/10.13140/RG.2.1.1965.9683
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Schneider, S.R., Kramer, S.H., Bernstein, S.B., et al. (2024, April 24). Autonomous thermal tracking reveals spatiotemporal patterns of seabird activity relevant to interactions with floating offshore wind facilities. Front. Mar. Sci., 11. https://doi.org/10.3389/fmars.2024.1346758
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Weiser, E.L., Overton, C.T., Douglas, D.C., et al. (2023, October 7). Geese migrating over the Pacific Ocean select altitudes coinciding with offshore wind turbine blades. Journal of Applied Ecology, 61: 951-962. https://doi.org/10.1111/1365-2664.14612
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Desholm, M. and Kahlert, J. (2005, September 22). Avian collision risk at an offshore wind farm. Biology Letters, 1(3): 296-298. https://doi.org/10.1098/rsbl.2005.0336
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Haney, J.C. (2023, March 10). What Offshore Wind Energy Can Teach Us About Seabirds. Audubon. www.audubon.org/news/what-offshore-wind-energy-can-teach-us-about-seabirds
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​Audubon. Survival by Degrees: 389 Bird Species on the Brink [Website] https://www.audubon.org/climate/survivalbydegrees/flyway/pacific
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Audubon. Survival by Degrees: 389 Bird Species on the Brink, Humboldt County Page [Website] https://www.audubon.org/climate/survivalbydegrees/county?zipCode=95503
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Pereksta, D.M. (2023, May 17). Birds and Offshore Wind Energy Development: BOEM’s Avian Study Strategy to Assess Data Needs and Effects [Video]. U.S. Bureau of Ocean Energy Management. https://drive.google.com/file/d/1JNJElljx0k3xcfXzrC_HgiW8BnbOWNdr/view
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California Ocean Science Trust. (2024, July). Impacts to Seabirds. www.oceansciencetrust.org/wp-content/uploads/2024/07/OST-Science-Factsheet-3-Seabirds-Final.pdf