Life-cycle impact assessment of offshore wind energy development on migrating bird diversity in the North Sea
Emma Critchley and co-authors have just published an article in the Journal of Applied Ecology, based on work conducted in the MARCIS project. The publication focuses on the potential impacts of offshore wind energy developments in the North Sea for the hundreds of millions of seabirds and migrating birds that cross it every year.
Offshore wind energy is a stressor with potentially high impact on birds that use the marine environment. The development of offshore wind energy is rapidly expanding in the North Sea due to ambitious government targets for reducing carbon emissions. Birds on migration, which could cross offshore wind farms in large numbers, are particularly at risk. Assessing this risk is challenging due to the lack of data and the difficulties of monitoring offshore. The results presented in this publication address one of the key aims of the collaborative MARCIS project - to assess the impacts of offshore wind farms on birds.
Migrating birds can be impacted by a) direct collision with the turbine or blades, b) disturbance from the area around the turbine, or c) barrier effects which cause migrants to fly much longer distances around or over a wind farm. The authors assessed these impacts by using a life-cycle impact assessment to evaluate the impacts of current and future (up to 2030) offshore wind energy developments in the North Sea on migrating birds from Norway.
What the research shows
Many bird species migrating across the North Sea are at greater risk from disturbance and barrier effects when encountering an offshore wind farm, compared to the risk of colliding with a turbine. Whilst disturbance and barrier effects do not cause direct mortality, these additional energetic costs can have long-term impacts (i.e., affecting future survival and reproduction), particularly when birds encounter multiple wind farms along their migration pathway. Birds on migration are most at risk when crossing between Southern Norway and Denmark, as well as along the Swedish, German and Dutch coasts, where high bird migration density intersects with multiple large offshore wind farms that are planned for development.
Cumulative impact for all bird groups if a 15 MW turbine was placed in each grid cell for all impacts combined. High impact values = yellow/ green, low impact values = blue. White outlines = footprint of all existing and future wind farms up to 2030.
Collision, disturbance, and barrier effects for wind farm developments in the North Sea have the greatest impact on migrating waterfowl, raptors, gulls, waders, and seabird species. These are the same birds that are at greatest risk from onshore wind development in Norway. Many species from these groups are already listed as threatened on the Norwegian Red List and additional pressures both on their migration routes as well as at their breeding grounds will likely have negative population-level impacts.
Implications for management
There is a risk that if wind farms are placed too close together within a core bird migration area the cumulative impact due to barrier effects could be greater due to the large additional distances travelled by the migrating birds and subsequent energetic costs. The footprint and siting of future wind farms in the North Sea beyond 2030 should be carefully considered in this context to ensure that we are not creating excessively large barriers across core migration routes.
This life cycle impact assessment could provide a useful tool for continued assessment of cumulative impacts to migrating birds from offshore wind energy in the North Sea, and in other regions, as the industry rapidly expands. It can also be applied at a more local scale, for example when comparing estimated impacts across potential wind farm sites to mitigate unintended negative consequences on migrating bird populations.
You can read the full text of the publication here: Critchley, E.J., Nilsson, A., Helberg, M., May, R., 2025. Life-cycle impact assessment of offshore wind energy development on migrating bird diversity in the North Sea. Journal of Applied Ecology, 62(6). https://doi.org/10.1111/1365-2664.70087
MARCIS has also produced a knowledge brief which presents the contents of the article to a wider audience, particularly potential users of the MARCIS tool. You can find it under: Project Materials - Knowledge Brief #1