Modelling reveals the effects of ten hypothetical offshore wind farms and highlights important knowledge gaps.
A knowledge gap in the green transition
The development of offshore wind is a key instrument in the shift toward renewable energy, but such interventions can also impact marine biodiversity. Seabirds are among the most threatened bird groups globally and are vulnerable to both collisions with wind turbines and displacement from important feeding grounds. Until now, most research has focused on the breeding season, when birds remain in and near their breeding colonies. How offshore wind affects seabirds during the long non-breeding period has, however, been poorly documented.
Lila Buckingham, researcher at NINA and lead author of a recently published article by an international research team, explains that they developed a new model to provide better decision support for future offshore wind development – particularly in northern marine areas where many Norwegian seabird populations spend much of the year.
Individual-based model using tracking data
In the study, the researchers developed an individual-based model (IBM) that simulates the behaviour and movements of seabird individuals during the non-breeding season. The model is based on long-term data from geolocation–immersion loggers collected as part of the SEATRACK project, which provide information about seabirds’ geographical distribution and activity patterns at the population level.
"We simulated individual behaviour, movements, flight altitude, energy expenditure, and interactions with wind farms, including collisions with turbines, displacement from important habitats, and the resulting lethal or near-lethal effects", Buckingham explains.
The model was applied to two Norwegian populations: common guillemot (Uria aalge) from Sklinna and black-legged kittiwake (Rissa tridactyla) from Ålesund. The effects of ten hypothetical offshore wind farms were analysed for both species.
Large variation between species
The results show clear differences between species in how offshore wind power structures affect seabirds outside the breeding season. For common guillemots, the study found that 49.6 % of individuals would experience displacement from habitat due to the hypothetical offshore wind farms. Because the energetic costs of such displacement remain uncertain, the researchers modelled several scenarios. These indicated that potential adult mortality could range from 0 to 5.32 %, and that body mass at the end of the season could be reduced to 97.12 – 99.84 % of the level expected without wind-power impacts.
For kittiwakes, the picture was different. Although 98.9 % of individuals flew through at least one hypothetical windfarm, collisions were predicted for only 0.055 % of the population. This low mortality is mainly explained by the limited overlap between the typical flight altitude of kittiwakes and expected turbine rotor heights for planned developments in Norwegian waters.
Methodological advancement
The study shows that non-lethal effects such as displacement and increased energy expenditure can, over time, influence both survival and reproduction – particularly for species already under pressure. At the same time, the model is a powerful tool for testing different development scenarios and assessing the potential impacts of offshore wind farms on seabird populations outside the breeding season before projects are realised.
"Our model is repeatable and can be adapted for use with other species and other threats in the marine environment, and its results have been used to predict seabird population impacts in the MARCIS tool", says Lila Buckingham.
She and her co-authors also emphasise that the uncertainty surrounding the energetic costs of displacement is one of the most important knowledge gaps that needs to be filled moving forward. Nevertheless, the study represents a significant methodological step forward and can contribute to more sustainable offshore-wind planning, where both climate and nature are taken into account.
Read the article: An individual-based model to quantify the non-breeding season impact of wind farms on seabirds
Contact: Signe Christensen-Dalsgaard