Biodiversity and ecosystems
Datalogging to map the effects of wind farms on seabirds
The construction of wind farms is taking off in the North Sea. This leaves a smaller area for seabirds in which to search for food, as they tend to avoid wind farms. Scientists at Wageningen University & Research are developing a computer model to get a picture of what the loss of foraging area means for the survival of seabirds during the winter.
The Dutch energy transition is taking place to a large extent in the North Sea. However, large-scale development of offshore wind farms has major ecological consequences, not just for marine mammals and fish but also for birds and bats, which may be hindered by wind turbines. Marine ecologist Vincent Hin, who works at Wageningen Marine Research, uses computer models to predict how birds will respond to the loss of foraging area. He explains how that works.
“There are currently five operational offshore wind farms in the Dutch part of the North Sea, but the plan is to have far more. Fitting birds with GPS loggers has told us that some seabirds, such as the gannet, avoid wind farms. It is not clear why they do so, but the result is they can no longer use part of their original habitat, for example to look for food. We want to know what effect that has on bird populations so that it can be taken into account when planning future offshore wind farms.”
“To investigate this, you first need to know how the birds use the North Sea under normal circumstances. Where do they go and what do they do there? In the summer, seabirds are based at a breeding colony and they venture out to sea occasionally to search for food. We have quite a lot of data on this, for example from observations and studies using transmitters. But in the winter, the birds spread out over the sea and we don’t have a good picture of what they do. That’s why we’re working on a computer model that simulates the movements of individual birds in the winter.”
A model always involves making assumptions. For these predictions, we assume birds always make choices that maximise their fitness by the end of the winter, leaving them in the best possible condition to produce as many offspring as possible. We use a ‘dynamic state variable model’ to make the predictions. This model describes individual birds’ energy reserves, which ultimately determine their fitness.
‘We can use this model for other bird species and to investigate other kinds of effects of wind farms’
“We use a simulated map of the food scene of the North Sea, derived from data on counts of birds at sea. Then we try to predict how the birds will use the area. Do they stay in one specific place? Where do they look for food? When do they move off somewhere else? And how are these decisions related to their condition and the amount of food available? After all, the birds’ survival depends on their foraging strategies.” “So far, we have modelled birds’ behaviour in the natural marine environment without wind farms. That tells us what the optimum behaviour is for getting through the winter. In the next phase, we plan to make parts of the habitat inaccessible, simulating the wind farms to see what effect this has on their survival. Do the birds relocate elsewhere, or do they get into trouble? And what determines this? We can play with the wind farm locations, or how scattered they are.”
“The big advantage of a model compared with studying the real world is that you can easily introduce variations; you can’t simply move a wind farm in real life.” “It is hard to say anything about the impact of wind farms at the moment. Intuitively you would think the loss of foraging area would affect the birds negatively, but that depends on the situation. The key thing is which factor is limiting for that bird population. If you look at gannets, for example, last summer 70 per cent of the breeding colony died from bird flu. Now that there are far fewer birds, the foraging area might not have a limiting effect because there is not much competition. In breeding colonies, it may be the case that the number of individual breeding spots is the limiting factor and it doesn’t matter so much what happens in the winter. These are all aspects you need to take into account. At the moment it is not possible to play with these factors in the model because it only simulates the birds’ movements. We are mainly interested in which parameters are most influential.”
‘The computer produces a simulation of the food scene and tries to predict how birds will use the food’
“We need to check the extent to which our model matches the actual behaviour of gannets. To do that, we want to compare our numbers against data from field research on how birds behave around a wind farm. The best thing would be to validate the model by seeing how well it can predict the actual situation. But that is a lot of work because we would need to have field data and link that to information on how much food is available in certain places.”
“In future, it could also be interesting to look at what risks birds are willing to take. That will depend on the bird’s condition and whether food is available in a wind farm. If a bird is very hungry and has no alternative, it is more likely to enter the wind farm area.” “Eventually we hope to come up with something that is used in policy recommendations. Of course we need to be careful
because we don’t yet know how close the model is to the real-world situation. But we can still check to see whether there is reason to be concerned. What is more, we can’t study such effects in field research as that would mean the wind farms are already in position, whereas we want to know beforehand what the effect would be so this can be taken into account in the plans.”
“Additionally, we can use this model for other bird species and to investigate other kinds of effects of wind farms. For example, we suspect collisions with wind turbines could be more of a problem than the loss of foraging grounds for some seagull species. What I personally like most about my research is that we try to capture the mechanisms underlying the patterns we see in the marine environment in our computer models.”
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WHO Vincent Hin, marine ecologist
RESEARCH Modelling foraging movement patterns and predicting effects of habitat loss
TEAM Floor Soudijn, Tobias van Kooten and Daniel Benden, Wageningen Marine Research
MORE INFORMATION This project is part of the Next Level Animal Sciences (NLAS) innovation programme.
Participating researchers of Wageningen University & Research collaborate with various partners to develop new research methods and technologies within the field of animal sciences. NLAS consists of three research directions, namely sensor technology, complex cell systems and data and models.
