An Offshore Wind Farm Does Not Start with Wind Turbines

Discussions about offshore wind energy often focus on the turbines. In reality, the planning of a potential offshore wind farm is preceded by extensive studies examining everything from bat migration routes and seal feeding grounds to marine seabed habitats. 

Offshore wind energy has become increasingly prominent in Estonia’s energy policy discussions in recent years. On the one hand, it is seen as an opportunity to increase renewable energy production and strengthen energy security. On the other, there are legitimate questions about the potential impact of offshore wind farms on the marine environment and the species that inhabit it. Finding answers to these questions begins with comprehensive studies. 

One of the key characteristics of offshore wind energy is that wind conditions at sea are generally more stable than on land, making it an important potential addition to future renewable energy production. This is precisely why it is essential that any potential developments are based on thorough environmental and technical studies and take the specific characteristics of the marine ecosystem into account. 

The joint Estonian-Latvian ELWIND project is preparing for potential offshore wind energy development in the Baltic Sea. In Estonia, the project is being implemented by the Environmental Investment Centre together with its partners, assessing whether the marine area west of Saaremaa is suitable for offshore wind energy production and under what conditions an offshore wind farm could be developed there. To this end, both environmental and technical baseline data are being collected. 

Environmental studies cover virtually the entire marine ecosystem – from bats and birds to seals, fish, seabed communities and water quality. Their purpose is to establish a reliable baseline of the area’s wildlife and marine environment, enabling potential impacts to be assessed and providing a science-based foundation for future decisions. 

International experience shows that the results of such studies can directly influence development planning. In several European countries, studies have led to changes in turbine locations, adjustments to cable routes, or the scheduling of construction activities in ways that help reduce impacts on birds, marine mammals and fish populations. 

Birds, Bats and Marine Mammals 

Although bats are usually associated with land, some species also travel over the sea, using it as a migration corridor and feeding area. Their activity and species composition are therefore monitored to assess potential collision risks and to understand how future turbines could affect their behaviour. 

If studies show that the planned development area overlaps with an important migration corridor, or that bat activity is particularly high during certain periods, this can be taken into account when planning turbine locations. Where necessary, seasonal or temporary operational restrictions can also be introduced, such as shutting turbines down at night during periods of increased risk. 

Bird surveys are carried out over a two-year period and combine aerial surveys, radar monitoring and telemetry. This provides information on bird abundance, distribution, migration routes and flight altitudes. The aim is to determine how important the study area is for birds as a feeding, stopover or migration area and how a potential offshore wind farm could affect them. 

The results help determine whether certain areas should be avoided, whether turbine locations should be adjusted, or whether mitigation measures should be introduced to reduce impacts on migration and feeding areas. 

Marine mammal studies focus primarily on grey seals, while also paying attention to ringed seals and harbour porpoises. Grey seal movements are tracked using satellite transmitters to map their feeding grounds, migration routes and habitat use. In addition, the number of grey seal pups at breeding sites near the ELWIND area is assessed using aerial surveys and drone imagery. Harbour porpoise occurrence is monitored using underwater acoustic devices that record their characteristic sounds. The studies also assess potential impacts caused by construction noise and increased vessel traffic. 

If studies show that construction activities could disturb important breeding or feeding areas, the timing of construction can be adjusted and, where necessary, the boundaries of the development area or technical solutions can be modified. 

Fish and the Seabed 

Fish surveys are also an important part of the studies. Over two consecutive years, data are collected on fish species, their abundance and distribution, while potential impacts of an offshore wind farm on fish habitats, migration and fisheries are assessed. Particular attention is being paid to the migration routes of spring-spawning herring, in order to determine whether they overlap with the planned wind farm or cable routes. 

If, for example, the main migration routes of spring-spawning herring overlap with a planned cable route, alternative routing options or different timing of construction activities can be considered to reduce impacts on fish populations. 

To gain a comprehensive picture of the marine environment, researchers are studying seabed communities, habitats, sediments and water quality. Benthic flora and fauna are being mapped, sediment composition is being analysed, and the current state of the marine environment and its natural seasonal variations are being recorded. 

Based on these data, models are being developed to assess how future turbines could affect waves and currents, which transport nutrients and oxygen essential to marine life. The studies also help assess construction-related impacts, such as sediment disturbance, as well as potential long-term changes that could result from the operation of an offshore wind farm. 

If studies identify sensitive habitats, this may mean that turbine or cable locations need to be changed or those parts of the area should be excluded from development. 

Marine Conditions and Technical Studies 

In addition to extensive environmental studies, the seabed and marine conditions are also being examined from a technical perspective. Geophysical and geotechnical surveys are used to map seabed characteristics and determine what types of foundations could be installed in the area. 

Meteorological and hydrographic measurements provide data on wind, waves and currents. These data help researchers understand the natural conditions of the area, as well as the opportunities and constraints involved in planning a potential offshore wind farm. Together with the environmental studies, they provide the scientific basis for assessing the suitability and potential impacts of the development. 

In addition to assessing the specific development area, the studies will also expand knowledge about marine life in Estonia’s waters more broadly. Many areas of the Baltic Sea have so far been relatively poorly studied, and the data being collected will be valuable not only to the project itself but also to researchers, conservationists and future marine spatial planning and management. 

It is also important to assess the cumulative effects of different developments. The Baltic Sea is a limited and sensitive environment where individual projects cannot be considered independently of one another. Unlike on land, changes occurring at sea can spread over considerably larger areas through currents and waves, and their effects may only become apparent in monitoring data years later. This makes it particularly important to understand how the marine ecosystem functions before potential developments are planned and what changes different activities could cause in combination. 

Once the studies are completed, their results will form part of the evidence base for the environmental impact assessment and planning process. They will be used to assess whether and under what conditions the area could be used for offshore wind energy production. The studies do not automatically mean that the development will go ahead. They may also lead to the conclusion that a particular area is not suitable for use in the planned way. 

Offshore wind energy development raises questions related to nature conservation, fisheries, local communities, and energy security. The ELWIND studies provide the environmental and technical data needed to address these questions. Based on this information, it will be possible to assess both the suitability of the marine area for offshore wind energy production and the potential impact of a development on the marine environment. 

That is why planning an offshore wind farm begins with gathering knowledge, not with construction. The better we understand the marine ecosystem before decisions are made, the more responsibly potential developments can be planned. A good offshore wind farm is not created through compromises at nature’s expense, but through knowledge that helps find a balance between renewable energy production and protecting the marine environment. 
 

Author: Aivi Allikmets, ELWIND Project Manager.

An article was published in Saarte Hääl on 12 september 2026.