Offshore wind power enables industry to have a renewable and synthetic alternative in terms of energy production. It can be used to expand electricity production and thus meet the growing electricity needs of a technologically constantly developing society. It is clear that offshore wind projects inevitably entail impacts on the environment, particularly aquatic habitats, and these effects, as well as potential disadvantages, must be taken into account at an early planning stage.

What is taken into account when assessing the environmental impacts of an offshore wind power project and how can adverse effects be prevented?

The location of the power plant is one of the most important factors for aquatic nature

In an offshore wind power project, large wind turbines are built, and their impacts affect the seabed, water and above the water level. Electricity transmission requires the installation of cables on or under the seabed. Water turbidity, underwater noise and changes in electromagnetic fields caused by construction work and the operation of the power plant area are examples of impacts that must be taken into account when planning an offshore wind project.

In the assessment, the impacts are divided into impacts during construction and during operation. The placement of an power plant is one of the most essential aspects that must be taken into account in planning. The aim shall be to locate the wind turbine in an area where its impact is as low as possible. For example, bird migration routes, significant fish breeding grounds and all protected habitats, such as sea drift meadows, must be taken into account. The location of the offshore wind farm must not cause a collision risk for birds or harm fish spawning grounds. A challenge in terms of placement is, for example, that fish breeding grounds are located in shallower sea areas, but building in these areas is easier in practice.

Adverse effects can be prevented and even converted into ecological compensation

The significance of aquatic nature as a provider of ecosystem services and the preservation of biodiversity is enormous, for example in fish and fishing. Aquatic nature provides us with protein sources, activities and business that are directly linked to economic interests and fish stocks. Tourism by waterways, summer cottages and boating are also issues to which the effects of offshore wind power are directly linked. In addition to recreational services, clean water and domestic water are gifts of aquatic nature that should be cherished.

Wind turbines built in the sea area bring with them a landscape effect, as in the absence of visual obstacles, the wind turbine can be seen up to tens of kilometres away. In addition to the landscape effect, noise is also a nuisance, which is of course also an essential factor.. When talking about people, the physiological harm caused by noise effects varies from person to person, but noise nuisance also affects nature and species. The actions taken during the start-up phase determine the extent of noise from the construction site. For example, mining or drilling under the sea causes a lot of noise, which is particularly disturbing for marine mammals. Once again, investing is of great importance in terms of the number and extent of adverse effects.

In order to prevent the deterioration of the natural state, the environmental impact assessment of offshore wind power projects must be carried out appropriately in advance. Studies should not be carried out just for the sake of the investigation, but the information obtained from them must be included in the plans so that mitigation measures for potential harm are actually implemented. Thorough and timely planning work can identify opportunities to implement mitigation measures that are as comprehensive as possible, such as minimizing harm during construction and locating cables and power plant construction. In addition, careful planning can identify and plan compensation measures that can be used to create, for example, replacement breeding areas for fish. Voluntary ecological compensation will certainly be applied more and more in projects in the future of offshore wind power , and Sweco also has the necessary expertise for similar design measures.

Mapping and open interaction promote social acceptance of offshore wind projects

At the beginning of the environmental impact assessment, important analysis and planning work is carried out to ensure the success of the wind power projects. In addition to existing research material, the species and habitats of the planned power plant area will be studied by videotaping, sampling from a boat and diving, for example. Extensive research must also be carried out concerning electricity transmission routes. The seabed will inevitably be affected, which is why it is important to investigate the quality of the bottom sediment, for example, in order to determine the risk of harmful substances spreading.

In addition to the above-mentioned measures, the survey can be carried out using various interview methods. Interviews with important stakeholders provide information on the use of the area’s waters, such as fishing. In addition, surveys can be targeted at the residents and users of the areas in order to gain as comprehensive understanding as possible of the factors that have a significant impact on their lives at an early stage.

Investigating water quality and hydrological factors are also essential parts of determining the current state of the marine environment. The aim is to get an idea of the water chemistry in the area, what kind of waves and currents are formed in the area, how the water is deposited, what the state of the sea area is, and whether there are any ongoing plans that would restrict activities in that area. The Environmental Administration publishes plans related to water and marine management, which bring with them certain guidelines. They report, for example, on the state of marine areas and the measures that should be taken in the area in question to improve the state of the sea area. In practice, all possible open research data, statistical data and spatial data, as well as the utilisation of various models and models, are decisive factors for mapping. In addition to this, there is a lot of information that cannot be obtained from ready-made materials. In these cases, participatory methods, for example through interviews, help to clarify the essential aspects of the project.

Participatory activities and active interaction promote the social acceptability of projects; Communicating more openly about the planning and progress of projects encourages people to take a more active role in promoting sustainable energy production.

Research will play an important role in future projects

Although there is a lot of existing data for the survey, as well as measures that will also go a long way in acquiring the information missing from the data, it must be remembered that this is a relatively new phenomenon. If offshore wind power is examined, for example, in the Northern Baltic Sea region or in Finnish waters, its construction history does not go very far. Therefore, the importance of research cannot be emphasised enough.

There are many things on which there is not enough research data, such as the combined effects of projects located in close proximity to each other on both aquatic nature and, for example, birds. In the EIA process of wind power, experts make the best use of existing information, but research data and monitoring data over increasingly long periods of time are needed and should be collected more and more in order to build the future of offshore wind power on the ever-growing needs of society, while  taking sustainable development and aquatic nature into account and keeping in mind solutions that increase ecological compensation.

Jaakko Leppänen, Water Specialist FT, jaakko.leppanen@sweco.fi
Janne Tolonen, Water Specialist,  janne.tolonen@sweco.fi

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