Offshore wind farms have their bright and dark sides

Wind has been used by humans for centuries as a powerful source of power. Even today it plays an important role in the production of clean, renewable electricity. All you have to do is find a site that meets a number of requirements and install wind farms. And you can start producing. Only are you sure it’s 100 percent environmentally friendly?

Offshore wind farms are not just about benefits

In order to generate wind energy, giant turbines are installed, which require the right conditions, such as the availability of large, open spaces and unrestricted exposure to air movement. Such conditions are most often found in the seas and oceans. The number of offshore wind turbines is growing around the world, especially in the Chinese and European seas. This is an important part of energy security, but not without environmental impact. Wind turbines slow down the wind, disrupt physical and biochemical processes in marine waters, and consequently the structure and functioning of organisms. Awareness of these phenomena and cooperation between scientists and business can help develop technologies and solutions to reduce the potentially negative effects of wind power while maximizing its benefits.

Wind power

The use of wind for energy production has a long tradition, as exemplified by sailing ships or windmills. The latter, invented in Persia in the 9th century, were widely used in Europe from the 12th century onward, mainly for grinding grain. They were the primary source of energy until the end of the 19th century and were built en masse until the Industrial Revolution, when they were supplanted by steam mills, internal combustion engines and then electric motors. After World War II, the centuries-long history of wind mills came to an end.

Today, in most countries around the world, the most important sources of energy are fossil fuels, namely coal and oil. Until the 1970s. In the 1970s. They were cheap and their use was strongly promoted. However, depleting raw material resources and rising prices have made us recognize the need to promote renewable energy sources in recent years. Wind has returned to favor, becoming, along with solar, water or geothermal, an important component of the energy mix.

Wind on land, wind at sea

Efficiently capturing wind energy and converting it into electricity requires suitably large devices, called turbines. They can vary in design [1], but the most common are horizontal-axis turbines, that is, tall towers equipped with a rotor and three blades. Such installations require a lot of space. They were originally installed on land, but for more than 30 years solutions have been available to build them at sea as well.

And offshore and ocean areas are particularly attractive for such investments, as they offer open space without obstructions such as mountains, trees or buildings that would interfere with wind flow. In addition, winds are stronger and more regular over the seas than over land, so offshore turbines generate 2-3 times more energy than those on land. It is hardly surprising, therefore, that interest in exploiting the area is growing.

Since the first offshore wind farm was installed in 1991, there has been a systematic and significant increase in their number and capacity, especially evident after 2001. Over the past 10 years, the use of offshore wind farms has increased by 1,000 percent. The development of technology also means that they are being erected farther and farther from land and deeper and deeper. Currently, we are talking about depths of more than 25 meters, at an average distance of 40 kilometers from the shore, and it is expected that by 2030 these rates will even double [1].

Despite providing valuable renewable energy, offshore wind farms have environmental impacts on a scale and scope that are not yet fully recognized [2-4]. It is therefore worth taking a closer look at the effects of installing these structures, seen especially in, which these structures can have on the atmosphere and ocean life.

Wind of change, wind of change – how farms are modifying the seas

Water in the seas and oceans (as well as in other bodies of water) is in constant motion. This movement takes place both horizontally and vertically, and is driven by factors such as temperature and salinity differences (thermohaline circulation), winds (surface circulation) and tides. Horizontal movements (ocean currents) are essential for energy exchange and equalization of global temperatures. The rising of warmer waters over colder ones and less saline waters over more saline ones leads to stratification, or layering. Vertical movements of water are responsible for the transfer of nutrients and planktonic organismsdownwelling orupwelling in the water column; stratification limits this transport, causing them to accumulate in layers with different properties.

Offshore wind farms, by affecting air and water movements, disrupt these natural rhythms and processes. Windmill turbines slow down the speed of passing air masses by up to 30 percent. Behind them, an unstable field is created with lower wind speeds and higher turbulence than in neighboring areas. A so-called aerodynamic footprint effect is created, which affects not only the atmosphere, but also the surface of the seas, slowing down water currents. As a result, a significant reduction in wind speed can disrupt the circulation of the ocean, and therefore the mixing and stratification of waters over a large area. The effect is greater the more turbines are operating in one place.

Also, the wind turbine support towers themselves present physical obstacles to ocean currents, which are much slower behind the structures. Surface friction increases turbulent mixing of the waters, which further disrupts natural stratification. All of this affects the distribution of temperatures, salts and nutrients in the water around wind farms and has consequences for marine life.

In addition, the construction and operation of wind farms is associated with increased noise levels, significant interference with the structure of bottom sediments, their resuspension and the remodeling of morphological structures. This also leads to significant changes in biological assemblages. It’s hard not to notice when an excavator drives into your house.

Marine life in the shadow of turbines

The impact of wind farms on marine ecosystems is complex and not fully recognized. The best studied is the impact of these installations on birds. Quite a bit of research has been devoted to collision risk analysis and changes in population dynamics and migrations.

The impact of noise and mechanical habitat destruction on benthic organisms, fish, marine mammals or birds is often raised. Noise interferes with the echolocation ability of whales; modifies the behavior of fish, impairing their hearing and communication abilities, forcing them to flee their feeding and breeding sites; and can cause changes in the behavior of seals, porpoises and dolphins, with disturbance effects recorded at distances of up to 20 kilometers from the noise source (especially generated at the construction stage of the farms). On the other hand, many mammal species adapt to the noise levels emitted by the farms during their operation.

Studies are also available that indicate that the migration of some organisms, such as fish, is disrupted by the magnetic field surrounding electric cables for power transmission.

But the ecological effects of wind farms can also be more subtle and less obvious at first glance, though no less fraught. Disruption of natural water movement and stratification affects the availability of light and nutrients necessary for the growth of phytoplankton, which form the basis of marine trophic networks. This can affect the entire food chain in a cascading effect – a change in one element in the ecosystem affects all other groups of organisms, including fish, mammals and birds, and even human activities such as fishing.

As a result, wind farms constructed offshore can alter the biodiversity of the entire area in which they are installed, and even reach much further.

The devil not always scary

Despite the negative impacts of wind farms on marine ecosystems, offshore energy production can also have positive effects. The scientific literature gives examples mainly concerning fish and macroinvertebrates [2, 3]. One such example is mooring structures, which can function like artificial reefs. They are a particularly attractive place for bivalves, which in turn provide shelter and food for small crustaceans, such as gudgeons. These, in turn, provide food for fish and other predators. In this way, through ecological succession and interconnectedness, the biodiversity of artificial reefs can be significantly higher than on a homogeneous seabed.

The production and availability of benthic species on such reefs will increase the availability of food for higher trophic levels. Increased fish abundance and diversity are often observed at offshore farms. In addition, the ban on trawling activities within and near offshore farms for safety reasons further reduces pressures on fish and contributes to their productivity. This, in turn, attracts birds. In conclusion, the farms may constitute a kind of biological hot-spot.

And so worth it, as long as it’s with your head

Wind turbines produce almost free renewable energy, do not contribute to greenhouse gas emissions, and can operate both on land and at sea. Admittedly, if improperly designed and sited, they can negatively affect human health, the environment and the landscape, but aeroenergy, as with everything, should be handled with care.

The ecological risks posed by the negative impacts of wind energy facilities can vary from area to area, depending on the environmental characteristics and biological communities of a given ecosystem (e.g., the presence of migratory bird species that are particularly sensitive to wind turbines). Some species also show varying degrees of resistance to environmental nuisances resulting from the presence of the farms, e.g. herring have been shown to be highly sensitive to noise generated by turbines, while seals can adapt to it. Identification of potentially significant impacts is therefore case-specific. In addition, the environmental impact of a wind farm will also depend on its initial condition and the resilience of the area.

As many researchers emphasize, demonstrating the negative impact of wind farms on marine ecosystems is not meant to question their potential as an effective source of clean and renewable energy. Instead, it is important to recognize the potential ecological impacts that the expansion of the sector may cause on a local and regional scale. This knowledge should contribute to the development of technologies and the implementation of laws that should be directed at reducing these negative effects, taking into account the environmental, social and economic benefits of reduced fossil fuel emissions.

In the article, I used, among others. z:

[1] Buczkowski R., Iglinski B., Cichosz M., 2014. aeroenergy technologies. Scientific Publishing House of Nicolaus Copernicus University, Toruń
[2] WWF-Norway, 2014. Environmental Impacts of Offshore Wind Power Production in the North Sea. A Literature Overview; https://tethys.pnnl.gov/sites/default/files/publications/WWF-OSW-Environmental-Impacts.pdf
[3] Galparsoro I., Menchaca I., Garmendia J.M. et al., 2022. Reviewing the ecological impacts of offshore wind farms. npj Ocean Sustain 1, 1-8. https://doi.org/10.1038/s44183-022-00003-5
[4] Benkort D., Christiansen N., Ho-Hagemann H.T.M., et al. 2024. How Do Offshore Wind Farms Affect the Ocean? Front. Young Minds. 12:1336535. doi: 10.3389/frym.2024.1336535