Author: Hana Ketley

Offshore wind farms (OWFs) are areas with multiple turbines, often located in relatively shallow water just off the coast. The energy produced by the force of the wind is clean and renewable but, often, such climate change solutions come with trade-offs. Research around these areas has shown that they can impact surrounding habitats and ecosystems both positively and negatively.

Climate change prevention vs biodiversity protection

Policies and strategies for fighting climate change can sometimes ignore or under-emphasise biodiversity protection. For example, a pledge made at COP26 in 2021 to halt net deforestation by 2030 does not actually prevent the cutting down of forests, but instead requires that forest loss should be replaced ‘sustainably’. However, replacing primary forests with new growth has negative consequences for biodiversity, as ancient woodlands are highly complex ecosystems. New growth is less able to support the same level of biodiversity and it would take decades for an area to develop back into a climax community. Therefore, while this pledge may help to fight climate change by potentially stabilising or even increasing global forest cover, it would allow for the continued negative ecological impacts of deforestation.

Wind farms face similar dilemmas. They produce clean and renewable energy, without the negative impacts on the climate of traditional energy sources such as coal and gas, but they have been shown to impact the surrounding environment.

Negative impacts of offshore wind farms

Two phases can potentially cause disturbance to wildlife: the construction phase and the operation phase. Some species may be impacted during the construction phase but are able to recover and are unaffected by the general noise of the operation phase, but some are impacted by both, thus creating long-term changes in the ecosystem. Additionally, wind turbines do not have an infinite lifespan, and may need replacing as frequently as every 20-25 years. While this may not involve a full replacement, it would involve some level of construction and therefore disturbance.

The impacts of wind farms can be through collisions, displacement, noise, destruction of habitat, change in hydrology and more. One new report, however, found that seabirds off the UK coast are better at avoiding wind turbine blades than previously thought. Researchers monitored how birds behaved in Aberdeen Bay for two years using radar and cameras. The results showed the birds adapted to the rotor blades from approximately 120 meters, becoming increasingly precisely adapted the closer they came to the rotors. During the two-year study, there wasn’t a single collision between the birds and the rotor blades. However, collisions are not the only way wind farms can affect wildlife.

A recent study has found that populations of red-throated divers decreased by more than 90% in areas where OWFs were built. The data, gathered by German scientists, looked at population numbers in the North Sea before and after five OWFs were built and found that numbers were up to 94% lower within half a mile of the turbines after they were installed. One farm in particular showed a 99% decline in population numbers. The impact is also more widespread, with an average decline of almost half of bird numbers up to six miles away from the turbines. The cause behind this decline is thought to be due to the effect turbines have on their hunting techniques. Their formerly large foraging area has been split into smaller units by these offshore farms, restricting their movements when foraging for highly mobile prey.

Red-throated divers are not the only species that are being affected by OWFs. A study assessing the vulnerability of marine populations to offshore wind farms in 2013 identified a number of other seabirds that are potentially at risk, including gulls, white-tailed eagles, northern gannets, skuas and common scoters. More recent studies highlight the impacts on long-tailed ducks, common eiders, razorbills and common guillemots, such as general avoidance, changes in migration patterns and lower abundance around wind farms. The increased energy cost of avoiding wind farms could potentially impact survival and reproductive success, depending on the length and frequency of the flight, as well as the characteristics of the species.

While birds are often the focus of studies into the environmental impacts of OWFs, numerous studies have found that marine mammals such as porpoises, whales and dolphins, as well as fish and marine invertebrates, are affected. Many types of offshore wind turbines need foundations that are placed deep into the seabed. By drilling the sea floor, any benthic marine habitats in the surrounding area could be destroyed, while the displaced sediments can hang in the water column impacting filter feeders and photosynthetic organisms. Once the sediment settles, it can also smother many bottom-dwelling organisms, preventing them from feeding.

Furthermore, the noise pollution from the construction can threaten marine organisms, as it interferes with the communication of species such as porpoises, dolphins and whales. These species rely heavily on their hearing for orientation, hunting and communication between individuals. Prolonged exposure to loud noise, which even the normal operation of turbines can produce, leads to hearing loss and stress, increasing their vulnerability to diseases, while also combining cumulatively with the impacts of other pressures such as pollution and reduce food availability. Fish are also affected by this prolonged exposure.

Stress from these pressures leads to behavioural changes, and affects general movement, feeding patterns and migration. It can also impact fecundity and mortality rates. Due to this, as well as changes in the physical or chemical characteristics of the habitats surrounding wind farms, ecosystem structures may change because of alterations in species composition or abundance. This can impact the functions of the ecosystem, having widespread impacts on the surrounding environment, as well as the industries that rely upon it, such as fisheries.

Positive impacts of offshore wind farms

Wind turbines and their foundations, though destructive to construct, provide structures that become artificial reefs for corals and other sessile aquatic organisms such as sponges, seaweeds, mussels and anemones. This increase in the distribution and abundance of certain species, such as invertebrates, can attract other species that are higher in the trophic level, such as fish.

Certain farms also ban fishing, which can reduce pressures within the boundaries of the farm. This, along with the ecosystem supported by the artificial reef system, can provide a haven for fish that are usually heavily overfished. This increase in food availability can, therefore, have a positive impact on many species in higher trophic levels, such as seabirds, but the impact varies from species to species and often from farm to farm.

Advantages of onshore vs offshore wind power

Onshore wind farms are cost-effective, as they’re one of the least expensive forms of renewable energy and are far less expensive than offshore wind power. They are also easier to construct and maintain, unlike offshore farms, where higher wind speeds, strong seas and other accessibility issues can make maintaining these farms more challenging. However, offshore wind farms are more efficient, as higher, more consistent wind speeds mean that fewer turbines are needed to produce the same amount as onshore farms. Additionally, there is more space to construct farms offshore than onshore, with a reduced effect on local people.

What are the solutions?

As the world moves towards carbon net zero in an effort to fight climate change, wind power is going to be more heavily relied upon, meaning the construction of more wind farms. With the construction of these structures in the ocean, there will always be some negative impacts, but there are things that can be done to mitigate some of these. A balance needs to be found between efforts to meet net zero and protecting our environment.

Continuing to monitor and assess the impacts of existing wind farms can inform the ecological strategies of future builds. By improving our understanding of how these farms impact the environment and ecosystem, future projects can be adapted to reduce these impacts. This research needs to be properly funded and shared globally, with stringent legislation that is updated in response to findings. These studies should be rigorous and consistent, avoiding underestimations that could allow the continued threat to the environment but steering clear of overestimations which could hinder further development of clean energy through wind farms.

Using data from fisheries can indicate where research is needed, as an increase or decrease in catch around wind farms suggests ecological changes. However, this would mean only the impacts that affect commercial fish would be investigated and impacts on other, non-commercial species may be overlooked. Therefore, other monitoring methods are also needed, which will involve funding from both private and government sources.

In the UK, Natural England has called for new OWFs to leave nature in a better state than before its construction, avoiding any irreparable damage to the environment. The approach, published in June 2021, set out how these farms can play a vital role, not only in tackling climate change, but also in nature recovery. Similar to Biodiversity Net Gain, which requires new developments on land in England to ensure that habitat is 10% better after building than before, Natural England is seeking to ensure that new OWF projects ‘build in’ plans that will enhance nature and protect the environment from the pressures mentioned above. The approach outlines the objectives and actions that Natural England will focus on, in partnership with others such as Defra’s Offshore Wind Enabling Actions Programme. These include:

• Aiming for each development to leave nature in a better state.
• The advanced introduction of strategic, to-scale and evidence-based measures that will compensate for environmental harm.
• Monitoring to inform stronger, evidence-based impact assessments, promoting the use of environmentally sensitive design, construction and operation.
• The development of an environmental sensitivities map that is easy-to-use, so that planners and developers can make sure OWFs and their cables avoid causing irreparable damage to the environment.

Other mitigation options include the arrangement of turbine clusters, as certain patterns can minimise barriers to movements, such as creating corridors within the farms to allow birds to pass through rather than having to extend their flight to go around extensive concentrations of turbines. Advances in technology have also given rise to options such as floating wind farms, which would reduce the impact on the sea bed, as well as potentially reducing the construction phase; and multi-purpose interconnectors, which would allow multiple offshore farms to be connected to the shore, rather than individual wind farms, which would reduce the impact of cable laying.

Other renewable energy options

Other renewable energy options include hydropower, solar power, biomass and geothermal energy. Solar power is an important source of renewable energy and can be placed on areas such as roofs, to reduce the space needed, but there are environmental implications for large-scale solar energy production, including aluminium demand. Hydropower, such as wave and tidal power, has future potential but is not yet widely employed commercially.

These could also have ecological impacts, however. For example, large-scale wave energy converters could cause changes in water velocities, which may impact sediment transport, coastal erosion and the increase of sediment deposition. Additionally, barriers such as dams radically change the typography and environment of rivers, with widespread ecological implications. Burning biomass, often from agricultural waste, releases carbon dioxide. While the plants that are grown as the source of the biomass can capture almost the same amount of CO2, the burning smoke can also contain harmful pollutants such as carbon monoxide, as well as producing ash which can contain high concentrations of various heavy metals such as lead and cadmium, which would need proper disposal. Geothermal energy produces both water and air pollution, such as arsenic, mercury, nickel, methane, ammonia and carbon dioxide. It also produces hazardous waste that would require safe disposal and requires a large amount of water for purposes such as cooling.

It is clear that all renewable energy comes with some negative environmental implications. However, the pollution and greenhouse gases produced are far less than non-renewable energy sources such as fossil fuels. Fossil fuels do substantially more harm than renewable energies, therefore the world must continue to expand and improve its renewable energy endeavours, while focusing on reducing and mitigating their negative environmental impacts.

Summary

• Climate change strategies often overlook the protection of biodiversity, with wind farms producing clean and renewable energy but having serious impacts on the environment and ecosystems surrounding them.
• Both the construction phase and the operation phase of offshore wind farms (OWF) cause disturbances, such as population declines, changes in general movement, feeding patterns, migration, fecundity and mortality rates.
• OWFs also have positive impacts, creating structures that form artificial reefs, and increasing the abundance of certain species such as corals, mussels and anemones, which then attract species in higher trophic levels. Certain farms also ban fishing, creating havens for commercially important fish.
• A balance needs to be found between the effort to meet net zero through creating more clean, renewable energy and the protection of our environment.
• Continuing to monitor and assess the impacts of existing windfarms, plus stringent legislation, can help improve the ecological strategies of future farms.
• Natural England has developed an approach that would require new OWFs to leave nature in a better state than it was before construction, avoiding any irreparable damage to the environment. The objectives of this approach include the advanced introduction of strategic and evidence-based measures that will compensate for environmental harm and the development of an easy-to-use environmental sensitivities map, which will help planners and developers make sure OWFs avoid causing irreparable environmental damage.
• All renewable energy sources come with some negative environmental implications but fossil fuels are far worse. Therefore it is important for renewable energies to expand, with a focus on reducing environmental impacts.

References and further reading

News report on the decline of red-throated divers.

The study of offshore wind farms and their effects on birds, published in 2019, and a study assessing the vulnerability of marine bird populations to offshore wind farms, published in 2013.

Report on the study which found that seabirds in the UK are better able to avoid turbines than previously thought.

Natural England’s Approach to Offshore Wind

Wildlife and Wind Farms, Conflicts and Solutions, Volume 3: Offshore: Potential Effects

Wildlife and Wind Farms, Conflicts and Solutions, Volume 4: Offshore: Monitoring and Mitigation