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Offshore Renewable Energy & Marine protection and restoration

The ambitious EU-wide objectives for a rapid shift towards climate neutrality are resulting in an increase in the number of Offshore Renewable Energy (ORE) installations, and in particular Offshore Wind Farms (OWF). Clear objectives for the sectors were set at EU and sea-basin levels [1][2]. ORE installations can generate environmental effects throughout their life cycle: pre-construction geotechnical studies, construction phase, operation phase and decommissioning phase. The main impacts, especially in terms of noise, occur during the construction phase, with biodiversity coming back (sometimes with the creation of new ecosystems through a mechanism called “reef effect”) within a few years.

The “marine protection and restoration” sector is considered here in the broad sense, including both the protection of species and ecosystems as well as area-based initiatives.This fiche sets out the different interactions to be considered between ORE installations and the marine protection and restoration sector, by detailing how such installations can affect surrounding wildlife, how their impacts can be avoided or reduced, and what possible synergistic relationships can be fostered between the two sectors.

Related challenges

Due to the high number of interactions that exist between the ORE sector and the marine protection and conservation sector, the challenges have been categorised into two parts. The first will detail the interactions that represent major challenges. The second category will list the interactions that are either low-risk or for which there is a high level of uncertainty when it comes to their real impact (“secondary challenges”). 

This classification is largely inspired by OES-Environmental and their Report on environmental effects of marine renewable energy development. This classification has also been adopted by the Syndicat des Energies Renouvelables (SER) and the France Renouvelables guide on the effects of offshore wind power on the environment.

It should also be noted that the listed challenges are of particular importance when it comes to fixed-bottom offshore wind, the most dominant and developed ORE technology at present. The significance of each of the following challenges must be reasoned when considering alternative ORE technologies (see the sector’s characteristics”). 

Major challenges

Noise emissions

This challenge is especially important for the most developed and prevalent ORE technology currently, which is fixed-bottom offshore wind. In the case of floating offshore wind, or any other ORE technology (see sector description above) this challenge would likely be less impacting.  
Noise pollution generated by ORE installations and especially OWF is one of the key challenges when it comes to the impact such facilities can have on local ecosystems and wildlife. The construction phase is probably the noisiest phase in the life cycle of a fixed bottom wind farm, as it typically involves the installation of foundations through hydraulic impact piling. Different kind of foundations exist and have different impacts on seabed, as well as noise generation [7][8]. Noise pollution is also emitted during the operating phase, as the movement of the blades can generate noise propagating through the mast and foundations, to which must be added the increase in ambient traffic (maintenance and inspection operations, surrounding traffic, etc). Noise disturbance during the construction and operating phase can lead to changes in the behaviour of a range of marine species, and especially marine mammals and sea turtles because of their high hearing capacity. Local marine fauna can be impacted in several ways, ranging from increased stress levels to behavioural disruption due to the masking of communication signals, animals fleeing the source of noise, or even temporary or permanent hearing damage [9]. Impact piling can generate noise as loud as 235 decibels at the source and can potentially create disturbance avoidance by species up to 25 km from the source of noise [10]. The vast majority of studies report a temporary displacement of individuals close to the site from the start of work as they temporarily migrate to other areas during piling. This is often followed by a return to baseline levels in terms of acoustic activity and population density returns to normal after the piling is finished [11].

Risks of collision and obstacles to the free movement for marine species and flying animals

ORE installations such as OWF can obstruct open space, both in terms of marine and air space. The presence of OWF can represent an obstacle to the free movement of airborne and marine species and can even result in collisions between such species and the installation Collisions represent a risk to biodiversity as they can cause serious injury that can lead to the death of individuals. This applies to marine birds, migratory birds and bats, all at risk of being hit by the rotating blades, but also to marine species (such as marine mammals, sea turtles and large fish) as the risk of underwater collisions is present throughout the life cycle of wind farms. When it comes to the obstruction of free movement, the presence of installations obstacle to the movement of the above-mentioned species which have to adapt their trajectory and modify their behaviour to avoid it. As an example, in the Danish Tuno Knob wind farm, a study of the behaviour of a species of migratory duck showed that the presence of the wind farm forced them to deviate their trajectory [12].

Marine habitats changes

This challenge covers both the destruction of previously existing habitats and the creation of new habitats, both represent potential issues for marine wildlife. 
Firstly, the installation of large ORE installations such as OWF can result in physicaldamage to the sea floor and loss of associated benthic habitats. pose a significant issue for benthic species. The construction of fixed-bottom offshore wind can result in a loss of benthic habitats .
Secondly, the addition of new infrastructure and thus hard substrate in the marine environment may induce a change in environmental conditions by creating new marine habitats. Numerous marine organisms will colonize the new substrate and attract species naturally absent from these areas. Although this could seem like a potentially positive outcome, in reality, this "reef effect" can modify species diversity, distribution and trophic relationships [13].

Electromagnetic emissions

ORE installations such as OWF can emit electromagnetic fields (EMF), which can disrupt the behaviour of certain species that rely on them to orientate or hunt. The emission of artificial EMF can alter their ability to detect and respond to natural electromagnetic signals. Those artificial EMF emissions mainly come from power transmission cables.


Secondary challenges

Artificial light emission

The foundations of and offshore wind turbines themselves are illuminated with lights for navigational safety at sea and in the air. This artificial light can disturb certain species that are more active at night such as squid or bats, but also fish. Artificial light emissions result in individuals being attracted to the new light source and modifying their behaviour to approach it.

Changes in water's physico-chemical properties

This includes several different modifications to the state of the seawater surrounding the OWF, such as increased turbidity, temperature changes, possible chemical pollution and changes in hydrodynamic conditions. 
Turbidity refers to the cloudiness of water. OFW construction operations, such as cable burial, can contribute to the resuspension of sediments. During the operational phase, friction between cables or anchor lines and the seabed can also increase turbidity levels. Increased turbidity in the marine environment reduces water transparency and can affect predator/prey relationships.

During operation of the OWF, power cables can also have a local influence on water temperature. These temperature variations can impact sediment-dwelling species and the egg development of species that bury their eggs in the sediment.

Corrosion protection systems installed on foundations contribute to the release of metals into the environment and are therefore sources of chemical pollution. The increase in maritime traffic linked to maintenance operations also increases the risk of pollution. Chemical pollution impacts all marine species and has consequences for the development and health of individuals.  However, research is unable to rigorously assess the ecological impact of potential chemical pollution associated with ORE, when compared for example to pollution in a marina.

Finally, the physical presence of the OWF can also disrupt the natural flow and movements of water and currents and thus disrupt its hydrodynamic properties. This can affect planktonic communities that naturally drift with the currents. 

Related enablers



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Existing co-existence and multi-use initiatives

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