Are Offshore Wind Farms a Friend or Foe of Marine Life?

Renewable energy sources are undoubtedly booming around the world as an increasing number of countries seek greener and cleaner ways to fuel their growing demand for energy. Developing countries, in particular, are under immense pressure to overhaul their outdated energy systems as quickly as possible into modern networks which limit greenhouse emissions and therefore reduce their impact on the planet. Yet there are many debates about which types of renewable energy we should be using. Solar panels may work brilliantly in cities where they can be installed across thousands of rooftops but in the countryside, solar panels often take up large patches of land and prohibit them from being used for anything else. Many people support green energy options but don’t actually want turbines scattered across their favourite countryside vista or making a constant noise just outside their backyard. It seems one of the solutions to satisfy almost everyone is to take wind turbines and place them out at sea where there are no neighbours and also where the wind is much more reliable. Out there amongst the waves, wind farms are happily out of sight for many but this means they are out of our minds too and do we really know what impact these coastal constructions have on our marine life?

Globally, offshore wind capacity is growing at around 15-30% annually and on the whole, this is fantastic news for our planet! By using renewable energy sources, we lower the level of carbon dioxide which is pumped into our atmosphere and absorbed by our oceans. Did you know that our oceans absorb around 25% of all the carbon dioxide that is released from the burning of fossil fuels? The increased level of carbon entering the ocean is causing sea temperatures to rise worldwide whilst the saltwater is also becoming more acidic, both changes which have devastating impacts on marine ecosystems and their inhabitants. Yet in the short term, offshore wind farms can cause a range of ecological issues which are often overlooked and easily so, as most of the impacts are hidden beneath the waves.

As soon as the construction of an offshore wind farm commences, so does some of the physical damage they cause. Many types of wind turbine require foundations which are placed deep into the seabed and the drilling of the ocean floor can destroy any marine habitats in the local area whilst also stirring up large amounts of sediment. This causes enormous clouds of sand and silt to hang in the water column until eventually settling down again. When the sediment comes back down to rest however, it can often smother corals, sponges and anemones which makes feeding, and simply surviving, a lot more challenging. Swirls of sediment can also block out sunlight meaning plants and algae on the seafloor struggle to photosynthesis and feed themselves.

Yet noise pollution from the construction process is by far the largest threat to our marine creatures. Pile driving is measured to give out about 200 decibels of noise, however studies have shown that harbour porpoises only need 90 decibels of noise before they start avoiding an area. In fact, harbour porpoises have been found to take a 20 kilometre detour just to avoid loud drilling noises in the ocean. If disturbance is frequent, this can mean marine mammals, such as porpoises, dolphins, whales and seals, might be forced to avoid certain feeding or breeding grounds which are a crucial part of their natural life. For species like dolphins which use echolocation, noise pollution is especially harmful as it can prevent them being able to communicate with others in their pod, hunt for food effectively and navigate around the ocean. Unfortunately, the natural sounds of whale songs and dolphin’s clicks, whistles and squeaks just cannot compete with large drills and pile drivers. Fish too are impacted by a noisy undersea environment with both cod and herring able to detect pile driving up to an astonishing 80 kilometres away! Even the normal operation of the turbine produces 120 decibels of noise and over a long period of time, this can cause hearing loss as well as prolonged stress which can lead to weakened immune responses. 

One last threat is that once turbines are installed, their bases and hard surfaces provide a great place for invasive species to make a home and repopulate. In the past, invasive species would not have been able to survive in some parts of the ocean as the seafloor was too barren, exposed and lacking food, yet underwater constructions are now providing new homes for certain species. One study in Holland found that over three years, nine new invasive species could be found in an offshore wind farm including far-from-home Pacific oysters. Not all invasive species have the ability to cause major disruption but some can form new predators, tuck into local prey and spread additional diseases which massively impact native sea creatures.

It is not only invasive species which can make our wind farms into a home however. The solid structures of both the foundations and the turbine itself provide excellent artificial reefs for new corals to attach to and build a new reef, forming the biggest bonus to these blue technologies. With a maze of underwater objects added to the ocean, there is an increased surface area for creatures to latch on to and inhabit which means there is a higher potential for colonisation. The cold metal bases of turbines can soon be decorated in mussels, algae, anemones, starfish sponges and even oysters, all of which then attract larger species such as fish and seabirds, creating a mini hub of biodiversity. In fact, these areas could be very similar to the marine life which can be found close to shore hugging onto the legs of old piers. 

Offshore wind farms can also help reduce some of the other pressures placed on our oceans as select farms ban fishing trawlers from the area whilst in many cases, fishermen voluntarily avoid trawling in the area as they fear their nets will get entangled on the foundations. This means that overfishing is unlikely to occur within the boundaries of wind farms and combined with the fact that lots of algae and small crustaceans make the foundations their home, means that these areas could become a safe space for commercially targeted fish. 

So far it seems that the overall impact of offshore wind farms on our marine environment is a little uncertain, with both good and bad impacts to consider. However, there are several things we can do to mitigate the harmful effects and boost the beneficial aspects to make this modern technology even more planet friendly. In the initial construction phase, some countries have made it a necessity to have spotters out in the area which look for pods of whales or dolphins travelling towards the site. If a pod is spotted, pile driving is halted to allow them time to communicate effectively and move away as a group. Similarly, even starting drilling slowly and building up to louder noises can give marine creatures time to move out of the area. Ingenious bubble curtains can even be placed around drilling sites. These machines create a constant stream of bubbles which actually act as a sound insulator and have been found to reduce avoidance behaviour from porpoises by up to 90%. All these measures have a surprisingly high level of support from national governments as many marine mammals, particularly in Europe, are protected by law. 

Whilst species may be scared away during the building phase, sometimes they do return to the area and the likelihood of a wind farm having a high level of biodiversity can be increased by carefully considering their design. Foundations and turbines already form great artificial reef structures but small tweaks to the design could allow them to house even more marine invertebrates which all play essential roles with the food chain. The level of biodiversity in the area however, will crucially depend on how far away it is from other feeding and breeding grounds. If fish, for example, must travel a vast distance between their established feeding ground and the growing new feeding spot in the wind farm, they often won’t bother making the journey. Therefore, by placing small artificial structures on the seabed in the surrounding area, stepping stones can be built across the seafloor which allow species to travel between various patches of ocean without having to cross vast distances which lack both food and protection from predators. This would require engineers to work closely with conservationists and ocean scientists but it could allow degraded areas of seabed to be restored by creating a habitable space for marine creatures. This could be particularly important for our vulnerable and rapidly declining invertebrate populations which are often forgotten about in marine conservation. With various specialists working together, the final location of wind farms could also be more effectively decided as scientists can make useful contributions as to whether they will interrupt historical whale and seabird migration pathways. By avoiding popular routes, we can reduce the risk of noise pollution and physical harm.

So it seems that offshore wind does indeed have the potential to give our marine ecosystems a helping hand but only if we include a wide range of stakeholders in the planning process. This will allow a conservation-based approach to be considered and allow the chance of achieving a win-win scenario, where both green energy and marine conservation are boosted, much more likely. After all, the transition to clean and sustainable society must not further damage the ecosystems it was designed to protect.

By Neve McCracken-Heywood