A synthesis of effects and impacts of offshore wind farms upon wildlife: from seabed communities to fish, marine mammals and birds

This third volume of 'Wildlife and Wind Farms: conflicts and solutions' compiles all the known and potential effects of offshore wind farms on the different trophic levels of marine fauna, from benthic communities to birds, including fish and marine mammals. It presents a summary of the effects and impacts highlighted by the 18 specialists who participated in the writing of this work. Most of the information comes from feedback from offshore wind farms in northwest Europe: in the operational phase, the impacts on underwater life stem mainly from modifications to the coastal maritime currents caused in particular by wake effects which may cause variations in the water level over large areas and modify biological productivity. During the construction phase, the noise caused by piles can cause the displacement of fish and marine mammals, and even certain birds; the impact can be temporary but also permanent. After construction, the foundations of the turbines as well as the rock-fill intended to protect them from scouring are quickly colonized, often by anemones, amphipods and molds; this reef effect is generally considered to be positive as it leads to the aggregation of fish, especially large predators such as cods, thus attracting marine mammals and birds such as cormorants. However, the risk that wind farms could be used to support the development of invasive species cannot be excluded. The disturbance caused by wind turbines during the exploitation phase affects birds differently depending on the species. Few cases of collisions have been observed, in particular because it remains technically difficult to record such events. Some studies show that individuals have a variable response to the risk of collision, and that this reaction can also vary according to reproductive status. The massive collisions of migratory birds and bats are causing considerable concern, although the evidence remains limited at this time. The cumulative effects of several offshore wind farms have barely started to be addressed, so the precautionary principle should apply and the turbine sites should be carefully selected in order to avoid conflicts