More on windfarms and their effects on biodiversity

Wind power plants possibly represent the icon of the energy transition, due to the majesty of their windmills and their ability to produce large amounts of electricity. Wind power plants are currently made up of groups of tens to hundreds of wind turbines that, on land, exceed 120m in height with blades of up to 50m and powers of 2-3 MW (and experiments are already being carried out with 5 MW generators). Offshore wind power plants are even larger, with wind turbines of up to 9 MW and total capacities of 500-1000 MW, in the same range as nuclear or traditional fossil fuel plants.

The main described effects of this type of facility on biodiversity are the mortality of birds and bats, sometimes endangered species, that collide with the moving blades. It is known that mortality is highly variable between wind farms, between wind turbines in the same park, and between astronomical stations; and that can affect between one and dozens of individuals in each wind turbine per year. The most impacted birds are usually soaring birds (e.g., raptors) that take advantage of the air currents on the slopes, coinciding with the wind turbines located on mountain crests, or migratory species of birds and bats that cross the parks in their seasonal movements. Relevant mortalities have also been found of species that live in the vicinity of wind farms, and that can sometimes suffer pronounced population declines, and of all kinds of small birds.

In fact, it is disputed whether the estimated proportions of dead birds of different sizes directly reflect the bias of the unlikely encounter of small dead (and potentially broken into pieces) birds scattered over an area of several hectares around each wind turbine. And the same can be said about the complexity of finding bat carcasses, due to their size and lack of resistant structures such as feathers.

The direct effects of wind farms on habitats are less relevant than in other types of electricity generation plants due to the lower effective occupation of the land, but the construction work, the preparation and maintenance of access roads, and the operation of wind turbines produce cascade effects on ecosystems whose existence is appreciated, but whose relevance is poorly understood. Thus, for example, it is known that opportunistic predators (e.g., foxes) use park access roads in their daily movements, and that, during their journeys scavenging the remains of dead birds, they find and prey on nests and individuals young or adult birds and land mammals. The noise and disturbance generated by the windmills also alter the composition and functioning of the animal communities, situations such as the generation of low-intensity predation areas where predators avoid proximity to wind farms have been described.

In the case of offshore wind farms, knowledge is even more fragmented due to the difficulty of observation, having described both the deviation of migratory routes of some birds, as well as the use of the wind farm structures as resting points by others. In addition, offshore wind farms have traditionally been located in low-lying areas near the coast, but floating systems are currently being developed that will allow their generalization in deep waters further from the coast.