Safeguarding aerial migrants need not jeopardize wind energy production

With global ambitions to decarbonize the energy system, the installed capacity of wind turbines will continue to increase dramatically worldwide. This raises concerns about environmental impacts of wind energy infrastructure and operations, particularly for collision of aerial wildlife.

Using a network of weather surveillance radars, we quantified numbers, timing and spatial extent of nightly and annual large-scale bird movements over Western Europe. We also mapped onshore windfarms and calculated potential energy production using wind speeds and distribution data. Integrating 3D bird movement patterns, turbine traits and energy production, we estimated the number of birds that are potentially at risk of collision because they fly in proximity to wind turbines and at heights of rotating blades.

We found that an average of 794 birds flew through the rotor-swept area of a single wind turbine per year, yielding an estimated total of 208 million birds potentially at risk of colliding over the year across the study area. Yet, there was considerable spatial and temporal variation in the number of birds at risk, with peaks over the two seasons of intense migration. When accounting for the dynamic orientation of wind turbines in response to main wind direction, this number was reduced to 134 million birds and further to 114 million when considering cut-in and cut-out wind speeds during which blades cease rotating. Potential energy production varied geographically but was reatively evenly spread over the year, with a total of 718 petajoules (or nearly 200,000 kilowatt hours).

To demonstrate the potential for designing measures to mitigate risk to aerial biodiversity, we derive several curtailment scenarios and compare costs and benefits for energy production and conserving biodiversity and show that surprisingly efficient trade-offs are possible. Thus, with our approach we can derive solutions for addressing multiple, seemingly contrasting challenges - the need for a transition to net-zero and to halt biodiversity loss.