Are wind farms and biodiversity on a collision course?

Renewable energy production is growing rapidly as part of global efforts to combat climate change. However, one of the major forms of renewable energy, wind farms, can have negative impacts on biodiversity through mortality associated with turbines, according to new research from the British Trust for Ornithology (BTO).

In order to help reduce the potential for conflict between solutions for a greener future and a healthy biodiversity, the results also identify which species are most vulnerable and where they are concentrated.

Lead author, Dr Chris Thaxter of the BTO, said: “It is vital to consider the impacts of wind farms on populations of both bats and birds, especially for migrants and wide-ranging species. Considering where to place [turbines] – for example, avoiding migratory flyways – could greatly reduce the risk of collisions. Future research should prioritise work in developing countries where wind power may soon become an alternative to fossil fuel as these countries try to meet climate mitigation goals, as well as off-shore wind farms. This will surely help to find the delicate balance between a greener future and healthy biodiversity.”

Although known about from studies in Europe and North America, there is little information from other regions where wind farms are expanding rapidly. The new study, published in Proceedings of The Royal Society B, identifies for the first time the potential vulnerability of bird and bat species around the world to collisions with wind turbines and suggests how such collisions may be avoided.

To achieve this, the BTO led a review of published papers documenting collision rates with onshore wind turbines. In order to extrapolate these observations to less-well studied species, rates of collision were modelled in relation to factors including birds’ migratory behaviour and ecology, and wind turbine height and capacity.

Collision rates of the 769 bird species tested were affected by habitat, migratory strategy and dispersal distance. Birds using artificial habitats such as farmland had a higher risk of collision with turbines, potentially because more wind farms are placed these habitats than in others and because such landscapes tend to be more open. It was also found that migrant birds and bats that dispersed further had a higher risk of collision.

Birds of prey were the most vulnerable avian species, which is problematic as many such species are slow to reproduce and have populations that are highly sensitive to reductions in survival rates. Collision rates in general were predicted to be higher for bats than for birds, with a number of North American species such as Hoary and Eastern Red Bats particularly vulnerable.

Importantly, the results suggest that building fewer large turbines may actually reduce the risk of collision for birds for a given amount of energy generated, although turbines with a capacity over 1.25 MW were associated with higher collision rates for bats.

Dr James Pearce-Higgins, Director of Science of the BTO and author of the paper said: “Although these results may seem to infer that wind farms are bad for biodiversity and should be opposed, this study actually provides an important way forward to facilitate renewable energy to combat climate change while minimising the impacts on vulnerable species. By identifying which species are most vulnerable, and where those species are found, these results can inform strategic spatial planning to indicate where wind farms may be least damaging, and to identify the priority species for impact assessment by individual developments. The use of appropriately sized turbines may also minimise collision risk.”