Offshore wind farms threaten world’s largest northern gannet colony
Northern gannets around the UK are at much greater risk from wind turbine blades than previously thought, according to new scientific research.
Several wind farms are due to be built in the next five years at locations within 50 kilometres of Bass Rock, the world’s largest northern gannet colony, located in the Firth of Forth off the east coast of Scotland.
The northern gannet is amber listed according to a UK national assessment of Birds of Conservation Concern. This new study, published in the Journal of Applied Ecology, highlights the urgent need for further research to inform wind turbine specifications and locations.
Northern gannets were previously thought to fly well below the permitted minimum blade clearance height of 22 metres above sea level. This new study suggests that gannets fly below this height only when flying between breeding and feeding grounds. While hunting and diving for prey, these large seabirds with a wingspan of almost two metres, were found to reach heights of 27 metres, placing them at risk of collision with rotating blades.
The study findings suggest that the collision risk has been seriously underestimated and up to 12 times more gannets could be killed than previously thought.
Previous collision risk estimates were based on flight height data from radar limited to a range of six kilometres, and subjective ship-based observations. Estimates in this new study are based on more reliable data from Global Position System (GPS) loggers and barometric pressure loggers. Movements of gannets rearing chicks on Bass Rock were tracked from mid-June to mid-August over a three year period.
Led by Professor Keith Hamer, of Leeds University’s School of Biology, researchers from Leeds, Glasgow and Exeter Universities found that gannets flew at a median height of 12 m when travelling between the colony and foraging sites, but flew at a median height of 27 m when actively foraging.
The research team estimate a potential mortality rate of 1500 breeding gannets from the Bass Rock colony between April and September each year from blade collision at the two planned wind farm sites.
A large increase in offshore wind turbine capacity is anticipated within the next decade, especially in shallow waters in Europe.
The research team recommends raising the minimum permitted clearance height of turbine blades from 22 m to 30 m above sea level at sites with high collision risk for foraging gannets. Further research data from GPS and barometric pressure loggers is also suggested to enable a proper assessment of the risk of offshore wind farms to gannets and other vulnerable bird populations.
Full article at Nature in Mind
Image credit: Gannets at Bass Rock by Robert Orr on Flickr (CC BY-ND 2.0)
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