Gannets are at much higher risk from offshore wind farms being built on the UK’s coastline than previously thought, a new study has warned.
Offshore wind farms could claim the lives of up to 1,500 birds each year and pose a greater threat to protected populations according to a new study by teams at the universities of Leeds, Exeter and Glasgow.
Researchers have discovered that the gannets, which breed in the UK between April and September each year, generally flew well below the minimum height of 22 metres above sea level swept by the blades of offshore wind turbines.
While this is the case when the birds are simply “commuting” between their nest sites and distant feeding grounds, the new study revealed the birds fly five metres above the minimum blade height when actively searching and diving for prey.
Dr Ian Cleasby, of the University of Exeter and lead author of the study, said: “Previous data had seriously underestimated the number of birds potentially at risk of colliding with turbine blades. There’s a lot of uncertainty over how many birds would actually be killed this way, but our predictions – if realised in the field – are high enough to cause concern over the potential long-term effects on population size.
“Our predictions suggest extra care be taken when designing and assessing new wind farms to reduce their impact on gannets.”
The study also shows that the birds’ feeding grounds overlap extensively with planned wind farm sites in the Firth of Forth, heightening their risk of colliding with turbine blades.
Professor Keith Hamer, of the School of Biology at Leeds, oversaw the study, published today in the Journal of Applied Ecology.
His research group, together with colleagues from Exeter and Glasgow, based their work at Bass Rock, the world’s largest colony of gannets with some 70,000 breeding pairs, in the Firth of Forth near Edinburgh.
Bass Rock is less than 50km from several planned wind farm sites.
He said: “Our study highlights the shortfalls in current methods widely used to assess potential collision risks from offshore wind farms, and we recommend much greater use of loggers carried by birds to complement existing data from radar studies or observers at sea.”
The researchers estimate that up to 12 times more gannets could be killed by turbines than current figures suggest, although they stress that the figure is based on calculations using current typical turbine sizes, which could be different to those actually installed, and that there is great uncertainty over actual turbine avoidance rates.
Previously data on gannet flight heights were obtained by one of two methods: trained surveyors on boats estimating heights by eye, or radar, which usually has a limited range of about 6km and is costly.
Co-author Dr Ewan Wakefield, of the University of Glasgow, said: “For the first time we’ve been able to track birds accurately in three dimensions as they fly from their nests through potential wind farm sites.
“Unfortunately, it seems that many gannets could fly at just the wrong heights in just the wrong places.
“Increasing the distance between the tips of the spinning turbine blades and the sea would give gannets more headroom – so we strongly urge that the current minimum permitted clearance turbine height be raised from 22m to 30m above sea level.”
Using miniaturised light-weight GPS loggers and barometric pressure loggers, temporarily taped the birds’ tails, the researchers tracked the flights of gannets in three-dimensions as they flew out from the Bass Rock, searching for fish.
They then used the data in a predictive model which suggested that, based on available estimates of the proportion of birds that would be likely to avoid the turbine blades, about 1,500 breeding birds could be killed each year at the two planned wind farms nearest to the Bass Rock.
One US study published in the Wildlife Society Bulletin in 2013 found that wind turbines kill 573,000 birds (including 83,000 raptor fatilities) and 880,000 bats each year in America.
The UK researchers concluded that more sophisticated methods of assessing risk should be adopted urgently.
Hannah Smith, Policy Officer for Scottish Renewables, said: “It’s important to put this research into context. It focuses on developing a new method using a tiny sample of less than one percent of the total gannet population that can be found at the Bass Rock.
“Offshore wind farm developers in Scotland spend up to three years collecting detailed data on bird populations which is then scrutinised by various nature conservation bodies as part of their planning application.
“These assessments are then put before the appropriate Scottish Government specialists to ensure the work is scientifically robust as well as meeting all required national and international environmental legislation. This is a rigorous process designed to ensure that developments do not have an adverse impact upon our environment.”
Smith added: “I am sure that the Scottish Government will look at this latest piece of research, along with all the other work by academic researchers, renewable energy developers and environmental agencies and assess if it is relevant to how they consider any future applications for offshore wind projects.”
The Royal Society for the Protection of Birds said it scrutinises hundreds of windfarm applications every year to determine their likely impact on wildlife.
The RSPB said: “We ultimately object to about 6% of those we engage with, because they threaten bird populations. Where developers are willing to adapt plans to reduce impacts to acceptable levels we withdraw our objections, in other cases we robustly oppose them.”
The government expects offshore wind power could supply between eight and 10% of the UK’s annual electricity supply by 2020. It currently supplies about 4%, according to the latest official figures.
The study was funded by the Natural Environment Research Council and the Department of Energy & Climate Change (DECC).
A further, more extensive tagging study to improve understanding of gannet flight heights and behaviour and led by Prof. Hamer has been funded by DECC in 2015.