Another leading environmental charity has lodged an objection to the Viking windfarm proposal in Shetland.
RSPB Scotland said the £800million development in its current form would result in “significant and unacceptable adverse impacts on many bird species”.
It comes after the John Muir Trust warned that the 150 turbines being proposed by Viking Energy would have a serious and hugely damaging impact on the landscape of the islands.
Scientists for RSPB Scotland said nationally important and EU-protected populations of whimbrel, red-throated divers, golden plover and merlin were likely to be displaced or killed by turbines.
They also warned that the effects on peatland habitats during the excavation and construction phases would be so damaging that it could take nearly 50 years for the scheme to start making up for the amount of carbon released into the atmosphere.
RSPB Scotland’s head of conservation policy Lloyd Austin said: “We very much appreciate the consultation that the developers sought with us at the early stages of the design and the effort they have taken to avoid SSSIs (sites of special scientific interest) and other protected areas.
“However, now that we have analysed the full detail of the application, it is clear that a wide range of bird species will be impacted.
“Furthermore, the lack of certainty that there would be any significant net CObenefits undermines the case for development. There is no point in building renewables that potentially emit more carbon due to peatland impacts than they save.”
Mr Austin said the charity would be prepared to review its position if the issues could be satisfactorily resolved, but added that this was likely to require the removal or relocation of turbines and a substantial increase in measures to enhance the biodiversity of the surrounding area.
The proposed Viking windfarm, on Mainland island, is a partnership project between Scottish and Southern Electricity (SSE) and Shetland Charitable Trust.
Backers say the scheme has the potential to generate economic benefits of more than £37million a year for the people of Shetland, in the same way that oil revenues have done for more than 25 years.
Opposition is being led by the campaign group Sustainable Shetland, which favours smaller, community-based renewable projects. More than 3,500 people are said to have signed a petition against the plans.
The final decision on the application will be made by the Scottish Government.