The Shetland Islands are one of Europe's most important breeding sites for cliff-nesting birds and the winter home for one of the rarest migrants, the great northern diver. Extensive oil pollution would also devastate the relatively large colony of about 700 otters, conservationists said.
Salmon farming, the second largest industry after oil, could be badly damaged if large amounts of chemical dispersants, which are toxic to fish, are used. The Shetlands account for more than a quarter of British production of farmed salmon, worth pounds 35m.
Mike Matthew, a conservationist at the Scottish Natural Heritage, said the bird colony most at risk is the wintering flock of eider duck in the Pool of Virkie, an inlet about three miles up the east coast from the stricken tanker.
He said that at this time of year particularly large numbers of eider ducks, probably 1,000 or more, are resident. About 10 per cent of the UK's population of eider duck - about 7,500 birds - live in the Shetlands.
Oil has a devastating effect on seabirds: oily feathers cause death from cold and poisoning as birds preen themselves. 'If birds become thoroughly oiled they may just survive if caught, but they can be difficult to catch if they are still able to move,' Mr Matthew said.
The Shetlands are home to curlew, shag, redshank, godwits, mallard, widgeon, teal, the long-tailed duck, puffins and razorbills. The Wildfowl and Wetlands Trust at Slimbridge, Gloucestershire, said the islands are probably the most important UK site for wintering sea ducks.
Sand dunes in the Bay of Quendale, near where the ship is aground, are designated a site of special scientific interest. Fitful Head, about three miles up the west coast, is an important national beauty spot.
Sumburgh Head, a rocky promontory at the southern tip of Mainland, is an important summer nesting site for cliff-dwelling birds, such as black guillemots. Ruth Briggs, Scottish Heritage's area manager for the northern isles, said the bad weather would have driven most birds to more sheltered areas. 'If the oil comes out of the tanker in large amounts and spreads over a wide area quickly, the birds will be hard presssed to avoid it.'
There are contingency plans to get contaminated birds to treatment areas outside the Shetlands, she said. 'But if there is a lot of oil, there is little we can do.'
Mike Harris, an ornithologist at the Institute of Terrestrial Ecology at Banchory, near Aberdeen, said: 'Even a relatively small oil spill in a confined area can have quite a dramatic effect. It can take between five and ten years for birdlife to recover.'
The worst possible outcome is for the tanker to sink and leak oil for months, he said. 'There would be a catastrophic effect if the oil hangs around until the summer breeding season begins.'
More than 700 otters live in the Shetlands and the spill could have an enormous impact on their numbers, said Hans Kruuk, a sea mammal specialist at the Institute of Terrestial Ecology, adding: 'The Shetlands' otter population is one of the best in Europe. It would be a tragedy.' Other sea mammals that could be affected are seals and porpoises.Reuse content