LONDON — THE people of the Shetland Islands in northern Scotland are still trying to measure how much damage was done when the tanker Braer ran aground and spilled 84,500 tons of crude oil in coastal waters Jan. 5.
A picture is emerging of a disaster that superficially appeared to have been less serious than first thought but is likely to produce unwelcome effects on human and animal life in the future.
Scientists are using a computer model in an attempt to discover whether oil that has sunk beneath the surface is being swept along by ocean currents into fishing grounds far beyond the Shetlands.
Local councillors speak of a near-miraculous cleansing of the beaches since the accident, thanks mainly to waves up to 50 feet high breaking up the oil and washing it out to the deep ocean.
But fishermen and farmers, citing scientists' findings, are talking of a long-term threat to their industries.
When the spill occurred there was alarm and deep anxiety among the Shetlanders as environmentalists warned of a polluted coastline for years to come and birds and seals fell victim to the belching crude.
Oil was whipped up by gale-force winds that carried it inland, forcing farmers to move their sheep. Islanders complained of health problems linked to the oil and to dispersants dropped from aircraft near the wreck.
Local councillors also spoke of a threat to the Shetlands' appeal as a remote tourist area. The complaints were fanned by a series of national newspaper advertisements from Greenpeace and other environmental groups, forecasting massive destruction of North Sea wildlife and threats to human health.
In fact, only about 1,500 dead birds were recovered in the five weeks after the tanker ran aground, compared with 36,000 after the Exxon Valdez spill off Alaska in 1989.
Martin Huebeck, field coordinator at the Shetlands Wildlife Response Center, estimates that the dead birds found represent about one-fifth of the total that perished.
Fears for the Shetlands' 1,000 otters turned out to be almost groundless. Only four were found dead - one of them was run over by a television crew. Eleven seals were found dead.
Other seals, covered in oil, were hospitalized at a sanctuary in northern Shetland. Since then there have been reports of seals and seal pups swimming ashore with symptoms of oil poisoning.
Mr. Huebeck says the fact that the Braer was carrying light crude was an important reason for the rapid dispersal of the tanker's oil from Shetland beaches.
"It broke up more easily than heavy crude would have done," Huebeck says. He concedes, however, that little is known about the longer-term effects of the spill on marine creatures in the area and the way pollution may affect the fish and crabs normally exported to mainland Britain.
The Natural Environment Research Council, which is tracking the Braer's oil using a computer model, has found that significant quantities of the oil may remain beneath the surface, some of it on the seabed. It might stay there and be ingested by deep sea fish, or eventually rise to the surface, said Roger Proctor, one of the scientists working on the project. Environmental campaigners refuse to accept that the threat of oil entering the food chain can be discounted, or that wild creatures in the area are
out of danger.
As a precaution against oil from the Braer entering the human food chain the government has declared a fishing exclusion zone around southern Shetland.
Graham Topping, a marine scientist, said background levels of hydrocarbons on the edge of the zone were 10 times higher than normal. At its center, levels were hundreds of times higher.
Damage has been caused to some of the 16 salmon farms within the exclusion zone. Last year, salmon farming earned 33 million pounds ($47 million) for Shetlanders.
Fish farmers in the area say they will demand compensation for salmon stocks declared to have been poisoned.
The government has already earmarked $1.42 million for payments to the fish farmers, but there is certain to be pressure to increase the sum if scientists confirm that serious harm has been done to the salmon farms.