Twenty-six Government-designated sites of special scientific interest (SSSIs) on the coastline of west Wales have been hit by slicks, according to the Countryside Council for Wales - the Government's wildlife conservation arm in the principality. They include mudflats, rocky and sandy shores and cliffs, designated because they are particularly rich in plant and animal species or have rare flora and fauna.
The sites cover the intertidal zone (between the low- and high-tide marks) - exactly where the oil has been deposited. They stretch from Wales's only undersea nature reserve around the island of Skomer in the west to the beaches and dunes of Pendine and Laugharne Sands in the east.
''Until this happened, we could not imagine a single event which would cause so much damage,'' said Malcolm Smith, science and policy director with the Countryside Council for Wales. ''We thought there would eventually be a serious tanker accident, but we didn't imagine it would affect such a length of coastline.'' At least 120 miles has been oiled - 12 per cent of the principality's entire coastline - and most of that is within the Pembrokeshire Coastal National Park.
This oiling is patchy, with extensive lengths having so far escaped the heavy slicking that leaves thick black and brown deposits blanketing rocks, sand and pebbles. Yet dozens of miles of coastline have been smeared in this way; there almost all life has been wiped out in the intertidal zone. Since much of it lies at cliff bases and is impossible to reach from land, it will never be cleaned by man.
Extra-high tides and storms can take this oil back out to sea, from where it can be driven back onto nearby shorelines. Thus the huge oil spill - some 70,000 tonnes - could continue to cause pollution for months to come, slicking beaches that have been cleaned or managed to escape damage.
When the Prince of Wales visited the area on Thursday, Dr Robin Crump, a marine biologist who runs the Orielton Field Studies Centre near Milford Haven, impressed him with his account of the scale of the ecological damage.
As Prince Charles toured West Angle Bay, where the oil has destroyed one of just seven British populations of the brooding cushion starfish, he pointed to yellow lichens on rocks at the high-tide mark. They had been obliterated.
''Each of those has taken decades to grow,'' he said. ''The oil came in on the high spring tides and got right up into this golden band. Here we have some of the richest intertidal communities in Europe.''
More than 3,000 oiled birds have now been rescued, and over 2,000 found dead.