Unicorns of the sea: Dying in the depths

Species are at risk as global warming makes feeding, migration and even breathing critically difficult. By Geoffrey Lean

Narwhals, the "unicorns" of the sea, are in particular danger as whales and dolphins, already depleted by centuries of hunting, are driven towards extinction by global warming, a new report reveals.

Whales that depend on the edges of rapidly retreating polar ice - the narwhal, beluga, bowhead and right whales - are especially vulnerable, as are those living in particularly restricted areas, such as the northern end of the Gulf of California. Those that migrate thousands of miles may be at risk from changes along their route.

The narwhal, the male of which has a left tooth that juts eight feet from its skull, has long fascinated the world. Elizabeth I paid £10,000, more than for a new castle, for a single spiralled tusk. The royal sceptre is made from one.

By some estimates, narwhal numbers are now falling by as much as 10 per cent a year. As the Arctic ice shrinks, their food is also diminishing.

To make things even worse, adds the report by the Whale and Dolphin Conservation Society to be published soon in the nature conservation journal 'Oryx', an anomaly in climate change is leading to more ice in and around Baffin Bay, in northern Canada, the narwhal's main wintering area. This is freezing over the cracks in the ice and patches of open water where they need to surface to breathe.

White beluga whales and the bowhead whale are similarly threatened by the retreating ice, while the right whale is a victim of changes in the North Atlantic Oscillation, which is related to the Pacific weather system that causes El Niño.

But perhaps the most endangered species of all identified by the report is the rare vaquita dolphin, found in the Gulf of California. As the seas warm, marine species usually head for cooler waters, but the vaquita has no escape route as its way north is blocked by land. Mediterranean fin whales and humpback whales in the northern Indian Ocean may be caught in similar marine cul-de-sacs, while white-beaked dolphins living over continental shelves off north-west Scotland also have nowhere to go.

Species in peril: The giants of the deep

Once hunted for their meat and blubber, these whales, while protected from man, are now endangered by the global warming of man's making.

Bowhead whale

Up to 18 metres long - one third of this its head - and 100 tons. A 60cm layer of blubber helps it survive the Arctic waters that are its home. Southern right whale

Southern right whale

Up to 18 metres long and 80 tons. Almost wiped out by 19th-century whalers, it migrates towards Antarctica during the summer months. Beluga whale

Beluga whale

Up to five metres long and 1.5 tons. Known as 'the songstress of the deep', it spends its summers in shallow Arctic bays and winters in pack-ice.