Global warming threat to sea life

Published on Monday 1 June 2009 22:06

MORE than a fifth of the world's whales, dolphins and porpoises are facing potential extinction because of global warming, say Scottish marine scientists.

Five of the six species of porpoises which inhabit the world's oceans are under threat. And one of the cetacean species most at risk from the impact of climate change is the North Sea's population of white-beaked dolphins.

The warning was issued today in the journal Endangered Species Research following a study headed by Dr Colin MacLeod, a research fellow at Aberdeen University. He said the research showed that more whales, dolphins and porpoises than previously thought are at risk from the effects of climate change.

Global warming was likely to affect stretches of sea where almost 90 per cent of the planet's cetaceans are found.

Dr MacLeod said that while some species, such as the common dolphin and the striped dolphin, were likely to benefit from the warming of the seas – increasing their suitable habitat – almost half of all cetacean species would find their areas of suitable habitat shrinking as the temperatures of the world's oceans continue to increase by one degree every decade.

And he claimed: "For 21 per cent of the world's 78 marine cetacean species this decline in habitat availability could be so dramatic that it will greatly increase the risk of extinction."

He said polar species, such as the narwhal and the beluga, were already known to be at risk from climate change. But the study showed for the first time that many species found in more temperate waters were also in danger.

Dr MacLeod said: "In the past, the main concern was for the small number of polar species likely to be affected by a decline in sea ice. However, this new study shows that there are many more species to be worried about.

"Some species found in temperate waters may be at risk not just because of the water temperatures they live in, but also because they only live in shallow waters.

"These species cannot simply respond to increases in sea temperature by moving into cooler neighbouring areas if the waters there are too deep."

The study says the cetacean most at risk in European waters is the white-beaked dolphin found in the North Sea and nearby coastal areas.

In the worst case scenario, according to the research, this could lead to possible extinction if areas of suitable habitat disappear completely.

The Atlantic white-sided dolphin, the northern bottlenose whale and the Sowerby's beaked whale could also disappear from waters around Britain's coast.

And the study claims that five of the world's six species of porpoise – the harbour porpoise, the vaquita, the spectacled porpoise, Dall's porpoise and Burmeister's porpoise – are also under threat.

And even species whose habitat could expand may face other problems. Moving into new areas could see cetaceans mixing with species they normally don't mix with, leading to them being exposed to new parasites and diseases to which they have little or no immunity.

Dr MacLeod said more research was now needed to build up a detailed picture of how species are likely to fare as waters warm, allowing scientists to work out how to save threatened species.