The deafening sound of the seas

By Alex Kirby
BBC News Online environment correspondent

Bowhead whales: Mothers and calves may lose touch

The world's oceans are now so saturated with noise that whales and other marine mammals are dying, biologists say.

The UK's Whale and Dolphin Conservation Society is launching a campaign, Oceans of Noise, to tackle what it says is the increasing problem of noise pollution.

It says key sources of undersea noise are the search for oil and gas, and the use of low-frequency military sonars.

The WDCS is proposing an action plan to regulate submarine noise pollution, and says a worldwide treaty may be needed.

Long-distance effects

It says there is evidence that noise is causing hearing loss in cetaceans (whales, dolphins and porpoises), injuring them and causing them to strand themselves, and is sometimes killing them.

It also believes excessive noise is seriously interfering with cetaceans' ability to communicate with each other.

The WDCS says the frequency ranges of some noise sources of human origin may be blotting out other, biologically important sounds, preventing mothers and calves from staying in touch and masking sound cues for predators and their prey.

It says: "Flight, avoidance or other changes in behaviour have been observed in cetaceans from tens to hundreds of kilometres from the noise sources.

"It has even been suggested that the abilities of the great whales to communicate with each other across entire ocean basins has now been reduced by orders of magnitude."

The International Whaling Commission said in July there was "compelling evidence" that entire populations of marine mammals were at potential risk from increasingly intense man-made underwater noise.

Its scientific committee said low-frequency ambient marine noise levels had increased in the northern hemisphere by two orders of magnitude over the last 60 years.

The WDCS says one problem is the expansion of oil and gas exploration into the deep seas and the resulting growth in seismic testing to find fossil fuel deposits.

Out of sight

Shipping is another cause of concern. The society says: "Large vessels are typically loud vessels and the increase in traffic has actually fundamentally changed the noise profile of the world's oceans."

And the use of powerful sonar systems by some of the world's navies, it says, is raising noise levels still further.

The WDCS action plan includes a proposal for an international treaty to regulate marine noise pollution, and for an independent body to undertake research.

Mark Simmonds of the WDCS told BBC News Online: "It's a problem that doesn't have much noticeable effect on us, unlike chemical pollution, and we can't see it either.

"And that means it's hard for us to realise the problem exists, let alone its extent."

Bowhead image courtesy and copyright of the US National Oceanic and Atmospheric Administration.