A humpback whale (Megaptera novaeangliae), one of the many cetaceans relying on sound across vast distances.
Credit: Louis Herman/NOAA
The Royal Australian Navy, for one, isn't taking chances. When it discovered the Perth Canyon - the nearest deepwater exercise area to the submarine base on Garden Island in Western Australia - was also a favoured haunt of pygmy blue whales, the navy asked a team of local biologists to investigate. Their research found that whale visits to the canyon were seasonal, coinciding with a flush of krill from February to May every year. The navy tactfully decided to yield right of way to the whales, moving its exercises.
French biologist Michel André, who chairs the European Cetacean Society, considers sound can kill sea life in various ways. André investigated the rising carnage in the Canaries as fast ferries crossing between the main islands 25 times a day collided with sperm whales - killing them and, sometimes, even people. His study of the dead whale's ears led him to conclude the whole population had been partially deafened by noise pollution.
"The more noise we put in the ocean, the more we affect the way the animals that live there communicate and orientate," André said. "And this means that we are compromising their survival. We're compromising the way they look for their food. We're compromising the way they breed.
"Nowadays there is no region anywhere that's unaffected by noise pollution. Due to its low-frequency components, a sound source may propagate for thousands of miles. The control of these sources constitutes a scientific challenge and involves an important responsibility for society and governments."
Amid the rumble of claim and counter-claim one fact stands out: there is no law - international or otherwise - that controls noise pollution at sea. So far, it has mainly been the strength of public and scientific opinion that has induced oil explorers, ship owners and navies to investigate the possible side effects of their noisy activities on marine life.
Some governments are erring on the side of caution. Australia's Department of the Environment and Heritage classifies acoustic disturbance as an 'intermediate threat' to whale populations: "Any human activities which produce loud and persistent sounds under water are likely to interfere seriously with the acoustic perception and communication of any cetaceans in the vicinity, and have the potential to induce significant levels of stress ... incessant or repeated acoustic disturbance could cause abandonment of important habitats such as narrow migration paths and calving and nursery sites".
Meanwhile, the World Conservation Union has urged governments to apply the precautionary principle to marine noise pollution, to investigate mass strandings that may be associated with intense manmade noise, and to encourage the development of less noisy alternative technologies. They also say powerful noise sources should be controlled until their effects are better understood, should be avoided in sensitive areas, and should be subject to restriction under marine and coastal management guidelines.
"Regulating sound sources can be difficult, but one has to start somewhere," says Sylvia Earle. "Every breath we take is dependent on the ocean. Unless we really understand how that vast system works and take better care of it, it isn't just the ocean that's in jeopardy; it's our whole future that's at stake."
Julian Cribb is a science writer and communications consultant in Canberra.
