Today’s oceans are a tumult of engine roar, artificial sonar and seismic blasts that make it impossible for marine creatures to hunt or communicate. It is high time we stop it, reports the Guardian.
Quieter oceans are within reach
The noise in the ocean today is infernal, but unlike chemical pollution that lingers sometimes for centuries, or plastics that will persist for millennia, sound pollution can be shut off in an instant. Silence from humans is unlikely, since the energy and materials that supply our bodies and economies move largely by ship. Most of our oil, gas and food travels among continents by sea. There is little chance, therefore, that the noise will cease entirely. But quieter oceans are within reach.
It is possible to build almost silent ships. Navies have been doing so for decades. Fisheries researchers seeking to measure fish abundance and behaviours do so from vessels with engines, gears and propellers engineered to reduce noise and thus not alarm fish. The hush from these ships comes at the cost of efficiency and speed. Yet even for large commercial vessels, noise can be greatly reduced through careful design. Regular propeller repair and polishing reduce the formation of cavitation bubbles that are the main source of noise.
Slowing the vessel, even by 10% or 20%, also cuts noise, sometimes by up to half. Many of these changes save fuel, giving a direct benefit to the ship operators, although not always enough to offset the costs of expensive reengineering. More than half of the noise in the oceans comes from a minority – between one-10th and one-sixth – of the vessels, often older and less efficient craft. Quieting this clamorous minority could significantly reduce noise.
But volume of traffic needs to be reduced: quieter ships might lead to more ship collisions if whales cannot hear approaching danger. For millions of years whales have safely travelled and rested at the water’s surface. Now blows from hulls and slashes from propellers are significant risks for whales in ocean shipping lanes and around busy ports.
Harmful effects of sonar can be reduced
The most harmful effects of sonar can also be reduced, at least for large marine mammals, by locating navy exercises away from known feeding and calving grounds, tracking whales and shutting down war games when they are close, gradually ramping up sound levels so that animals have time to escape, and reducing longterm exposure by not repeatedly subjecting the same animals to high-amplitude sonar. As with shipping noise, reducing the overall number of ships conducting exercises would have the most significant effect.
Even seismic surveys can be hushed. Machines that send low-frequency vibrations down into the water column yield excellent maps of buried geology while making less noise than air guns. This “vibroseis” technology is regularly used on land but has yet to be widely adopted in the ocean. Marine vibroseis produces sounds that overlap with animal senses and communicative signals, but does so over smaller areas and in a narrower frequency range.
Did you subscribe to our daily newsletter?
It’s Free! Click here to Subscribe!
Source: The Guardian
