An Approximation Of Loudness And Relentlessness

The number of recreational boats in the United States increased by 1 percent per year for the last three decades. In coastal Australia, the annual rate of increase in the number of small boats has recently reached up to 3 percent. The sound from these smaller vessels does not travel as far, but is the dominant sound source for many animals living in coastal waters. Some naval sonar is loud enough to permanently damage the hearing of marine animals at close range. Into this global mire of noise comes the loudest human noise of all, the percussive beat of our industrialized search for buried sunlight. Like whales seeking their prey with echolocating clicks, human prospectors blast sound into the ocean, seeking oil and gas buried under ocean sediments. Ships drag arrays of air guns that shoot bubbles of pressurized air into the water, a replacement for the dynamite that was formerly tossed overboard for the same purpose. As the bubbles expand and collapse, they punch sound waves into the water, an industrial version of the fizz of snapping shrimp claws I heard on Saint Catherines Island. Like a whale guided by the reflective ping of a Chinook salmon, oil and gas companies use sound to find their quarry. But unlike the click of a whale, these seismic surveys can be heard up to four thousand kilometers away. The sound can be as loud as 260 underwater decibels, six to seven orders of magnitude more intense than the loudest ship. The guns are typically deployed in arrays of up to four dozen.

Time After Time

These batteries go off about once every ten to twenty seconds. The ship tracks methodically back and forth through the ocean, like a lawn mower, in surveys that can run continuously for months, covering tens of thousands of square kilometers. When the surveys encompass the open ocean, beyond the edge of the continental shelf, as they frequently do in this era of expanding numbers of deepwater oil rigs, the sound flows into the deepwater channel and, like shipping noise, spreads across ocean basins. In some years in the North Atlantic, dozens of surveys run at once and a single hydrophone can pick up the relentless sound of seismic surveys off the coasts of Brazil, the United States, Canada, parts of northern Europe, and the west coast of Africa. Seismic surveys are widely used wherever unctuous treasure might be buried under the sea, including Australia, the North Sea, Southeast Asia, the Middle East, and South Africa. Underwater seismic pounding feeds every one of us who use oil and gas. Yet we have no shred of sensory experience of the consequences of our hunger for these fossils. Stand on an ocean shore, and you will not hear the sound of seismic surveys. A pile driver in your house, running without stop for months? That gives an approximation of the loudness and relentlessness, but we can walk away from the house, and even when we stand next to the machine, the assault mostly affects only our ears. For aquatic creatures, sound is sight, touch, proprioception, and hearing. They cannot leave the water. Few can swim the hundreds of kilometers necessary to escape.

Aren't You Glad You're You?

The pile driver is coupled, minute by minute, to every nerve ending and cell, suffusing them for months on end with the violence of explosions. Ocean life, especially near to shore or along busy trade routes, now lives in a din previously unknown except near underwater volcanoes or during an earthquake. But the blast of air guns, the needling and stab of sonar, and the throb of engines are new and, in most places, far louder than just a few decades ago. The worst places in the ocean are now intolerable for much ocean life. Whales flee areas in which seismic testing is underway. A study off the southwest coast of Ireland found nearly a 90 percent decrease in sightings of baleen whales and a halving of sightings of toothed whales during active seismic surveys compared with control surveys with no blasting. Air guns also decimate the base of the ocean food web, the plankton and larvae of marine invertebrate animals. The sound waves from the blast may have shaken the animals to death and, for the survivors of the initial shock, so ripped up the sensory hairs that cover the animals’ bodies that the plankton soon died, stripped of any ability to hear or feel their world. The sensory systems of larger invertebrate animals like lobsters can also be permanently destroyed by exposure to seismic surveys. Sound bleeds them to death from within. Under assault from sonar, some whales come into the surf, try to hide behind rocks, or beach themselves in a bid to escape the torturous whine. These strandings and frenzied bids to escape the water bring the whales into the human visual realm, a rare sign accessible to the human senses of the crisis below the waves.

Live Another Day

Even when sound is not immediately lethal, it exacts a toll. A recent review of more than 150 scientific studies of whales, dolphins, seals, and other marine mammals found that noise reduces feeding, cuts off echolocation, increases time spent traveling, decreases rest, changes the rhythms of diving, and drains energy reserves. Some species respond to ship noise by increasing the loudness and rate of their calls, others go silent. Whales are social animals, living in continuous acoustic contact with their families and cultural groups. Whaling greatly reduced the complexity and abundance of these societies. Noise further degrades and severs social bonds. In highly social terrestrial animals, we know that reducing or eliminating connection to others injures, and in extreme cases kills, individuals. Noise also changes both the behavior and physiology of fish. In a noisy environment, they often become agitated, darting about as if a predator were close. But when a real predator shows up, they seem unable to defend themselves, not startling and speeding away as they should. For fish that use sounds during their breeding displays, noise has variable effects. Some species ramp up their calling, perhaps to shout over the background, but others go quiet. For many, noise either blocks or greatly reduces the range over which they can be heard.