An ocean of noise: how sonic pollution is hurting marine life
We were whaling with cameras, joining a flotilla of a dozen other tourist boats from harbours all around the Salish Sea. It was one of my first trips to the area, in August 2001. The fuzz and beep of ship radios stitched a net over the water, a blurry facsimile of the sonic connections of the whales themselves. Every skipper heard the voices of the others, relayed by electromagnetic waves. The quarry could not escape. “Whales guaranteed” shouted the billboards on shore.
We motored on, weaving around island headlands. A sighting off the south-west shore of San Juan Island. Through binoculars: a dorsal fin scythed the water, then dipped. Another, with a spray of mist as the animal exhaled. Then, no sign. But the whales’ location was easy to spot. A dozen boats clustered, most slowly motoring west, away from the shore. We powered closer, slowing the engine until we were travelling without raising a wake and took our place on the outer edge of the gaggle of yachts and cruisers.
A sheet of marble skated just under the water’s surface. Oily smooth. A spill of black ink sheeting under the hazed bottle glass of the water’s surface. Praaf! Surfacing 15 metres ahead of the boat, the exhalation was plosive and rough.
The pod of about 10 animals came to the surface. Part of the L pod of orcas, our captain said, one of three pods that form the “southern residents” in the waters of the Salish Sea between Seattle and Vancouver, often seen hunting salmon around the San Juan Islands. Others – “transients” that ply coastal waters and “offshores” that feed mostly in the Pacific – also visit regularly. The L pod continued west, heading toward the Haro Strait. Our engines purred as the U-shaped arc of boats tracked the pod, leaving open water ahead of the whales.
We dropped a hydrophone over the boat’s gunwale, its cord feeding a small speaker in a plastic casing. Whale sounds! And engine noise, lots of engine noise. Clicks, like taps on a metal can, came in squalls. These sounds are the whales’ echolocating search beams. The whales use the echoes not only to see through the murky water, but to understand how soft, taut, fast or tremulous matter is around them.
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Mixed with the staccato of the whales’ clicks were whistles and high squeaks, sounds that undulate, dart, inflect up and spiral down. These whistles are the sounds of whale conviviality, given most often when the animals are socialising at close range. When the pod is more widely spaced during searches for food, the whales whistle less and communicate with bursts of shorter sound pulses. These sonic bonds not only connect the members of each pod, but distinguish the pod from others.
Today, ocean waters are a tumult of engine noise, sonar and seismic blasts. Sediments from human activities on land cloud the water. Industrial chemicals befuddle the sense of smell of aquatic animals. We are severing the sensory links that gave the world its animal diversity. Whales cannot hear the echolocating pulses that locate their prey, breeding fish cannot find one another amid the noise and turbidity, and the social connections among crustaceans are weakened as their chemical messages and sonic thrums are lost in a haze of human pollution.
Here off the coast of San Juan Island, the whales’ voices were like fine silk stitched into a thick denim of propeller and motor sound, clicks and whistles sometimes audible but often disappearing into the tight weave of engines. The dozen boats gave off throbs, whirs and shudders as they tracked the whales, combustion engines swaddling the whales in an inescapable, constricting wrap.
In the distance, I could see a container ship and an oil tanker headed north through the Haro Strait, likely bound for Vancouver, the largest port in the region – two of the more than 7,000 large vessels that, combined, make more than 12,000 transits through the strait every year. These range from bulk carriers to container ships to tankers, many of which are 200 or 300 metres long. Large vessels also ply the waters west of the Haro Strait, headed to ports and refineries in and around Seattle and Tacoma. Each one of these vessels makes sound audible underwater from tens, sometimes hundreds, of miles.
Unlike small pleasure boats that are usually moored at sundown, these large vessels make noise all night and day, and are often most active and loudest at night. The largest container ships blast at about 190 underwater decibels or more, the equivalent on land of a thunderclap or the takeoff of a jet.
The southern resident whale community whose life centres on these waters cannot bear the noise. Their population is in decline, likely headed to extinction unless the world gets more hospitable. In the 1990s, the community numbered in the 90s. Now they’ve dropped to the low 70s, losing one or two more animals every year without raising new calves. In 2005, they were listed under the US Endangered Species Act. No single factor is responsible, but the interaction of shipping sounds, dwindling food supply and chemical pollution is, for now, closing the door on their future.
These whales are the falcons of the ocean, rocketing down 100 metres or more in pursuit of their nimble and speedy prey, the chinook salmon. Sound frequencies of boat noise overlap with the clicks that the animals use to echolocate and find their prey. Noise raises a fog, blinding the hunters. If a whale is within 200 metres of a container ship or 100 metres of a smaller boat with an outboard engine, its echolocation range is reduced by 95%.
In air, we hear only a low groan from passing vessels. The sound is mostly transmitted down, below the waves, and the aerial portion is quickly dissipated. Under the surface, the sonic violence of powered boats travels fast and far through the pulse and heave of water molecules. These movements flow directly into aquatic living beings. Sound in air mostly bounces off terrestrial animals, reflected back by the uncooperative border of air to skin. Our middle-ear bones and eardrum are specifically designed to overcome this barrier, gathering aerial sound and delivering it to the aquatic medium of the inner ear. Sound, for us, is focused mostly on a few organs in our heads. But aquatic animals are immersed in sound. Sound flows almost unimpeded from watery surrounds to watery innards. “Hearing” is a full-body experience.
For most whales, and for many fish and invertebrate animals, eyes are only occasionally useful. In the abyssal depths, the animals swim in ink. Along coasts, the water is so turbid that animals see, at most, a body length ahead. Sound reveals the shapes, energies, boundaries and other inhabitants of the sea. Sound is also a communicative bond. In the ocean, as is true in the rainforest where dense foliage occludes vision, sound connects you to unseen mates, kin and rivals, and it alerts you to nearby prey and predators.
If salmon were abundant, all this noise might not be a problem. But the chinook salmon that compose most of the whales’ diet here are in crisis. Dams, urbanisation, agriculture and logging have cut off or degraded most of the freshwater rivers and streams in which the fish spawn and live out their first months. Chinook salmon numbers in this region have declined by 60% since the 1980s, and possibly more than 90% since the early 20th century. Under current conditions, models forecast, at best, a fragile southern resident population. Any additional stress will send them to extinction.
Facebook Twitter A humpback whale and her calf. Photograph: lindsay_imagery/Getty
Since 2017, the Port of Vancouver has enacted a voluntary slowdown of shipping traffic headed through the Haro Strait. For 30 nautical miles, large vessels slow, adding about 20 minutes to the ships’ voyages. Ship noise increases with speed, and so dialling back the throttle lessens the cacophony in a place where the southern resident whales often feed. More than 80% of vessels have complied with the project.
Yet traffic increases yearly in the region, more than eliminating the quiet gained by shaving some noise from each passing ship. In 2018, crude oil exports from Vancouver increased dramatically, mostly destined for China and South Korea. In 2019, the Canadian government approved an expansion that would nearly triple the capacity of the pipeline that supplies much of the oil from the tar sands region of Alberta. Vancouver’s port is seeking approval for a vast new container terminal. In 2021, the nonprofit Friends of the San Juans catalogued more than 20 other proposals to build new or expanded shipping terminals for containers, oil, liquefied gas, grain, potash, cruise ships, coal and car carriers in the region. If approved, these would increase traffic by more than 25%.
Seven hundred kilometres north of Vancouver, the fjords that lead to the port of Kitimat are home to several species of whales living in relatively unpolluted and quiet waters. Under construction there is a liquefied natural gas terminal that is slated to add 700 new large-vessel transits, a more than thirteenfold increase, not counting the powerful tugs that would accompany the tankers as they navigate rocky fjords.
The US navy also plans expanded exercises in the region, including the use of explosives and loud sonar. By its own estimates, across the Pacific north-west coast, navy “acoustic and explosive” exercises, including those in the waters favoured by the southern residents, will kill or injure nearly 3,000 marine mammals and disrupt the feeding, breeding, movements and nursing of 1.75 million more.
The whales in and around the San Juan Islands and the Haro Strait live in a constriction point for much of the trade that passes between Asia and North America, supplemented with some shipping from the Middle East and Europe. The vast majority of the consumer goods and bulk commodities that move between the continents do so on ships. I look around at my material possessions. Whales, either in the Haro Strait or perhaps off the coast of Los Angeles, heard the arrival of every item made in a country on the Pacific rim: laptop, silverware, watering can, furniture and car.
Whales living along the Atlantic coast were immersed in the sounds of deliveries from Europe and north Africa: office chairs, books, wine and olive oil. Having lived most of my life inland, many hours’ drive from the sea, I have seldom seen or heard whales. But the whales hear me. They are immersed in the sounds of my purchases from over the horizon every day of their lives.
The converging shipping lanes around major seaports are focal points for a noise problem that extends across the oceans. In the 1950s, about 30,000 merchant vessels plied the world’s oceans. Now about 100,000 do, many of them with much larger engines. Tonnage of cargo has increased tenfold.
Ambient noise on the Pacific coast of North America has increased by about 10 decibels since the 1960s, when the measurements started. By some estimates, noise levels in the world’s oceans have doubled every decade since the mid-20th century. The noise is worse around the major shipping lanes that connect major ports across the northern Pacific and Atlantic, for example, but because sound propagates readily in water, the rumble reaches for hundreds of kilometres. When a large ocean-bound ship crosses the continental shelf, its sound shoots to the deep ocean floor, several miles down, then bounces up off the sediment and into the deep sound channel. This channel carries the noise thousands of miles. Across much of the world, it is now impossible to measure the background levels of ocean sound without engine traffic.
Facebook Twitter An orca. Photograph: sethakan/Getty Images
Near to shore, small-boat traffic adds another, higher-pitched, layer of sound, as I discovered on the deck of the whale-watching boat. The number of recreational boats in the US has increased by 1% a year for the past three decades. In coastal Australia, the annual rate of increase in the number of small boats has recently reached up to 3%. The sound from these smaller vessels does not travel as far, but for many animals living in coastal waters it is the dominant sound source. At close range, sonar – sounds emitted from shipboard devices to detect the sea floor, schools of fish and enemy submarines – can add to these higher-pitched noises.
Into this global mire of noise comes the loudest human noise of all – the percussive beat of our industrialised search for energy. Prospectors blast sound into the ocean, seeking oil and gas buried under ocean sediments. Ships drag arrays of air guns that shoot bubbles of pressurised 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. These waves spread in all directions. Those that go down penetrate the sea floor, then bounce back when they hit reflective surfaces. By measuring these reflections from the ship, geologists can build a 3D image of the varied layers of mud, sand, rock and oil tens or even hundreds of miles under the seabed. 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 2,500 miles away.
The blast of an air gun emerges from a metre-long, missile-shaped canister towed behind the survey ship. 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. These batteries go off about once every 10 to 20 seconds. The ship tracks methodically back and forth through the ocean, like a lawnmower, in surveys that can run continuously for months, covering tens of thousands of square miles. 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 US, Canada, northern Europe and the west coast of Africa.
Stand on an ocean shore, and you will not hear the sound of seismic surveys. Take a ship into deep water and, even there, water’s reflective boundary and our air-adapted ears shield us. Analogy fails, too. 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 miles necessary to escape. The pile-driver is coupled, minute by minute, to every nerve ending and cell, suffusing them with the violence of explosions.
Ocean creatures, especially near to shore or along busy trade routes, now live in a din previously unknown except near underwater volcanoes or during an earthquake. Wind-stirred waves, breaking ice, earthquakes, the motion of bubbles in water columns, and the sounds of whales and snapping shrimp are the sounds to which marine life is adapted. 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 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.
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.
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For now, these changes are mostly experimental, hypothetical or enacted in small corners of the oceans. Regulation of marine noise happens piecemeal by country, with no binding international standards or goals. The noise in the oceans continues to worsen. A 2016 estimate of global shipping noise projected a near doubling by 2030. A review in 2013 found that expenditures on seismic surveys were increasing at nearly 20% a year, more than $10bn annually, capping two decades of rapid growth. The Covid-19 pandemic briefly slowed this rise, but demand for more surveys will probably surge as oil prices rise. The US military plans to start broadcasting continuous noise into all ocean basins to guide underwater vehicles.
We possess the technology and economic mechanisms needed to reduce our noise. But we lack sensory and imaginative connection to the problem, and thus the will to act. Today a single whale can sometimes be heard from across an entire ocean basin. Imagine millions of these animals giving voice. When some of the whales alive today were young, every water molecule in the oceans continually thrummed with the sound of whales. Vociferous fish formerly sang by the billions on their breeding grounds and added their sounds to the whales’ calls. The ocean world pulsed, shimmered and seethed with song. These sounds connected animals into fruitful and creative networks. Given a chance, this could return.
• This article was amended on 13 April 2022. The report by Friends of the San Juans (not San Juan) was published in 2021, not 2019.
This is an edited extract from Sounds Wild and Broken: Sonic Marvels, Evolution’s Creativity and the Crisis of Sensory Extinction, published by Faber on 21 April and available at guardianbookshop.co.uk
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