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  • In 1956, a documentary by Jacques Cousteau won

  • both the Palme d'Or and an Oscar award.

  • This film was called, "Le Monde Du Silence,"

  • or, "The Silent World."

  • The premise of the title was that the underwater world was a quiet world.

  • We now know, 60 years later,

  • that the underwater world is anything but silent.

  • Although the sounds are inaudible above water

  • depending on where you are and the time of year,

  • the underwater soundscape can be as noisy as any jungle or rainforest.

  • Invertebrates like snapping shrimp, fish and marine mammals

  • all use sound.

  • They use sound to study their habitat,

  • to keep in communication with each other,

  • to navigate,

  • to detect predators and prey.

  • They also use sound by listening to know something about their environment.

  • Take, for an example, the Arctic.

  • It's considered a vast, inhospitable place,

  • sometimes described as a desert,

  • because it is so cold and so remote

  • and ice-covered for much of the year.

  • And despite this,

  • there is no place on Earth that I would rather be than the Arctic,

  • especially as days lengthen and spring comes.

  • To me, the Arctic really embodies this disconnect

  • between what we see on the surface and what's going on underwater.

  • You can look out across the ice -- all white and blue and cold --

  • and see nothing.

  • But if you could hear underwater,

  • the sounds you would hear would at first amaze

  • and then delight you.

  • And while your eyes are seeing nothing for kilometers but ice,

  • your ears are telling you that out there are bowhead and beluga whales,

  • walrus and bearded seals.

  • The ice, too, makes sounds.

  • It screeches and cracks and pops and groans,

  • as it collides and rubs when temperature or currents or winds change.

  • And under 100 percent sea ice in the dead of winter,

  • bowhead whales are singing.

  • And you would never expect that,

  • because we humans,

  • we tend to be very visual animals.

  • For most of us, but not all,

  • our sense of sight is how we navigate our world.

  • For marine mammals that live underwater,

  • where chemical cues and light transmit poorly,

  • sound is the sense by which they see.

  • And sound transmits very well underwater,

  • much better than it does in air,

  • so signals can be heard over great distances.

  • In the Arctic, this is especially important,

  • because not only do Arctic marine mammals have to hear each other,

  • but they also have to listen for cues in the environment

  • that might indicate heavy ice ahead or open water.

  • Remember, although they spend most of their lives underwater,

  • they are mammals,

  • and so they have to surface to breathe.

  • So they might listen for thin ice or no ice,

  • or listen for echoes off nearby ice.

  • Arctic marine mammals live in a rich and varied underwater soundscape.

  • In the spring,

  • it can be a cacophony of sound.

  • (Marine mammal sounds)

  • But when the ice is frozen solid,

  • and there are no big temperature shifts or current changes,

  • the underwater Arctic has some of the lowest ambient noise levels

  • of the world's oceans.

  • But this is changing.

  • This is primarily due to a decrease in seasonal sea ice,

  • which is a direct result of human greenhouse gas emissions.

  • We are, in effect, with climate change,

  • conducting a completely uncontrolled experiment with our planet.

  • Over the past 30 years,

  • areas of the Arctic have seen decreases in seasonal sea ice

  • from anywhere from six weeks to four months.

  • This decrease in sea ice is sometimes referred to as an increase

  • in the open water season.

  • That is the time of year when the Arctic is navigable to vessels.

  • And not only is the extent of ice changing,

  • but the age and the width of ice is, too.

  • Now, you may well have heard

  • that a decrease in seasonal sea ice is causing a loss of habitat

  • for animals that rely on sea ice,

  • such as ice seals, or walrus, or polar bears.

  • Decreasing sea ice is also causing increased erosion along coastal villages,

  • and changing prey availability for marine birds and mammals.

  • Climate change and decreases in sea ice

  • are also altering the underwater soundscape of the Arctic.

  • What do I mean by soundscape?

  • Those of us who eavesdrop on the oceans for a living

  • use instruments called hydrophones,

  • which are underwater microphones,

  • and we record ambient noise --

  • the noise all around us.

  • And the soundscape describes the different contributors

  • to this noise field.

  • What we are hearing on our hydrophones

  • are the very real sounds of climate change.

  • We are hearing these changes from three fronts:

  • from the air,

  • from the water

  • and from land.

  • First: air.

  • Wind on water creates waves.

  • These waves make bubbles;

  • the bubbles break,

  • and when they do,

  • they make noise.

  • And this noise is like a hiss or a static in the background.

  • In the Arctic, when it's ice-covered,

  • most of the noise from wind doesn't make it into the water column,

  • because the ice acts as a buffer between the atmosphere and the water.

  • This is one of the reasons

  • that the Arctic can have very low ambient noise levels.

  • But with decreases in seasonal sea ice,

  • not only is the Arctic now open to this wave noise,

  • but the number of storms and the intensity of storms in the Arctic

  • has been increasing.

  • All of this is raising noise levels in a previously quiet ocean.

  • Second: water.

  • With less seasonal sea ice,

  • subarctic species are moving north,

  • and taking advantage of the new habitat that is created by more open water.

  • Now, Arctic whales, like this bowhead,

  • they have no dorsal fin,

  • because they have evolved to live and swim in ice-covered waters,

  • and having something sticking off of your back is not very conducive

  • to migrating through ice,

  • and may, in fact, be excluding animals from the ice.

  • But now, everywhere we've listened,

  • we're hearing the sounds of fin whales and humpback whales

  • and killer whales,

  • further and further north,

  • and later and later in the season.

  • We are hearing, in essence,

  • an invasion of the Arctic by subarctic species.

  • And we don't know what this means.

  • Will there be competition for food between Arctic and subarctic animals?

  • Might these subarctic species introduce diseases or parasites into the Arctic?

  • And what are the new sounds that they are producing

  • doing to the soundscape underwater?

  • And third: land.

  • And by land ...

  • I mean people.

  • More open water means increased human use of the Arctic.

  • Just this past summer,

  • a massive cruise ship made its way through the Northwest Passage --

  • the once-mythical route between Europe and the Pacific.

  • Decreases in sea ice have allowed humans to occupy the Arctic more often.

  • It has allowed increases in oil and gas exploration and extraction,

  • the potential for commercial shipping,

  • as well as increased tourism.

  • And we now know that ship noise increases levels of stress hormones in whales

  • and can disrupt feeding behavior.

  • Air guns, which produce loud, low-frequency "whoomps"

  • every 10 to 20 seconds,

  • changed the swimming and vocal behavior of whales.

  • And all of these sound sources are decreasing the acoustic space

  • over which Arctic marine mammals can communicate.

  • Now, Arctic marine mammals are used to very high levels of noise

  • at certain times of the year.

  • But this is primarily from other animals or from sea ice,

  • and these are the sounds with which they've evolved,

  • and these are sounds that are vital to their very survival.

  • These new sounds are loud and they're alien.

  • They might impact the environment in ways that we think we understand,

  • but also in ways that we don't.

  • Remember, sound is the most important sense for these animals.

  • And not only is the physical habitat of the Arctic changing rapidly,

  • but the acoustic habitat is, too.

  • It's as if we've plucked these animals up from the quiet countryside

  • and dropped them into a big city in the middle of rush hour.

  • And they can't escape it.

  • So what can we do now?

  • We can't decrease wind speeds

  • or keep subarctic animals from migrating north,

  • but we can work on local solutions

  • to reducing human-caused underwater noise.

  • One of these solutions is to slow down ships

  • that traverse the Arctic,

  • because a slower ship is a quieter ship.

  • We can restrict access in seasons and regions

  • that are important for mating or feeding or migrating.

  • We can get smarter about quieting ships

  • and find better ways to explore the ocean bottom.

  • And the good news is,

  • there are people working on this right now.

  • But ultimately,

  • we humans have to do the hard work

  • of reversing or at the very least decelerating

  • human-caused atmospheric changes.

  • So, let's return to this idea of a silent world underwater.

  • It's entirely possible

  • that many of the whales swimming in the Arctic today,

  • especially long-lived species like the bowhead whale

  • that the Inuits say can live two human lives --

  • it's possible that these whales were alive in 1956,

  • when Jacques Cousteau made his film.

  • And in retrospect,

  • considering all the noise we are creating in the oceans today,

  • perhaps it really was "The Silent World."

  • Thank you.

  • (Applause)

In 1956, a documentary by Jacques Cousteau won

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【TED】Kate Stafford: How human noise affects ocean habitats (How human noise affects ocean habitats | Kate Stafford)

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    Zenn posted on 2017/07/28
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