How human noise affects ocean habitats | Kate Stafford

89,391 views ・ 2017-06-05

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In 1956, a documentary by Jacques Cousteau won
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both the Palme d'Or and an Oscar award.
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This film was called, "Le Monde Du Silence,"
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or, "The Silent World."
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The premise of the title was that the underwater world was a quiet world.
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We now know, 60 years later,
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that the underwater world is anything but silent.
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Although the sounds are inaudible above water
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depending on where you are and the time of year,
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the underwater soundscape can be as noisy as any jungle or rainforest.
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Invertebrates like snapping shrimp, fish and marine mammals
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all use sound.
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They use sound to study their habitat,
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to keep in communication with each other,
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to navigate,
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to detect predators and prey.
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They also use sound by listening to know something about their environment.
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Take, for an example, the Arctic.
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It's considered a vast, inhospitable place,
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sometimes described as a desert,
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because it is so cold and so remote
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and ice-covered for much of the year.
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And despite this,
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there is no place on Earth that I would rather be than the Arctic,
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especially as days lengthen and spring comes.
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To me, the Arctic really embodies this disconnect
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between what we see on the surface and what's going on underwater.
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You can look out across the ice -- all white and blue and cold --
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and see nothing.
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But if you could hear underwater,
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the sounds you would hear would at first amaze
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and then delight you.
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And while your eyes are seeing nothing for kilometers but ice,
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your ears are telling you that out there are bowhead and beluga whales,
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walrus and bearded seals.
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The ice, too, makes sounds.
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It screeches and cracks and pops and groans,
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as it collides and rubs when temperature or currents or winds change.
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And under 100 percent sea ice in the dead of winter,
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bowhead whales are singing.
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And you would never expect that,
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because we humans,
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we tend to be very visual animals.
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For most of us, but not all,
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our sense of sight is how we navigate our world.
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For marine mammals that live underwater,
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where chemical cues and light transmit poorly,
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sound is the sense by which they see.
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And sound transmits very well underwater,
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much better than it does in air,
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so signals can be heard over great distances.
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In the Arctic, this is especially important,
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because not only do Arctic marine mammals have to hear each other,
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but they also have to listen for cues in the environment
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that might indicate heavy ice ahead or open water.
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Remember, although they spend most of their lives underwater,
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they are mammals,
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and so they have to surface to breathe.
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So they might listen for thin ice or no ice,
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or listen for echoes off nearby ice.
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Arctic marine mammals live in a rich and varied underwater soundscape.
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In the spring,
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it can be a cacophony of sound.
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(Marine mammal sounds)
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But when the ice is frozen solid,
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and there are no big temperature shifts or current changes,
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the underwater Arctic has some of the lowest ambient noise levels
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of the world's oceans.
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But this is changing.
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This is primarily due to a decrease in seasonal sea ice,
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which is a direct result of human greenhouse gas emissions.
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We are, in effect, with climate change,
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conducting a completely uncontrolled experiment with our planet.
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Over the past 30 years,
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areas of the Arctic have seen decreases in seasonal sea ice
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from anywhere from six weeks to four months.
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This decrease in sea ice is sometimes referred to as an increase
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in the open water season.
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That is the time of year when the Arctic is navigable to vessels.
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And not only is the extent of ice changing,
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but the age and the width of ice is, too.
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Now, you may well have heard
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that a decrease in seasonal sea ice is causing a loss of habitat
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for animals that rely on sea ice,
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such as ice seals, or walrus, or polar bears.
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Decreasing sea ice is also causing increased erosion along coastal villages,
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and changing prey availability for marine birds and mammals.
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Climate change and decreases in sea ice
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are also altering the underwater soundscape of the Arctic.
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What do I mean by soundscape?
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Those of us who eavesdrop on the oceans for a living
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use instruments called hydrophones,
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which are underwater microphones,
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and we record ambient noise --
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the noise all around us.
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And the soundscape describes the different contributors
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to this noise field.
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What we are hearing on our hydrophones
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are the very real sounds of climate change.
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We are hearing these changes from three fronts:
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from the air,
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from the water
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and from land.
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First: air.
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Wind on water creates waves.
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These waves make bubbles;
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the bubbles break,
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and when they do,
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they make noise.
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And this noise is like a hiss or a static in the background.
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In the Arctic, when it's ice-covered,
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most of the noise from wind doesn't make it into the water column,
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because the ice acts as a buffer between the atmosphere and the water.
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This is one of the reasons
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that the Arctic can have very low ambient noise levels.
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But with decreases in seasonal sea ice,
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not only is the Arctic now open to this wave noise,
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but the number of storms and the intensity of storms in the Arctic
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has been increasing.
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All of this is raising noise levels in a previously quiet ocean.
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Second: water.
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With less seasonal sea ice,
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subarctic species are moving north,
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and taking advantage of the new habitat that is created by more open water.
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Now, Arctic whales, like this bowhead,
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they have no dorsal fin,
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because they have evolved to live and swim in ice-covered waters,
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and having something sticking off of your back is not very conducive
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to migrating through ice,
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and may, in fact, be excluding animals from the ice.
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But now, everywhere we've listened,
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we're hearing the sounds of fin whales and humpback whales
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and killer whales,
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further and further north,
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and later and later in the season.
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We are hearing, in essence,
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an invasion of the Arctic by subarctic species.
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And we don't know what this means.
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Will there be competition for food between Arctic and subarctic animals?
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Might these subarctic species introduce diseases or parasites into the Arctic?
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And what are the new sounds that they are producing
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doing to the soundscape underwater?
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And third: land.
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And by land ...
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I mean people.
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More open water means increased human use of the Arctic.
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Just this past summer,
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a massive cruise ship made its way through the Northwest Passage --
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the once-mythical route between Europe and the Pacific.
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Decreases in sea ice have allowed humans to occupy the Arctic more often.
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It has allowed increases in oil and gas exploration and extraction,
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the potential for commercial shipping,
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as well as increased tourism.
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And we now know that ship noise increases levels of stress hormones in whales
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and can disrupt feeding behavior.
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Air guns, which produce loud, low-frequency "whoomps"
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every 10 to 20 seconds,
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changed the swimming and vocal behavior of whales.
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And all of these sound sources are decreasing the acoustic space
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over which Arctic marine mammals can communicate.
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Now, Arctic marine mammals are used to very high levels of noise
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at certain times of the year.
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But this is primarily from other animals or from sea ice,
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and these are the sounds with which they've evolved,
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and these are sounds that are vital to their very survival.
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These new sounds are loud and they're alien.
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They might impact the environment in ways that we think we understand,
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but also in ways that we don't.
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Remember, sound is the most important sense for these animals.
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And not only is the physical habitat of the Arctic changing rapidly,
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but the acoustic habitat is, too.
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It's as if we've plucked these animals up from the quiet countryside
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and dropped them into a big city in the middle of rush hour.
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And they can't escape it.
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So what can we do now?
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We can't decrease wind speeds
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or keep subarctic animals from migrating north,
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but we can work on local solutions
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to reducing human-caused underwater noise.
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One of these solutions is to slow down ships
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that traverse the Arctic,
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because a slower ship is a quieter ship.
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We can restrict access in seasons and regions
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that are important for mating or feeding or migrating.
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We can get smarter about quieting ships
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and find better ways to explore the ocean bottom.
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And the good news is,
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there are people working on this right now.
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But ultimately,
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we humans have to do the hard work
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of reversing or at the very least decelerating
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human-caused atmospheric changes.
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So, let's return to this idea of a silent world underwater.
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It's entirely possible
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that many of the whales swimming in the Arctic today,
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especially long-lived species like the bowhead whale
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that the Inuits say can live two human lives --
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it's possible that these whales were alive in 1956,
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when Jacques Cousteau made his film.
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And in retrospect,
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considering all the noise we are creating in the oceans today,
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perhaps it really was "The Silent World."
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Thank you.
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(Applause)
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