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Coral Comeback: Corals Under Threat

5 minutes

(Describer) Under a round logo of a wave, title: Ocean Today.

(Describer) Pedestrians and traffic move in fast-motion.

(female narrator) We live a big life on a small planet. The human population has grown from five to over seven billion in one generation, and consumption has escalated too. Building homes, factories, and roads often leads to a better quality of life, but it increases pollution in the air and water.

(Describer) Grey water gushes from a pipe.

Greenhouse gases, like carbon dioxide, have raised the global temperature. Our collective impact is so large, it is dramatically changing the chemistry of the ocean.

(Describer) Waves roll onto a beach.

Activities such as burning fossil fuels release carbon dioxide, or CO2, into the air, but a large part is absorbed by the ocean. CO2 in the water causes the ocean to become more acidic, and a more acidic ocean means it's harder for creatures like reef-building corals and shellfish to create and maintain their calcium carbonate skeletons and shells, and that weakens them.

(Describer) Bleached coral is white.

Locally, trash, boats anchoring on the reef, destructive fishing practices, and the wrong sunscreen worn by swimmers can also sicken corals. These local issues compound the global threat of a warming and acidifying ocean.

(Describer) The Earth is viewed from space.

The world's largest reef-- the Great Barrier Reef of Australia-- can be seen from space. It is home to more than 1500 species of fish and estimated to be 500,000 years old, one of the wonders of the natural world.

(Describer) A turtle sits on it while many fish swim around.

But in 2016, most of the Great Barrier Reef's corals bleached, and almost 25% died from an astonishingly long period of intensely high water temperatures driven by global warming.

(Describer) An animated map shows eight weeks of coral exposed to heat stress, meaning significant death.

None of the central and northern sections of the reef were spared from the heat stress that causes bleaching. The northern third was hit hardest, and two-thirds of its corals died. Tragically, mass die-offs are again happening on the reef for an unprecedented second year in a row in 2017. Even worse, it was not an isolated incident. All of the world's corals are in danger.

(Describer) Doctor Ruth Gates:

(woman) We have lost, already, approximately 50% of the world's reefs. This has occurred, really, in the last three decades-- so fast, when we're talking about an organism that has been on the planet and been in symbiosis with its microalgae for over 50 million years. And the incidence of bleaching is increasing in frequency and intensity as the planet warms.

(narrator) It's not every year that water temperatures stay high enough long enough for corals to bleach. In fact, extreme high temperatures used to come in cycles, often driven by climate events like El Niño. Due to climate change, the higher temperatures are becoming more frequent, more intense, and more widespread. The underwater heat waves that have devastated the corals on the Great Barrier Reef are part of the third global coral bleaching event. This one has now lasted three years-- by far the longest, most widespread, and most damaging yet. And it continues even now. It's feared that corals could now face bleaching so often that whole reefs, and even species, will be lost forever.

(Describer) Bleached reefs are shown in different parts of the world.

NOAA's Coral Reef Watch program and others use satellites to monitor the heat stress that can cause coral bleaching and use climate models to predict where bleaching may occur on the world's tropical coral reefs in the next few months. But what can we do to reduce the risks? Can corals make a comeback? Watch our next video in this series to find out.

(Describer) Titles: Narrator: Lori Berman. oceantoday.noaa.gov. Logos are shown for the Smithsonian and NOAA. Accessibility provided by the US Department of Education.

Accessibility provided by the U.S. Department of Education.

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Societal change and growth is impacting the ocean ecosystem. One of these consequences is the rapid decline and death of coral reefs. Part of the "Coral Comeback" series.

Media Details

Runtime: 5 minutes

Coral Comeback
Episode 1
2 minutes
Grade Level: 7 - 12
Coral Comeback
Episode 2
4 minutes
Grade Level: 7 - 12
Coral Comeback
Episode 3
4 minutes
Grade Level: 7 - 12
Coral Comeback
Episode 4
5 minutes
Grade Level: 7 - 12
Coral Comeback
Episode 5
6 minutes
Grade Level: 7 - 12
Coral Comeback
Episode 6
6 minutes
Grade Level: 7 - 12
Coral Comeback
Episode 7
4 minutes
Grade Level: 7 - 12
Coral Comeback
Episode 8
3 minutes
Grade Level: 7 - 12
Coral Comeback
Episode 9
3 minutes
Grade Level: 7 - 12