Guest Host: Indira Lakshmanan

Fish swimming through the coral on Australia's Great Barrier Reef in 2014. Scientists say large sections of the Great Barrier Reef are now permanently dead because of climate change.

Fish swimming through the coral on Australia's Great Barrier Reef in 2014. Scientists say large sections of the Great Barrier Reef are now permanently dead because of climate change.

They’re home to about one quarter of all known species of marine life and provide food and livelihoods for hundreds of millions of people. But the world’s coral reefs are dying fast. Scientists warn that only ten percent of all reefs will survive past 2050 because of climate change, and researchers are racing to protect the least-vulnerable reefs before they disappear.


  • C. Mark Eakin Coordinator, the National Oceanic and Atmospheric Administration's Coral Reef Watch program
  • Nancy Knowlton Sant Chair for Marine Science, the Smithsonian National Museum of Natural History; author of "Citizens of the Sea."
  • Richard Vevers Founder, The Ocean Agency; director, the 50 Reefs conservation initiative.
  • Ku'ulei Rodgers Associate researcher, Hawaii Institute of Marine Biology, University of Hawaii

Watch Coral Bleaching Happen Before Your Eyes

This video, taken by scientists in a laboratory at Queensland University of Technology in Brisbane, Australia, captures a coral ejecting its resident population of algae. The behavior helps corals survive warmer water in the short term, but extended periods of bleaching can be lethal to corals and the ecosystems they support. (Video courtesy Brett Lewis, QUT)

March 2017 Was Second-Warmest March On Record, Says NASA

Show Highlights

On parts of Australia’s Great Barrier Reef dying:

Richard Vevers: “We’ve actually been to the reef on multiple occasions—looking at the reef before, during and after these bleaching events. The most shocking expedition for me was one last year when we went to the far northern part of the Great Barrier Reef, which is my favorite reef system in the world. We jumped in the water there and it was dead for as far as the eye could see. It wasn’t just looking at this dead reef that had transformed from a beautiful reef just a few months earlier, where we’d seen the corals literally get covered in algae—they looked like they’d been dead for years. It was to the point of which I got out of the water, and realized I smelled like dying animals. People often forget the coral reefs are animals, and this is a mass mortality event on a really epic scale. We’ve focused this year on some of the new bleachings because there’s been a second wave of bleaching this year, which is really unprecedented for the Great Barrier Reef. This year we’ve been focusing on really getting imagery of the bleaching itself, which is really happening around the main tourist areas.”

What are corals?

Nancy Knowlton: “Corals are very simple animals. Imagine a tin can with one end open and a ring of tentacles around that open end. They feed with their tentacles and these symbiotic plant cells, which are so sensitive to temperature, photosynthesize and provide food as well. So they’re glued to the bottom. They have a skeleton and when they are babies they land on a good place to settle and glue themselves to the body. The only way they can really migrate is through the next generation of babies that they produce which drift in the water for a while before settling down again.”

On the loss of half the coral reefs globally in the last 30 years: 

Mark Eakin: “Some of the big losses that started in the Caribbean at the beginning was a major disease outbreak that went through and affected the branch and corals that were such an important part of those systems. At the same time, we started seeing the problem of global coral bleaching…These were all driven by high temperatures where global warming is increasing the temperature of the water and it’s forcing the corals to have to eject these algae into the water. It leaves them starving, it leaves the sick, injured and in many cases, they are dying.”

“Pollution is a big problem on a local basis as is overfishing and habitat destruction, these local things are hugely important. Acidification is important on a global scale, but it’s secondary to the temperatures.”

On climate change as the biggest threat:

Richard Vevers: “One of the biggest facts about climate change, that people don’t often realize, is 93% of the excess heat is being absorbed by the upper layer of the ocean. That’s where corals live. That is a major, major issue for coral reefs. Over the next two to three decades, as a minimum, we are going to see increased temperatures in this upper layer of the ocean because of climate change.”

On reducing our carbon footprint: 

Ku’ulei Rodgers: “The major problem is the carbon dioxide. Although there are all these new innovative solutions which are going to be important for all of us to embrace, we have to remember that all of us, even those that don’t live near the ocean, have things they can do to lessen their carbon impact. One of those things is to think about the true cost of everything that you buy. The cost to the environment, how it’s made, how far it comes from—especially here in Hawaii, where over 90% of our resources are shipped in. Another main thing you can do, easily, is to eat lower on the food chain. It takes ten times more energy every time you go up that food chain. So, it takes ten pounds of corn or soybean to make one pound of beef, or pork, and a lot of water. These are things: reduce, reuse, recycle that the public can do, that every single person as an individual can do that will make a difference to reduce our carbon.”


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