Hot Oceans Are Raising the Risk of Coral Bleaching Around the Globe

Bleaching in a coral reef in Papa Bay near Captain Cook, Hawaii, on September 13, 2019.
Photo: AP

Seemingly every region of the world has been breaking temperature records these days. The oceans absorb much of this heat, and it’s threatening the world’s corals.

Climate change is largely responsible for this crisis—or ourselves because, y’know, we caused this mess. Hawaii, in particular, is seeing its corals suffer this summer. Large parts of the islands and surrounding oceans just experienced their warmest summer on record compared to the historic average, according to the National Oceanic and Atmospheric Administration (NOAA). Corals are especially vulnerable to even minor increases in temperature. When the waters get too hot, corals expel their algae—which help them produce food—and they can eventually die.

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However, this bleaching extends far beyond Hawaii, Mark Eakin, a coordinator with NOAA’s Coral Reef Watch, told Earther. These high temperatures have put corals in regions from the Pacific to the Caribbean on alert. The impact stretches from north of Bermuda, through the Bahamas, and all the way to Honduras.

The last time coral bleaching happened at a global scale was during the 2014 to 2017 bleaching event. Reefs around the Samoas, Kiribati, Florida, the Caribbean, and beyond suffered heavy losses. In 2015, sites in west Hawaii lost nearly 50 percent of their coral cover, per Hawaii’s Division of Land and Natural Resources.

Now, scientists are seeing ocean temperatures rise dangerously again. Earlier this month, scientists announced a heat wave ramping up in the Pacific. It’s the second-largest heat wave recorded in the Pacific Ocean. Many of the ocean’s corals are still recovering from the damage they suffered under the 2014-17 heat wave, so the current one could be even more dangerous.

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“The biggest thing that’s driving it is climate change,” Eakin said. “All of that heat has to go somewhere, and the heat that would ordinarily go into the atmosphere has been absorbed into the upper ocean.”

This is bad.
Photo: AP
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What’s more, the Pacific heat wave is only beginning. Eakin said climate models show that heat stress may continue through November. That’s bad news for the corals, but it’s also bad news for other marine life, such as whales, seals, and salmon. The heat can hurt the food web, including humans near the top of it.

Around the world, more than half a billion people depend on reefs for food and income, as well as protection from hurricanes and storm surge. Without reefs, humans suffer.

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Unfortunately, as our world grows warmer and warmer, protecting reefs will become more difficult because they’ll have a smaller chance of bouncing back. That’s why many scientists are trying to breed “super corals,” which are resilient corals that don’t bleach as easily (or at all) during these events. The hope is that by breeding and bringing more of these into the environment, corals can evolve to better withstand this increased heat. Then, just maybe, we won’t lose coral entirely.

In the meantime, we’ll have to wait and see how reefs fare after this year’s bleaching event. Let’s hope it’s ends more quickly than the last.

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About the author

Yessenia Funes

I mostly write about how environmental policy and climate change intersect with race and class though I occasionally write about animals, science, and art, too. We all need an escape, right?

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