Why coral reefs could die from mass bleaching
STORY: Coral reefs around the world are turning a ghostly white amid record warm ocean temperatures.
The U.S. National Oceanic and Atmospheric Administration recently announced grim news.
(Derek Manzello, NOAA Coral Reef Watch Coordinator)
"NOAA is declaring that the world is indeed, in fact, experiencing its fourth global coral bleaching event. Significant severe coral bleaching has been reported in at least 54 countries and territories since February 2023."
Mass coral bleaching events have serious consequences for marine life and for the people and economies that rely on reefs.
Let's take a look at how global warming affects coral reefs and what the future might hold for these fragile underwater ecosystems.
Coral reefs cover just less than one percent of the ocean floor.
But they have out-sized benefits for marine ecosystems and economies.
A quarter of marine life depends on reefs for shelter and food.
Every year, coral reefs provide about $2.7 trillion in goods and services, from tourism to coastal protection.
That's according to a 2020 estimate by the Global Coral Reef Monitoring Network.
About $36 billion is generated by snorkelling and scuba diving tourists alone.
Corals have faced harsher high temperatures in 2024 than ever before, according to scientists.
And, when water temperatures rise, corals get stressed.
They cope by expelling the colorful algae living in their tissues, causing them to turn bone white.
However, not all bleached corals die, as ecologist David Obura explains.
"So bleaching is like a fever in humans. We get a fever to resist a disease. And if the disease is not too much, we recover. But if it is too much, we die as a result."
Scientists say the best chance for coral survival is for the world to cut greenhouse gas emissions to limit climate change.
But at just 1.2C of warming above pre-industrial level, some scientists think the world has already passed a key threshold for coral reef survival.
They expect between 70% and 90% of the world's coral reefs will be lost.
Scientists and conservationists are scrambling to intervene.
Conservationists are bringing coral larvae into cryopreservation banks, and breeding corals with more resilient traits.
